{"Bibliographic":{"Title":"Air Resources Laboratory 1994 Report","Authors":"","Publication date":"1993","Publisher":""},"Administrative":{"Date created":"08-16-2023","Language":"English","Rights":"CC 0","Size":"0000230933"},"Pages":["QC\n807.5\n.U6\nA72\n1994\nAIR RESOURCES LABORATORY\n1994 REPORT\nLabo r atory\nAir\nsour\nATM\nU.S. Department of Commerce\nNOAA\nNational Oceanic and Atmospheric Administration\nEnvironmental Research Laboratories\nAir Resources Laboratory\nSilver Spring, Maryland\nOF","QC\n807.5\n,46\nA72\n1994\nAIR RESOURCES LABORATORY\n1994 REPORT\nAugust 1995\nOF\ncompany\nU.S. Department of Commerce\nNational Oceanic and Atmospheric Administration\n*\n*\nEnvironmental Research Laboratories\nWITH\nAvenue\nAir Resources Laboratory\nSilver Spring, Maryland\nSTATES\nOF\nJAN 15 1996\nN.O.A.A.\nU.S. DEPT. OF COMMERCE","Notice\nMention of a commercial company or product does not\nconstitute an endorsement by NOAA's Environmental\nResearch Laboratories. Use for publicity or advertising\npurposes of information from this publication concerning\nproprietary products or the tests of such products is not\nauthorized.\nThis document was prepared during early 1995 by the\nNational Oceanic and Atmospheric Administration,\nEnvironmental Research Laboratories,\nAir Resources Laboratory.\nFor sale by the National Technical Information Service, 5285 Port Royal Road\nSpringfield, VA 22061","From the Director\nThe Air Resources Laboratory (ARL) is a scientific\norganization with a rich history and a keen eye towards the\nfuture. We now step into our 47th year as leaders in\nvarious aspects of applied air quality and climate research\nwith increased recognition that national needs are\nchanging, and in anticipation of emerging scientific\nquestions that will challenge our skills and resources. We\nlook forward to these challenges, with awareness that new\nenvironmental issues will tend to be cross-disciplinary, and\nmulti-media. A conclusion that might follow remains to be\ntested - that the days of ever-narrowing environmental\nspecialization are possibly over. Certainly, the Air\nResources Laboratory will continue in its historic role of\nstretching the ability to predict, forecast, and/or assess, in\nall areas where the air interacts with other components of\nthe environment.\nThis report presents some of our recent accomplishments\nand our vision for the future. There has been no attempt\nto be exhaustive; rather the goal has been to focus on\nareas of significant activity specifically related to the NOAA\nStrategic Plan or involving more than one of the ARL\ndivisions. As in the past, each item that is summarized is\nnot intended to answer all of the readers' questions, but\ninstead to whet their appetite for more information, which\nwe would be happy to provide.\nMuch of our effort involves collaborative research and\nsupports other government agencies and programs. So we\nare particularly sensitive to trends in, and the requirements\nof, the community with which we interact.\nYour\ncomments about ARL or this report are always welcome.\nBruce B. Hicks, Director\nTelephone (301) 713 0684\nAir Resources Laboratory\next 136\nNOAA/SSMC3, Room 3152\nFAX\n(301) 713 0119\n1315 East West Highway\nE-Mail\nhicks@arlrisc.ssmc.noaa.gov\nSilver Spring, MD 20910","In Memoriam\nTERRY L. CLARK (1950-1994)\nTerry Lee Clark, 43, of Cary, NC passed away on January 28,\n1994, from complications of Acquired Immune Deficiency\nSyndrome. Born in Baltimore, MD, Terry graduated with a BS\nand MS in Meteorology from Texas A&M. Since 1975, Terry\nhad been with NOAA/ARL as a research meteorologist assigned\nto ASMD in Research Triangle Park, NC. During this period, he\nwas very active in scientific research, developing and applying\nmodels of air pollution dealing with a wide range of issues\nincluding visibility, and acid and toxics deposition. Terry\ndeveloped and applied the Regional Lagrangian Model for Air\nPollution (RELMAP). During the NAPAP years, he led the\nworking group \"International Sulfur Deposition Model Evaluation\"\n(ISDME) program. He also played a key role in designing and\nimplementing an EPA toxics modeling effort in response to the\nGreat Waters Study which was mandated in the 1990 Clean Air\nAct Amendments. Terry earned the respect and admiration of\nhis colleagues and of the international air pollution modeling\ncommunity.","Table of Contents\nAn Overview of ARL\n1\nRecent Accomplishments - Program Highlights of ARL Research\nTheme - Air Quality and Dispersion\nA New NOAA Aircraft Capability\n11\nARL High-Latitude Studies\n13\nAir-Surface Exchange\n17\nThe Atmospheric Integrated Research Monitoring Network (AIRMoN)\n19\nAIRMoN-Wet\n21\nAIRMoN-Dry\n23\nAIRMoN & Early Detection\n25\nCoastal Ecosystem Atmospheric Loadings\n27\nNitrogen Deposition to the Chesapeake Bay\n31\nModels-3\n35\nOzone Research in ARL\n37\nTheme - Climate Trends and Variability\nAerosol Studies\n41\nErosion, and Resuspension of Surface Particles\n43\nClimate Change and the IPCC\n45\nISIS\n49\nAtmospheric Optics\n51\nTheme - Emergency Preparedness\nAtmospheric Tracer Studies\n53\nDispersion Studies\n55\nStudies of Nocturnal Dispersion\n57\nAircraft Wake Vortices\n59\nFluid Modeling\n61\nHeavy Gas Dispersion\n63\nRSMC Washington\n65\nThe VAFTAD Model\n67\nInternational Programs and Activities\nA WMO/GAW Science Activity Center for the Americas\n69\nInternational Activities\n73\nARL 1994 Publications\n75","An Overview of ARL\nMission:\nWeather Bureau, in 1948. In 1963 (and\nuntil 1965), its name was changed to the\nAlthough ARL, probably more than most\nMeteorological Research Projects Branch of\nother NOAA laboratories, works closely\nthe Weather Bureau. In 1965, the\nwith other government agencies, we are\norganization (including its field offices) was\nfirst and foremost a NOAA research\nreconstituted as the Air Resources\nlaboratory. As stated in the NOAA\nLaboratories, and most recently (1981)\n1995-2005 Strategic Plan, \"NOAA's\nwas redefined as a single Air Resources\nmission is to promote global environmental\nLaboratory with several field divisions.\nstewardship and to describe and predict\nThus, ARL is not a single, centrally-located\nchanges in the Earth's environment. The\nlaboratory, but a consolidation of spatially\nARL contribution to that goal can be\ndistributed laboratories that focus on\nsummarized in the ARL mission statement:\nspecific aspects of research related to the\noverall ARL air quality mission.\nThe Air Resources Laboratory carries out\nresearch on processes that relate to air\nOn 22 January, 1994, the formal transfer\nquality and climate, concentrating on the\nof the National Weather Services Nuclear\ntransport, dispersion, transformation and\nSupport Office in Las Vegas to ARL was\nremoval of trace gases and aerosols, and\ncompleted. The new ARL Las Vegas group\nthe exchange between the atmosphere and\nis known as the Special Operations and\nbiological and non-biological surfaces. The\nResearch Division.\ntime frame of interest ranges from minutes\nand hours to that of the global climate.\nARL's approximately 130 federal\nResearch in all of these areas involves\nemployees work in laboratories in six\nphysical and numerical studies, leading to\nstates, as follows.\nthe development of air quality simulation\nmodels. The Laboratory provides scientific\nHeadquarters Division\nadvice to elements of NOAA and other\n(Silver Spring, MD)\nGovernment agencies on environmental\nFocus: Transport, wet deposition, and\nproblems, emergency assistance, and\nclimate change\nclimate change.\nAtmospheric Sciences Modeling Division\nThe specific goal of ARL research is to\n(Research Triangle Park, NC)\nimprove and eventually to institutionalize\nFocus: Integrated modeling\nforecasting of air quality, deposition, and\nDirector: Frank Schiermeier\nrelated atmospheric environmental\nvariables. This is in support of concerns\nAtmospheric Turbulence and Diffusion\nrelated to effects on human health,\nDivision (Oak Ridge, TN)\necosystem viability, sustainable\nFocus: Turbulent dispersion and exchange\ndevelopment, and international\nDirector: Ray Hosker\ncompetitiveness.\nField Research Division\nPersonnel and Divisions:\n(Idaho Falls, ID)\nFocus: Air quality transport and model\nThe Air Resources Laboratory started as\nevaluation\nthe Special Projects Section of the U.S.\nActing Director: Gene Start","Special Operations and Research Division\nEmergency Preparedness (nuclear;\n(Las Vegas, NV)\nvolcanoes; toxics; dense gases)\nFocus: Particle dispersion and deposition,\nIn every case, the end product of ARL\nemergency response\nDirector: Darryl Randerson\nresearch is an improved capability to\npredict some aspect of air quality. This\nIn 1994, the Aerosol Research Section in\ncapability will necessarily take the form of\nBoulder was disbanded, and a new Surface\na computer model of some kind, driven by\nRadiation Research Branch was formed\nmeteorological information and emission\nunder the leadership of Dr. John DeLuisi\ndata, and containing the best available\nand as a field component of the\ndescriptions of all relevant processes. To\nHeadquarters Division.\nthis end, ARL conducts research involving\nboth modeling and measurements, with an\nMajor Awards\nemphasis on integration of these activities.\nIt is recognized that modern models are\nASMD scientists Alan Huber, John\ninvariably data assimilative, and that\nStreicher, and Gennaro Crescenti were\nmodern monitoring programs require\nawarded NOAA Bronze Medals for their\ncoupled modeling activities for data\nwork in Thailand. Their project provided\ninterpretation.\nthe Royal Thai Government with modeling\nand monitoring results to assist in\nThe applications of these capabilities range\nmanaging air quality at the Mae Moh Power\nfrom assessment, typically using\nPlant to minimize the possibility of future\nclimatological or \"characteristic\" inputs, to\nacute effects on health and vegetation. At\nshort-term prediction, based on the use of\nan EPA Awards Ceremony on November\nmeteorological forecast data. The current\n22, Ken Schere of ASMD was awarded\nstate of this science is that different\ntwo EPA Bronze Medals, one for his earlier\napplications require different mixes of the\nwork in developing the case for NOX as well\nprocesses to be considered, and it is\nas VOC controls for ozone reduction, and\nanticipated that future products will retain\nanother for his assistance in organizing the\nmuch of this specialization. In this context,\nNorth American Research Strategy for\nhowever, there is an over-riding recognition\nTropospheric Ozone (NARSTO).\nof the need for model products to be as\nsimple as satisfies the demands placed on\nResearch Philosophy:\nthem, while being adequately complete in\ntheir formulation. The models are intended\nScientific investigations conducted by ARL\nto be parsimonious, data assimilative, and\nlocations are coordinated and organized in\nregularly benchmarked against observations\nthree themes. The accomplishments\nmade with coupled observing networks.\ndescribed in the body of this report are\nTo this end, the organizational components\norganized according to these themes:\nof ARL contribute in the following fashion.\nAir Quality and Dispersion (air-surface\nDeveloping Models\nexchange; acid deposition; ozone and\noxidants; aerosols and visibility)\nImproving model assessment\ncapabilities for support of regulations and\nClimate Trends and Variability (solar\ncontrols - Research Triangle Park\nradiation, including infrared and\nultraviolet; meteorological trends;\nEnhancement of site-specific, air-quality\ndesertification)\nmodels - Oak Ridge\n2","Determining the relationship between\nthe administration, the Congress, various\npollutant concentrations and deposition -\nstate and federal agencies, the public,\nOak Ridge\nprivate industry, and the scientific\ncommunity.\nLinking air quality and deposition models\nwith routine forecast products - Silver\nIn this regard, ARL strives to be a full-\nSpring\nservice organization, supporting necessary\nresearch at selected universities,\nExtending modeling and assessment\nmaintaining a long-term monitoring and\nwork to radioactivity - Las Vegas\nanalysis infrastructure around which the\nresearch is concentrated, and representing\nProviding emergency response\nNOAA and the national interest in policy\ncapability for nuclear and toxic materials -\ndebates and scientific discussions on\nLas Vegas, and Silver Spring\nrelated matters.\nField testing and evaluating models -\nA central issue is the relationship of ARL\nIdaho Falls\nwith other laboratories in NOAA, especially\namong the Environmental Research\nProvision of Data\nLaboratories. But equally important is the\nrole that has developed involving other\nEnsuring the compatibility of\nagencies. In practice and by intent, ARL is\ninternational data sets - Silver Spring\nthe major point of interaction between\nNOAA atmospheric research and the\nAccounting for poor measurement\nrelated informational and scientific\nfidelity - Silver Spring\nrequirements of several other agencies.\nOperating integrated networks to couple\nNOAA is viewed by other agencies as a\nmonitoring observations with model\nprovider of high-quality and independent\npredictions (AIRMoN) - Silver Spring, Oak\nadvice regarding matters of atmospheric\nRidge\ntransport, dispersion, air quality, and\ndeposition, and ARL is perceived to be the\nOperating networks to characterize data\nagent providing access to this advice.\nfields required as input for air quality,\nsurface energy balance, solar radiation, and\nNOAA values independence from\ndeposition models - Oak Ridge, Boulder,\nagencies that are more closely influenced\nResearch Triangle Park\nby policy and regulatory considerations,\nand attributes (in part, at least) the high\nProviding quality assurance on national\nquality of its science to the opportunity to\nradiation data (solar, surface, UV-B) -\nconduct and promote research\nBoulder\nindependently of policy and regulatory\nprocesses.\nARL's Role in the Federal Government:\nMuch of the contribution made by ARL can\nARL conducts research as needed to\nbe viewed as provision of independent\nanswer questions of urgency related to\natmospheric expertise to assist other\nregulatory controls and policy, public\nagencies in fulfilling their own federal\nsafety, and the environment (as it involves\nmandates. This provision of scientific\natmospheric considerations). ARL serves\ninformation and advice to other agencies\nas a provider of scientific information to\ncan be considered to be a component of\n3","NOAA's service function. Financial support\nNOAA's role as a source of atmospheric\nfor work intended to permit another agency\nand aquatic environmental guidance to\nto perform its own function, in its own\nother elements of society and especially to\njurisdictions, with improved credibility and\nother federal agencies, independent of their\ndefensibility is normally provided by the\nown regulatory and control functions. ARL\nother agency concerned. At this time, the\nresearch contributes directly in several\nmajor agencies involved are the\nNOAA Strategic Plan components, as\nEnvironmental Protection Agency and the\nfollows.\nDepartment of Energy. ARL is roughly\nequally supported by NOAA, EPA, and\nCoastal Ecosystems Health\nDOE.\n(a)\nThe role of atmospheric deposition as\nThe Environmental Protection Agency\ncontributor to coastal ecosystem\na\nprovides almost complete support for the\neutrophication and decay.\nARL team at Research Triangle Park,\nestablished specifically to provide\nARL is conducting research to develop\nmeteorological expertise and services to\nobjective methods for quantifying\nEPA, related to atmospheric dispersion and\natmospheric deposition, as it affects\nair quality modeling.\ncoastal ecosystems, with emphasis on\nnutrients and toxics. Current research is\nThe Department of Energy provides\ndirected specifically to the roles of nitrates\nabout 25% of the funding for the ARL\nand airborne toxic chemicals. ARL is\nteam at Oak Ridge, set up to provide a\nfocussing initially on East Coast\ncollaborative NOAA/DOE capability to\necosystems - mainly the Chesapeake Bay\naddress questions on dispersion, deposition\nand Albermarle/Pamlico Sound. State-of-\nand air quality of relevance to the DOE Oak\nthe-art models are being developed by ARL\nRidge Field Office.\n(Research Triangle Park), and advanced\nmeasurement systems are being deployed\nThe Department of Energy also provides\nby ARL (Oak Ridge and Silver Spring).\nabout 25% of the funding at Idaho Falls,\nInitial estimates for the Chesapeake Bay\nfor maintenance and improvement of\nindicate that about 30-40% of the nitrogen\nemergency assistance services to the Idaho\nloading is derived from the atmosphere.\nNational Engineering Laboratory.\nARL chairs the Chesapeake Bay Air Quality\nCoordination Committee, an officially-\nThe Department of Energy provides\nendorsed body for consolidating activities\nalmost all of the funding of the ARL Special\namong federal and state agencies.\nOperations and Research Division, in Las\nVegas, to support the DOE defense\n(b) Monitoring of Causative Factors.\nprograms of the Nevada Operations Office.\nARL is leading a national thrust towards\nARL's Contribution to the NOAA Strategic\n\"integrated monitoring,\" a new multi-\nPlan:\ndisciplinary approach to monitoring to\naddress complex questions. Since\nThe NOAA Strategic Plan focuses on needs\nmonitoring of the actual health of\nthat are related to the performance of\necosystems only provides indications of\nNOAA's own mission. The activities of\ndamage after the damage has occurred,\nARL contribute to the goals of the Strategic\nresponsible ecosystem monitoring requires\nPlan, but also interject the requirement to\nattention to those factors that cause the\nconsider a higher plane of consideration -\ndamage to occur, specifically input rates of\n4","toxic materials and nutrients. The present\nmodels. In the future, data assimilation\nobjective is to develop cost-effective and\nmethods must be extended, to focus on\nproven methodologies for conducting such\nareas where forecasts are specially needed.\nmonitoring.\n(b) Emergency Planning and Response\nARL operates exploratory monitoring\nstations in coastal areas, where\nARL serves as a center of activity for the\ninterpretation of atmospheric data is\nprovision of specialized meteorological\npresently difficult and agreement on the\nassistance in the event of large releases of\nresults is rare. Techniques are being\nhazardous materials into the atmosphere,\ndeveloped to account for the roles of\nsuch as from volcanoes, nuclear accidents,\nterrain complexity in the models used to\nand industrial disasters. In general, NOAA\ninterpolate among monitoring sites and in\nprovides basic meteorological support in all\nthe simulations used to assess likely inputs\nsuch cases, but is also expected to provide\nin the absence of field data. In particular,\nrelated guidance to other agencies and\ntechniques to account for moderate terrain\nwarnings to the public. For this purpose,\ncomplexity have been developed and are\nARL (as a joint activity with the National\nnow being included in assessment models\nMeteorological Center) operates a Regional\nbeing developed by ARL for EPA. As yet,\nSpecialized Meteorological Center for the\nthere has been no opportunity to test the\nWorld Meteorological Organization (WMO),\npredictions of these models against field\nto provide emergency response assistance\nto the nations of North and Central\ndata, however steps to provide a platform\nsuitable for collecting such data have been\nAmerica in the event of a disastrous\natmospheric accident. Throughout the\ninitiated.\nentire nuclear era, ARL has provided\nAdvance Short-Term Warning and Forecast\nemergency preparedness and response\nservices to DOE and the Nuclear Regulatory\nServices\nCommission (NRC), relating to nuclear\naccidents and explosions and to the\n(a) Air Quality Predictions\nunderground testing of nuclear weapons.\nA major goal of ARL is to develop the basis\non which to extend current prediction\nAs components of this activity, ARL\nservices to other environmental variables,\ncoordinated much of the multi-agency and\nnecessitated by increasing population and\nmulti-national atmospheric research\nsocietal pressure. The long-term goals of\nresponse to the Kuwait oil fires emergency.\nARL developed the techniques now in\nthis research are related to assessing air\nroutine use for forecasting the spread of\nquality (ozone, particulates, etc.) and to\nvolcanic ash. ARL also developed the\nUV-B radiation.\nmethodologies now in place to advise NRC\n(and several components of DOE) in the\nIn this context, it is apparent that the focus\nof most atmospheric predictive models is\nevent of a nuclear accident. In the distant\npast, ARL research led to the generation of\non those layers of the atmosphere that\nthe now famous \"Gaussian plume\"\nmove weather systems. For air quality,\ndispersion methodology, now routinely\nmore attention must be directed to the\nused for warning the nearby public in the\nlower atmosphere (where people live and\nwhere pollution is greatest). Relevant\nevent of a leak of trace quantities of\nmodels are now available, and are slowly\nhazardous gases into the atmosphere.\nbeing coupled with weather forecasting\n5","Seasonal to Interannual Climate Forecasts\nand assessment models will need to\nbroaden their scope from countries to\n(a) Air Quality and Environmental\ncontinents.\nAssessments\nPredict and Assess Decadal-to-Centennial\nAs a longer-term extension of ARL's work\nChange\non air quality prediction, ARL provides\nobjective and independent guidance to\n(a) Detection and Attribution of Change in\npolicy-makers concerning specific\nAir Quality\nenvironmental concerns and corresponding\nregulatory strategies, related to national\nA major component of ARL research relates\nand global air quality and climate. Specific\nto the need to detect the consequences of\nexamples of recent issues include acid rain,\nimposed emission controls in a timely and\ntropospheric ozone, visibility, and airborne\nunequivocal manner, so as to permit\ntoxics.\nremedial adjustments in control strategies.\nFor this reason, ARL has operated a\nNOAA/ARL provides independent guidance\nresearch-grade national monitoring network\non alternative regulatory and control\nsince about 1984, concentrating on\nstrategies to the EPA through its Research\nchemicals indicative of industrial and\nTriangle Park operation. ARL also conducts\nsocietal emissions - primarily sulfur and\nextensive field tests of the models\nnitrogen oxides. Recently the longest-\ndeveloped for such purposes, through its\nrunning precipitation chemistry network in\nIdaho Falls group.\nthe world has been consolidated with this\nARL program. Now, we have an ongoing,\nFor more than a decade, NOAA has\nbroad-based network that is specifically\nprovided the scientific direction of the\ndesigned to reveal changes in the\nNational Atmospheric Precipitation\natmospheric environment, with rapidity.\nAssessment Program, an interagency body\nto provide necessary cross-agency\nAt this time an Atmospheric Integrated\nmechanisms to coordinate research,\nResearch Monitoring Network (AIRMoN)\nconsolidate knowledge, integrate\nexists, although in embryonic form. The\nassessments, and implement national\nmodels that are needed to interpret the\nstrategies. ARL has been the principal\ndata obtained are also on hand, although\nNOAA representative.\nonly as first-generation attempts as yet.\nThe existing AIRMoN program is designed\nIn collaboration with scientists from many\nprimarily to provide accurate information on\nother agencies, ARL has led scenario-based\nthe rate of deposition of air chemicals to\nassessments of toxic chemicals, ozone,\nthe surface; present planning is to add a\nand NOX control options, etc.\nThe\nrapid detection component to the AIRMoN\nimportance of this activity is rapidly\nprogram, under funding through the new\ngrowing. NOAA is widely viewed as an\nHealth of the Atmosphere program. The\nindependent source of expert information\nintentions are that the AIRMoN will be\non matters of environmental and air quality\nrefined and coupled with real-time analysis\npolicy, both nationally and globally. As\nand modeling so as to reveal those changes\ntime progresses, environmental quality is\nthat can be attributed to changes in\nbecoming less of a local problem and more\npollution emissions.\nof a global concern. Air quality scenario\n6","(b) Quality Assurance of Global Data\naccidental, as we try to use our collective\nscientific experience and training to\nARL leads a multi-national effort to ensure\nencourage young people's interest in the\nthat air quality data sets collected by\nnatural world.\nnational monitoring networks can be\nbrought together in an objective and\nARL scientists serve as Adjunct Professors\nat the following universities and colleges:\nseamless manner. A WMO Quality\nAssurance/Science Activity Center for the\nAmericas is presently being inaugurated, to\nDuke University\nserve North, Central, and South America.\nGeorgia Institute of Technology\nThe center will work directly with member\nHebrew University (Jerusalem)\nnations, and with site operators, to ensure\nNorth Carolina State University\nthe highest possible integrity of monitored\nUniversity of Nevada at Las Vegas\ndata. A three-agency consortium has been\nUniversity of North Carolina\nUniversity of Tennessee at Knoxville\nestablished to provide the necessary\nsupport - DOE, EPA and NOAA.\nCarlos Alicea, a Hispanic summer intern,\nworked with ARL/HQ from 6 June to 12\nRecent Organizational Highlights\nAugust. Carlos' background is in\nIn keeping with government-wide efforts to\nEnvironmental Science.\nstreamline programs and provide higher\nVeronique Bugnion visited SRRB as part of\nquality and more cost-effective service to\nthe DOC/NOAA Exchange Visitor Program\nthe nation, the Air Resources Laboratory\n(a program of the DOC/NOAA to provide\nhas recently re-aligned its research\ncourses of study at selected universities,\ncapabilities, facilities and personnel to\netc., for qualified foreign students.)\nstrengthen operations in areas where we\nare widely seen to have special skills and\nTwo high school students were supported\nto refocus efforts towards scientific issues\nby ATDD through the Anderson County\nof national and international importance.\nMajor changes involved restructuring the\nschool system vocational education\nprogram. Two additional students were\nARL presence in Boulder and establishing\nan integrated surface radiation program\nadded for the summer.\nthere; centralizing surface dust activities in\nGlenn Rolph and Rick Artz continued to\nResearch Triangle Park, and aircraft\nparticipate in the National Geographic Kids\nactivities in Oak Ridge; and welcoming\nNetwork on Acid Rain. Glenn and Rick\nback into the ARL family the NOAA/NWS\nprovide assessments of the data collected\nNuclear Support Office in Las Vegas,\nin North America and abroad by elementary\nNevada.\nschool students. Students learn about\natmospheric deposition, collect\nOutreach and Community Service\nobservations, and analyze the results.\nThe Air Resources Laboratory promotes the\nThe following schools were involved in ARL\nideals of equality of opportunity, good\nneighborliness, and community service in\noutreach programs -\nits official activities and the private lives of\nKirk of Kildaire Preschool, Cary, NC\nits staff members. Here we list just a few\nCresthaven Elementary, Washington, DC\nof the contributions of the laboratory and\nEno Valley Elementary, Durham, NC\nits employees during 1994. The heavy\nMemorial Elementary, Paris, IL\nemphasis on science education is not\n7","West Hills Elementary, Knoxville, TN\nWoodland Elementary, Oak Ridge, TN\nLinden Elementary, Oak Ridge, TN\nClark County School District, Las Vegas,\nNV\nBonneville School District, Idaho Falls, ID\nBoulder Junior High, Boulder, CO\nSORD employees participated in Native\nAmerican Program in November, Veterans\nDay Program in November, and Angel Tree\nProject in December. In addition, SORD\n(Las Vegas) participated in the Partnership\nin Education program, involving visits to\neight schools.\nSORD also participated in the DOE\nsponsored \"Science Now\" program in Las\nVegas. This focused on outstanding high\nschool students from the Las Vegas area.\nStudents were given the opportunity to\noperate NOAA equipment and to interact\nwith NOAA meteorologists.\nATDD (Oak Ridge) again participated in the\nannual DOE and Martin Marietta Energy\nSystems-sponsored \"Environmental Fair.\"\nLocal businesses and organizations\nparticipated in an effort to educate grade\nschool students about various\nenvironmental issues. ATDD's booth\npresented information about current global\nclimate change studies, and contained\nseveral \"hands-on\" demonstrations.\nATDD also hosted about 100 local fourth\ngrade students at a presentation on\nlatitude, longitude, and use of the Global\nPositions System (GPS) to determine\nlocation, as part of the National Geographic\nprogram for students to determine their\n\"global address\" for inclusion in an\nInternet-accessible database.\nAt Research Triangle Park, Dr. Sharon\nLeDuc gave a Career presentation to\nseventh grade students, at the University\nof North Carolina, Chapel Hill, NC.\n8","List of Acronyms\n- Atmosphere-Ocean Chemistry Experiment\nAEROCE\n- Atmospheric Integrated Research Monitoring Network\nAIRMoN\n- Across North America Tracer Experiment\nANATEX\n- Atmospheric Nutrient Input to Coastal Areas\nANICA\n- Air Quality Simulation Models\nAQSM\n- Air Resources Laboratory\nARL\n- Atmospheric Radiation Measurement program\nARM\n- Atmospheric Sciences Modeling Division\nASMD\n- Atmospheric Turbulence and Diffusion Division\nATDD\n- Background Air Pollution Monitoring Network\nBAPMoN\n- Boreal Ecosystem-Atmosphere Study\nBOREAS\nCAPTEX\n- Cross-Appalachian Tracer Experiment\nCART\n- Cloud and Radiation Testbed\nCASTNET\n- Clean Air Status and Trends Network\n- Collocated Operational Research Establishments\nCORE\n- Cray Research Adaptive ForTran\nCRAFT\n- Complex Terrain Dispersion Model\nCTDM\n- Dry Deposition Inferential Monitoring\nDDIM\nDOE\n- Department of Energy\n- Environmental Protection Agency\nEPA\n- Emission Processing System\nEPS\nETEX\n- European Tracer Experiment\nFAA\n- Federal Aviation Administration\nFRD\n- Field Research Division\n- Flexible Regional Emissions Data System\nFREDS\n- Global Atmosphere Watch\nGAW\n- Geocoded Emission Modeling and Projection\nGEMAP\nGPS\n- Global Positioning System\n- Global Telecommunications System\nGTS\n- High Performance Computing and Communications\nHPCC\n- Hybrid Simple Particle Lagrangian Integrated Trajectory model with\nHYSPLIT-ACID\nAtmospheric Chemistry Including Deposition\n- International Atomic Energy Agency\nIAEA\n- International Global Atmospheric Chemistry\nIGAC\n- Intergovernmental Panel on Climate Change\nIPCC\n- Infrared gas analyzer\nIRGA\n- Industrial Source Complex - COMPlex terrain DEPosition\nISC-COMPDEP\n- Integrated Surface Irradiance Study\nISIS\n- Multistate Atmospheric Power Production Pollution Study\nMAP3S\nMAS\n- Mobile Atmospheric Spectrometer\n- Mobile Flux Platform\nMFP\n- Medium Range Forecast\nMRF\n- National Ambient Air Quality Standards\nNAAQS\n- National Atmospheric Deposition Program\nNADP\n- National Acid Precipitation Assessment Program\nNAPAP\n- North Atlantic Regional Experiment\nNARE\n- National Aeronautics and Space Administration\nNASA\n9","NARSTO\n- North American Research Strategy for Tropospheric Ozone\nNAWC\n- Navy Air Warfare Center\nNESDIS\n- National Environmental Satellite, Data, and Information Service\nNIST\nNational Institute of Standards and Technology\n-\nNMC\n- National Meteorological Center\nNMFS\n- National Marine Fisheries Service\nNOAA\n- National Oceanic and Atmospheric Administration\nNRC\n- Nuclear Regulatory Commission\nNSF\n- National Science Foundation\nNTS\n- Nevada Test Site\nNWS\n- National Weather Service\nPBL\n- Planetary Boundary Layer\nPERF\n- Petroleum Industry Environmental Research Forum\nPVM\n- Parallel Virtual Machine\nQA/SAC\n- Quality Assurance/Science Activity Center\nQAPJP\n- Quality Assurance Project Plan\nQBO\n- Quasi-Biennial Oscillation\nRADM\n- Regional Acid Deposition Model\nRAMAN\n- Regional Atmospheric Measurement and Analytical Network\nRAMS\n- Regional Atmospheric Modeling System\nRELMAP\n- Regional Lagrangian Model of Air Pollution\nROM\n- Regional Oxidant Model\nROSE\n- Regional Oxidants in the SouthEast\nRSMC\n- Regional Specialized Meteorological Centre\nRTP\n- Research Triangle Park\nSORD\n- Special Operations and Research Division\nSPARC\n- Stratospheric Processes And their Role in Climate\nSRRB\n- Surface Radiation Research Branch\nSURFRAD\n- Surface Radiation monitoring network\nTOGA/COARE\n- Tropical Ocean Global Atmosphere/Coupled Ocean-Atmosphere Response\nExperiment\nUSGS\n- U.S. Geological Survey\nUV-B\n- Ultraviolet-B\nVAFTAD\n- Volcanic Ash Forecast Transport and Dispersion\nWATOX\n- Western Atlantic Ocean Experiment\nWBW\n- Walker Branch Watershed\nWMO\n- World Meteorological Organization\nWTI\n- Waste Technology Industries\n10","AIR QUALITY AND DISPERSION\nA NEW NOAA AIRCRAFT CAPABILITY\nThe Twin Otter Airborne Mobile Flux Platform\nBackground.\nplaces severe constraints on the design and\ndeployment of the appropriate sensors.\nThe NOAA Strategic Plan promotes the\nneed to predict with accuracy short-term\nDue to the complexities involved, eddy flux\nenvironmental changes, and recognizes\nmeasurement campaigns often use\nthat current understanding is restricted by\nstationary sensors affixed to ground-based\nobservations that are temporally and\nmeteorological towers. While these tower-\nspatially incomplete. Purchase during\nbased measurements yield detailed\n1994 of a de Havilland Twin Otter aircraft\ninformation on the surface exchange\nby the NOAA Aircraft Operations Center,\nprocesses at a single location, they reveal\nusing funds from ERL, ARL and the\nlittle about the representativeness of the\nNational Marine Fisheries Service, is\nmeasurements in the larger geographical\nintended to allow the Air Resources\ncontext, or about the spatial variability of\nLaboratory to address this issue by\nthe exchange process. For spatially\nimproving our current flux measurement\nresolved information, measurements from\ncapability and by providing a slow, stable\ninstrumented research aircraft are required.\nplatform for the collection of atmospheric\nFlux measurements from aircraft, however,\nchemistry data. It is expected that the\nare rendered more complicated by\nTwin Otter will occupy a unique niche in\nstreamline deformation considerations,\nNOAA's atmospheric research capabilities--\ncoupled with the requirements to\nan aircraft suited for flux and atmospheric\naccurately measure air motions relative to\nchemistry missions in the lower\nthe airframe and aircraft motions relative to\ntroposphere at a low operational cost.\nthe ground.\nTower and Aircraft Platforms.\nThese measurement demands have been\nmet by ARL's development of a Mobile Flux\nMeasurements of surface exchange\nPlatform (MFP). The MFP offers\n(turbulent flux) processes constitute a\nconsiderable advantages over traditional\nmajor research activity of NOAA's Air\nflux measurement packages, which are\nResources Laboratory (ARL). A \"first\nexpensive and require significant space and\nprinciples\" method for turbulent flux\npower, limiting their use to larger aircraft\nmeasurements is eddy covariance, or eddy\nwith attendant increases in flow\ncorrelation. In this method fast response\ndisturbance. The miniaturized sensors in\nmeasurements of trace species (e.g., H2O,\nthe MFP allow collocation of the motion\nCO2, O3) are combined with fast response\nand velocity sensors in the instrument\nmicrometeorological measurements (3-\nprobe affixed to the aircraft, which centers\ndimensional winds, temperature) to directly\nthe frame of reference in the probe (rather\ndetermine the species flux to or from the\nthan in the aircraft), simplifying the\nsurface. While the technique is simple in\nmathematics required to separate probe\nconcept, in reality it places stringent\nand air motions. Its light weight and low\ndemands on the measurement system.\npower consumption allow the MFP to be\nChief among these is the requirement that\ninstalled in small aircraft and other low\nstreamline deformation caused by the\noperating cost vehicles.\nsensors themselves be minimized. This\n11","AIR QUALITY AND DISPERSION\nthe payload capacity of the Twin Otter,\nARL Aircraft Programs.\nwhich will allow the deployment of more\nTwo aircraft have been used in recent\ncomplete measurement suites. The major\nyears to support ARL's research programs.\ndrawbacks of the Twin Otter include a\nThe prime demonstration platform for the\nlimited range (< 1000 km) and ceiling (5.5\nMFP has been a staff-owned variant of the\nkm). These limitations will not pose\nRutan-designed \"Long-EZ\" airplane. The\nserious problems for atmospheric research\nLong-EZ is a high efficiency airframe with\nin the boundary layer and lower free\na \"pusher\" engine configuration which\ntroposphere, the regions of interest for the\nleaves the nose of the airplane free from\nmajority of ARL programs.\npropeller-induced flow disturbances, engine\nvibration, and exhaust. The aircraft's\nThe 1994 Purchase.\nsuperior pitch stability and low wing\nloading allow safe, low speed flight at 50\nThe 1994 purchase of a previously-leased\nm/s, reducing flow compressibility\nTwin Otter by NMFS and ERL will allow the\ndisturbances far below those typical of fast\ndeployment of the aircraft in FY 1995 for\ntwin engine aircraft. The Long-EZ,\nuse in a variety of atmospheric research\nhowever, is a developmental airframe with\nprograms involving several ERL\nminimal (70 kg) instrument payload\nlaboratories. Flux measurements and\ncapacity, and is capable of carrying only\natmospheric chemistry studies are currently\nthose sensors which are compact,\nrequired for several broad-based programs\nlightweight, and completely automated.\nsupported by NOAA and other scientific\nARL's second aircraft, a Beechcraft King\norganizations. Programs which require the\nAir C-90, has been used extensively in the\nuse of the Twin Otter include the\npast for air quality and atmospheric\nAtmosphere-Ocean Chemistry Experiment\nchemistry studies. While the King Air is an\n(AEROCE), and various programs of the\nexcellent platform for weather modification\nNorth American Research Strategy on\nand some air quality experiments, its\nTropospheric Ozone program (specifically\npayload capacity is frequently insufficient\nduring 1995, the Southern Oxidants\nfor detailed studies of tropospheric\nStudy). In addition, participation in\nphotochemistry. In addition, the King Air is\nBOREAS, GEWEX, and wake turbulence\ninadequate for turbulent flux\nstudies is anticipated. Other ERL\nmeasurements, as its less streamlined\nlaboratories which have expressed interest\ndesign and faster flight speeds result in\nin the Twin Otter include the Environmental\nunacceptable flow distortion around the\nTechnology Laboratory and the National\nairframe.\nSevere Storms Laboratory.\nThe aircraft of choice for many eddy flux\nAt the end of 1994, work started in\nand gradient studies is a DeHavilland Twin\nearnest on modifying the aircraft for use as\nOtter, a twin engine, non-pressurized, high\na flux platform (both eddy fluxes and PBL\nwing aircraft that combines the slow,\ngradients). Some of the modifications (to\nstreamlined flight characteristics of the\nthe airframe, power, navigation systems,\nLong-EZ with a payload capacity more than\netc.) were performed by staff of the Navy\ntwice that of the NOAA King Air. Thus the\nAir Warfare Center (NAWC) in Warminster,\naircraft will be uniquely suited to permit\nPA. Most of the ARL effort was provided\naccurate eddy flux measurements of a\nthrough the groups at Oak Ridge, Boulder,\nvariety of trace species, including those\nSilver Spring, and Idaho Falls.\nwhich require heavy and complex detection\ninstrumentation. Trace gas and aerosol\nphotochemistry studies will benefit from\n12","AIR QUALITY AND DISPERSION\nARL HIGH-LATITUDE STUDIES\nBOREAS, and the Alaskan North Slope\nBackground.\nDuring the second field campaign, a 100\nmm rainfall event was followed by several\nThere is considerable uncertainty about the\nweeks of warm dry weather. After the\nway in which high-latitude ecosystems are\navailable surface water evaporated, high\ndescribed in numerical models.\nFor\ntemperatures and high vapor pressure\nexample, it is not clear how much carbon\ndeficits forced stomata to restrict\ndioxide is sequestered in Arctic\ntranspiration. Hence, most energy\necosystems, or how much methane or\nappeared as sensible heat. Net daily\nnitrogen oxides emanate from them.\ncarbon fluxes were small and sometimes\nMoreover, even the simplest considerations\nrepresented a loss from the ecosystem.\nof surface energy budget become\nThe factors that limit daytime transpiration\ncomplicated for a frozen landscape, and\nalso restricted rates of carbon uptake by\nespecially so for seas with broken ice.\nthe forest.\nARL/ATDD has been engaged in two\nseparate research programs addressing\nThe ATDD Long-EZ experimental aircraft\nrelated issues, one funded by the NOAA\nconcentrated on measuring fluxes over the\nOffice of Global Programs and collaborative\nboreal forest near Candle Lake,\nwith NASA (\"BOREAS,\" in northern\nSaskatchewan during the second study\nSaskatchewan, Canada), and the other\nperiod. Aircraft flux measurements\nconducted with National Science\nprovided a measure of the spatial\nFoundation and Department of Energy\ndistribution and areal average of air-surface\nfunding and cooperative with San Diego\nexchange, and correlated well with the\nState University (on the Alaskan northern\ntemporal statistics from the tower\nslopes).\nmeasurements. The Long-EZ was one of\nfour airplanes measuring fluxes at this\nBOREAS 1994.\ntime. Its flight altitude was the lowest of\nthe four and it is expected to have sampled\nATDD provided continuous tower\nfluxes well within the region where surface\nmeasurements of heat, moisture, and CO2\nheterogeneity still has strong influence.\nfluxes from a 45 m tower in a\nThe forest was very patchy, with stands of\nSaskatchewan jack pine forest throughout\ntrees alternating with fens, barrens, cut\nthe whole growing season. However, most\nand burned areas, and lakes, all on\n1994 activity took place in three intensive\nkilometer scales or less.\nstudy periods - May/June, mid-July, and\nAugust/September.\nDuring the third period, heat, moisture, and\nCO2 flux data were once again collected\nA new global positioning system (GPS)\nfrom the tower, in and above a stand of old\nground station and software, purchased for\njack pine, and at 25 - 30 m above ground\nthe airborne flux system, was used for the\nusing the aircraft.\nfirst time in these intensive campaigns. It\nfunctioned exceptionally well; airplane\nThe ATDD Long-EZ was the only aircraft to\nposition error appeared to be within + 2 m;\nparticipate in all of the BOREAS field\nvelocity accuracy was about 0.03 m\ncampaigns. Early analyses of the airborne\ndata set are very encouraging. When\n13","AIR QUALITY AND DISPERSION\nviewed together with the tower data, it is\nThere were also several aircraft\nclear that there are substantial differences\nintercomparison runs, in which pairs of\nbetween the partitioning of energy of a\nflux-measuring airplanes flew in close\nboreal jack pine stand and that of a\nformation during the 1994 summer\ntemperate deciduous forest. Most of the\ncampaigns. The ATDD Long-EZ flew\nincident solar energy absorbed by the\nprimarily with the National Research\ntemperate forest is converted to latent\nCouncil (Canada) Twin Otter, although\nheat; most net radiation over the boreal\nsome runs were flown with the\njack pine stand becomes sensible heat.\nconsiderably faster University of Wyoming\n(On first principles, this is as must be\nKing Air. Comparison with the NCAR\nexpected, since the ratio of sensible to\nElectra was impossible because of the\nlatent heat flux is doubtlessly a strong\ndisparity of flight speeds.\nnegative function of temperature.) These\ndifferences in energy partitioning impact\nNorth Slope (Alaska) Flux Studies.\nthe rate of growth of the PBL.\nThis work focuses on the ways in which\nHuge differences in CO2 exchange rates\nnorth slope ecosystems serve as sources or\nwere also found. Greater uptake was\nsinks for a variety of air chemicals known\nobserved over the temperate forest,\nto affect global climate change, such as\nbecause its more benign climate and\ncarbon dioxide, methane, and most\ngreater nutrients and moisture availability\nimportantly water vapor. The work is\npermit more rapid photosynthesis.\ncollaborative with San Diego State\nUniversity; ARL is involved because of its\nA BOREAS Data Workshop in Williamsburg,\nunique capability to measure the rates of\nVA, 14-16 December, was the first\nexchange of carbon dioxide and water\nopportunity for BOREAS participants from\nbetween the air and the surface.\nall disciplines to present preliminary\nanalyses from summer 1994, and to\nFrom the local perspective, the work is\nconsider the emerging picture of carbon\ndesigned to provide information on how the\nexchange between the atmosphere and the\nground and the atmosphere interact, so\nBoreal Forest. Winter net CO flux is\nthat future industrial activities in the region\nupward, increasing in the spring until\ncan be organized and implemented to have\nleaves appear. Net daytime growing\nminimal adverse environmental\nseason exchange is only a small difference\nconsequences. From the global\nbetween photosynthesis and respiration, in\nperspective, the work is intended to refine\ncontrast to lower latitudes, where\nthe way in which the high-latitude\nphotosynthesis dominates. Latent heat\nterrestrial biosphere is described in models\nflux was unexpectedly low, relative to\nas a sink for atmospheric carbon dioxide.\nsensible heat flux, producing deeper mixed\nlayers and lower rainfall than models\nA preliminary study was conducted in\npredict.\n1993. San Diego State University\nconducted tower-based flux studies, and\nThe most notable feature of the aircraft\nthe ARL/ATDD Mobile Flux Platform (MFP)\ntransects was the repeatability of the\nprovided path-averaged airborne fluxes,\nmeasurements. Using averaging lengths as\nand an indication of their variability, using\nshort as one kilometer, the Bowen ratio\nthe Long-EZ test aircraft. In a subsequent\nwas virtually identical during three days in\nexperiment, in 1994, the Long-EZ also\nJuly, and agreed with tower-based flux\ncarried a downward-looking four-channel\nmeasurements. Figure 1 illustrates the\nradiometer. The four channels were set to\nheat flux data obtained.\nmimic satellite thematic mapper bands; it\n14","AIR QUALITY AND DISPERSION\nwas intended to use the data collected to\nsouth but still within the coastal flood\ncalibrate satellite techniques that use\nplain, mean ambient CO2 concentrations\nthematic imager observations. A high-\nwere found to increase sharply, presumably\nperformance video camera was also fitted,\nbecause of numerous oil-field flares. These\nto assist image-processing.\nflares complicated CO2 exchange rate\ncomputations, however, the data indicated\nThe aircraft flew along a north-south\nincreased CO2 uptake by the underlying\ntransect starting over the ocean and\nsurface, as would be expected along the\nextending to about 100 km inland.\nbiologically more productive coastal flood\nExceedingly complex meteorological and\nplain. Further inland, CO, 2 fluxes continued\nflux conditions were encountered. Over\nto indicate surface uptake, but not as\nthe ice-covered Arctic Ocean, the sensible\nrapidly as in the coastal regions. The\nand latent heat fluxes and CO2 flux were all\neffects of patchy clouds and numerous\nvery small. The influence of the ice\nlakes became apparent in the increased\nsurface on radiation and on the\nvariability of surface temperature and solar\ntemperature of the air and surface was\nradiation along the transect (from north to\nfound to be dramatic. Inland from the\nsouth). Although the sensible and latent\ncoast, the air was observed to warm\nheat fluxes were quite variable, they\nrapidly as more of the net radiation was\ncorrelated well with the available net\npartitioned into sensible and latent heat,\nradiation.\nrather than being stored in the soil. Further\nEnergy Fluxes - Candle Lake Transect\n1514-1822, July 23, 1994\n6 transects\n700\n5\n600\n4\n500\n3\n400\n2\nH\n300\nLE\nRn\nBowen Ratio\n1\n200\n0\n100\n-1\n0\nAspen\nAspen\nMixed\nCon\nLake\nCon\nL\nConifer-wet\n-100\n-2\n-106.4\n-106.2\n-106\n-105.8\n-105.6\n-105.4\n-105.2\n-105\n-104.8\n-104.6\nLongitude\nFigure 1. Heat fluxes (and Bowen ratio) from a BOREAS transect on July 23, 1994. From\nthe left, the distinct areas are Aspen forest, a small lake, Aspen, mixed forest, coniferous\nforest, a lake, coniferous forest, another lake, and more coniferous forest.\n15","","AIR QUALITY AND DISPERSION\nAIR-SURFACE EXCHANGE\nHeat, Momentum, Water, and CO2 Transfer at the Earth Surface\nBackground.\nBranch Watershed. The system\nis\nspecifically designed to provide\nARL conducts basic research on methods\nuninterrupted monitoring of momentum,\nfor predicting and measuring exchange of\nheat, water vapor, and carbon fluxes.\nmeteorological quantities (heat, moisture,\nand momentum) as well as of trace gases\nAt Research Triangle Park, and in\nand particles (e.g. ozone, carbon dioxide,\ncooperation with Oak Ridge, a separate\nsulfur and nitrogen oxides, base cations,\nportable flux-measuring system was\nnutrients, and radioactive and toxic\ndeveloped, this time designed for direct\nchemicals) between the atmosphere and\nmeasurement of trace gas fluxes. This\nvarious surfaces. The study of trace gas\nsystem is also described elsewhere (see\nand particle deposition is addressed\nAIRMoN-Dry). The system provides for\nelsewhere in this document (see \"AIRMoN-\ndirect eddy correlation measurements of\nDry\"). In general, however, the trace gas\nsulfur dioxide, ozone, and carbon dioxide\nand particle question is not limited to\nfluxes, and of nitric acid by filter pack\ndeposition, but also involves emission and\ngradient analysis, as well as the important\nresuspension.\ncomponents of the surface energy budget.\nThe system was tested in field programs at\nPresently, ARL focuses its attention on the\nBeaufort, NC, and at Bondville, IL.\ndevelopment of systems for measuring\nfluxes at specific locations, and the\nAlso at Research Triangle Park, planning\nextension of local measurements and\nstarted on a project to obtain a better\nunderstanding to describe areal average\nunderstanding of nitrogen oxide (NO)\nexchange in numerical models.\nemissions from soils (through a cooperative\nagreement with the NC State University).\nTower Studies.\nEstimates of these emissions are needed\nfor models like the Regional Oxidant Model\nTwo portable eddy flux systems have been\n(ROM) and the Regional Acid Deposition\ndeveloped, each providing a new tower\nModel (RADM). Nitric oxide emissions are\ncapability to monitor all eddy fluxes for\nthought to arise from microbial activity,\nwhich appropriate sensors are available. It\nwhich is enhanced when nitrogen-based\nis standard operating procedure to measure\nfertilizer is applied. A planning workshop\nroutinely the momentum, sensible and\nfor a pilot experiment was held in Raleigh\nlatent heat, and carbon dioxide fluxes in all\nduring March 1994. Representatives from\napplications of these new systems.\nNASA, Argonne National Laboratory,\nUniversity of Maryland, ARL-Oak Ridge,\nAt Oak Ridge, and as part of a continuing\nand ARL-Silver Spring participated. The\neffort to improve and streamline flux\nstudy was tentatively planned for May\nmeasurement systems, a tower-based eddy\n1995 on a farm in eastern North Carolina.\ncorrelation system powered by a 12 volt\nbattery with solar panel (and/or wind\nIn-Canopy Studies.\ngenerator) recharging was deployed in a\nlocal test program and subsequently\nDuring 1994, flux monitoring activities\ninstalled for extensive testing at the Walker\nexpanded at the Walker Branch Watershed\n17","AIR QUALITY AND DISPERSION\n(WBW) in Oak Ridge, with a new emphasis\nThe site was a farm, using mechanical\non distinguishing between the flux\nsystems to irrigate 800 m diameter circles.\ncontributions of the forest floor and the\nAnalysis of tower eddy correlation fluxes of\ntrees themselves. Two eddy-correlation\nheat and moisture continued through 1994.\nmeasurement systems continuously\nDifferences in the fluxes among alfalfa,\nmeasured energy and CO2 exchange both\ncorn, and wheat crops were found to be\nat the forest floor and above the canopy,\nsignificant. During daytime conditions,\nto evaluate the separate (ground and in-\ntranspiration rates differed by 20% to\ncanopy) sources of latent heat and CO2.\n50%.\nExperience gained in this effort will be\nimportant for anticipated surface-layer\nMeasurements of momentum, heat, and\nmodel testing and evaluation studies (under\nmoisture fluxes from the ATDD Long-EZ\nNOAA/GEWEX/GCIP). Computers at the\nresearch airplane were analyzed to quantify\nfield site are now linked in a network,\nspatial variabilities in the fluxes. Fluxes\nwhich will be used to retrieve data daily\nfrom an 800 m crop circle were compared\nfrom the flux systems and from standard\nto average fluxes from transects across the\nmeteorological arrays, to facilitate quality\nwhole farm. On average, a 50 to 100\nW/m² difference from field to field has been\ncontrol and data processing.\nfound during daytime hours. A similar\nThe Mobile Flux Platform, and GPS.\nassessment has been planned for the ARM\nSouthern Great Plains (Oklahoma) CART\nA major ARL development has been that of\nsite using modeled sensible and latent heat\nthe Mobile Flux Platform (MFP), a system\nfluxes. The model will be tested with\nthat corrects velocity records for the\nmeasurements recently obtained from the\neffects of using a sampling platform that is\nOklahoma site.\nnot rigidly fixed to the earth's surface.\nDuring 1994, the use of new Global\nCarbon Dioxide.\nPositioning System (GPS) technology was\nevaluated, and the newest available GPS\nContinuous eddy correlation measurement\nsystems were adopted. The MFP GPS\nof CO2 flux over the Walker Branch (Oak\nsystems were upgraded, and a\nRidge) forest continued through 1994,\npost-processing software from the\nalong with associated data analysis and\nUniversity of Calgary was implemented to\nmodel calculations. For the full year, the\nnet carbon exchange was 945 g m². This\nallow GPS Doppler velocities to be\ncorrected to + 2 cm/s (while flying on an\nis about three times the value measured by\naircraft at 50 m/s). Before this\nothers over the older and more northern\nmodification, platform velocity accuracy\nHarvard forest.\nwas limited to about I 20 cm/s. No other\nairborne systems are known that have a\nThe eddy flux measurement of CO2\nposition accuracy of I 3 m, angular\nexchange is now a mature technology.\naccuracy of I 1 milliradian, and velocity\nATDD organized (collaboratively with the\naccuracy of H 2 cm/s.\nUniversity of Tuscia, Italy) an international\nworkshop on Strategies for Monitoring CO2\nLarge-Area Exchange.\nFluxes over Terrestrial Ecosystems. The\nworkshop was conducted in December,\nThe Oak Ridge group deployed both tower\n1994, in Italy. The goal was to take a first\nand aircraft eddy correlation systems\nstep towards establishing a global network\nduring a 1971 study of areal fluxes over a\nthat can directly address the issue of the\nheterogenous but flat surface at Boardman,\n\"missing sink\" in the global carbon balance.\nOregon (as part of the DOE ARM program).\n18","AIR QUALITY AND DISPERSION\nTHE ATMOSPHERIC INTEGRATED RESEARCH MONITORING NETWORK\n(AIRMoN)\nA Research Monitoring Array for Early Detection and Deposition\nBackground.\nneeds with different protocols and (b) to\nprovide the detailed measurements\nThe Atmospheric Integrated Research\nnecessary to understand important\nMonitoring Network is an array of stations\nprocesses.\ndesigned specifically to detect the benefits\nof emissions controls mandated by the\nEarly Detection.\nClean Air Act Amendments of 1990, and\nto quantify these benefits in terms of\nThe specific goals of the AIRMoN rapid\ndeposition to sensitive areas. AIRMoN\ndetection monitoring program are\ncombines two previously-existing\ndeposition research networks that have\n- to provide regular, timely reports on the\nappropriate characteristics (previously\natmospheric environment consequences of\nknown as the MAP3S precipitation\nemission reductions, as imposed under the\nchemistry network and the CORE/satellite\nClean Air Act Amendments,\ndry deposition inferential method network)\nunder a single operational umbrella, so as\n- to extend these observations to wet and\nto provide a new monitoring activity to\ndry deposition rates that affect sensitive\nwhich on-line modeling and analysis can be\necosystems, and\neasily applied. An additional air-sampling\ncomponent of AIRMoN is anticipated, to\n- to provide a direct linkage between the\naugment the sampling already taking place\nmonitoring and modeling communities that\nunder the dry deposition activity and to\nare involved.\nprovide additional rapid-detection\ncapabilities.\nThe overall design target for AIRMoN is to\ndetect, with 95% confidence, the\nThe techniques of AIRMoN are specifically\natmospheric concentration and deposition\ndesigned to quantify the extent to which\nconsequences of a 5% reduction in\nchanges in emissions affect air quality and\nemissions, over a two-year period.\ndeposition at selected locations. A small\narray (about 20 to 30) such locations are\nAs currently planned, AIRMoN will be made\npresently intended for attention of this\nup of 20 to 30 measurement sites in total.\nkind. These locations will be chosen to\nThese sites will be arranged in three\noptimize the probability for detecting the\nsubnetworks. The wet deposition\nchange that is sought, and to serve related\ncomponent (AIRMoN-wet) already exists in\nneeds of effects researchers. Specific sites\npreliminary form, with 7 sites currently\nare (and will be) emphasized, where\noperating; eventually, it is planned to\noperations of different observing arrays can\ncontain about 20 sites. The dry deposition\nbe collocated. Such Collocated Operational\ncomponent (AIRMoN-dry) is planned to be\nResearch Establishments (\"CORE sites\")\nof similar size, although with as many as\nwill serve two additional distinct purposes:\npossible of its sites collocated with\n(a) to provide linkages among network\nAIRMoN-wet. There are presently 13 such\nprograms operating to address different\nsites.\n19","AIR QUALITY AND DISPERSION\nA smaller array of air chemistry\nTechnical Committee Meeting (October 24-\n27) final decisions were made regarding\nobservatories (approximately five such\nstations; AIRMoN-air) will provide the\nthe AIRMoN-wet quality assurance plan\nand site operator protocols. The basic\ndetailed chemical data required by some\nphilosophy remained unaffected by these\nspecific rapid detection techniques.\nnegotiations with other networks: report\nall of the data as fast as possible, give\nAIRMoN is intended to provide data needed\nby several alternative methodologies for\nthem to anyone who wants them in an\nelectronic format, and attach a simple\nproviding the rapid detection characteristics\nscreening code to allow the user to avoid\nthat are sought. These techniques are\ndescribed in detail in the following\nrelevant contamination problems.\nsummary; a combination of cluster analysis\nand prediction differencing methods will\nAIRMoN -- Dry.\nprobably be used.\nInterest, both national and international,\ncontinues in the NOAA Inferential Method,\nStatus.\ninitially developed under NAPAP auspices\nAIRMoN has been endorsed, in principle, by\nfor estimating dry deposition fluxes from\nsimple field measurements. Several foreign\nboth the National Acid Precipitation\nnetworks are contemplating adopting the\nAssessment Program (NAPAP) and NOAA.\nTo get started on the endeavor, the daily-\nAIRMoN approach, specifically South\nsampling precipitation chemistry research\nAfrica, Spain, and a number of central and\nprogram, previously operated under the\neastern European countries (as mentioned\nauspices of the Department of Energy was\nabove).\ntransferred to NOAA (the MAP3S\nImproved estimates of dry deposition rates\nprogram). Plans for AIRMoN were\nendorsed during 1992 by NOAA and by the\nfor AIRMON-dry sites were generated\nduring 1994. The network is arranged so\nDepartment of Commerce, and were\naccepted by OMB as an important\nthat flux estimates obtained throughout the\ncontribution to NAPAP and to the debate\nentire program can be periodically refined\nabout the consequences of the Clean Air\nas more is learned about the ways in which\nAct Amendments controls. The activity\nairborne pollutants are deposited.\nwas subsumed into a funding package now\nwell recognized - NOAA's \"Health of the\nExisting dry deposition algorithms for\ngaseous pollutants were examined, with\nAtmosphere\" initiative.\nprime attention to O3, SO2, and HNO.\nThe overall philosophies of the AIRMoN\nSensitivity tests showed that models were\nnetwork have been enthusiastically\nmost sensitive to land-use type and time of\nreceived elsewhere. In particular, a trial\nday. Accordingly, the data sets were\napplication of the general principles is now\nstratified based on these classifications for\nbeing planned for Central and Eastern\nuse in the future evaluations.\nEurope, where monitoring programs are\ncurrently in some disarray.\nAIRMoN -- Wet.\nField sampling continued without\ninterruption at the seven AIRMoN-wet daily\nsampling sites during 1994. At the\nNational Atmospheric Deposition Program\n20","AIR QUALITY AND DISPERSION\nAIRMoN-Wet\nA Nested Array of Daily and Weekly Sampling\nBackground.\nARL also operates a small array of weekly\nsampling sites, as a contribution to the\nThe longest U.S. network record of\nNADP. The accompanying figure shows\nprecipitation chemistry in the modern era is\nthe AIRMoN-Wet array.\nthat which started as the Department of\nEnergy's Multistate Atmospheric Power\nRoutine aspects of the AIRMoN program\nProduction Pollution Study (MAP3S) in\ncontinued throughout 1994. The AIRMoN\n1976. With the end of the acid deposition\nfield program continued uninterruptedly,\ndecade, and with the cessation of a formal\nwith samples collected on a routine daily\nresearch program under the National Acid\nbasis at all seven stations. Analysis by the\nPrecipitation Assessment Program, the\nsame central laboratory as services NADP\nMAP3S network was terminated by DOE\nis now routine. As many quality assurance\nand was eventually transferred to NOAA\nsteps as possible are shared between the\nwhere it remains a program of ARL,\ntwo arrays, but clearly the demand for\nconstituting one tier of the AIRMoN-Wet\nnitrogen species integrity imposes more\nprogram.\nstringent requirements on sample-handling\nfor AIRMoN, and the onorous collection\nThe major wet deposition network of the\nprotocols encourages rapid automation of\nU.S. is the National Atmospheric\nmany of the data gathering chores.\nDeposition Program (NADP), a large array\nof about 200 stations that collect weekly\nAIRMoN -- NADP Interactions.\nsamples of precipitation and have the\nchemical analysis performed at a single\nThe NADP sampling program is receptor-\ncentral laboratory. The weekly samples\noriented; it is based on requirements by\nhave two severe drawbacks: their\necologists, agriculturists, foresters, etc., to\nchemistry can be affected by biological\nquantify the input of chemicals from the\nactivity in samples that sit in the field for\natmosphere to potentially sensitive areas.\nseveral days before collection, and their\nFor such biologically-oriented purposes,\nweek-long averaging means that several\nweekly sampling is quite adequate. The\nrainfall events can be combined into a\ndaily sampling of AIRMoN, as required to\nsingle sample. Both of these drawbacks\nmeet the unique purposes of ARL, is\nare important considerations for NOAA.\nfrequently an item of some contention in\nThe first means that accurate quantification\nthe NADP community. During 1994,\nof ammonium and nitrate ion deposition is\nspecial effort was made to explain the ARL\nnot possible; the AIRMoN wet approach is\ninterests and data needs to the NADP\nto collect daily samples and to keep them\ncommunity. The effort was largely\nchilled so as to minimize biological activity\nsuccessful. A measure of the success is\nbetween collection and analysis. The\nthat AIRMoN-Wet is now accepted as a\nsecond complicates any interpretation or\nformal sub-program of NADP.\nanalysis that involves a coupling with\nmeteorology. In order to relate specific\nUse for \"Early Detection.\"\ndeposition events to specific source areas,\nsource-receptor calculations require daily\nThe requirement for daily sampling in order\n(or shorter) time resolution of the samples.\nto meet the demands of \"early detection\"\n21","AIR QUALITY AND DISPERSION\nwere illustrated. One was a matrix\nanalyses was also explained at the NADP\napproach showing all combinations of\nTechnical Committee meeting. An analysis\nsources contributing to all potential\nwas presented that shows a comparison of\nreceptors, while the second aggregated all\nsome of the methods proposed under the\nthe sources together, and in combination\nAIRMoN rapid detection program (see\nwith a chemical model, made actual\nseparate documentation here) to detect\npredictions of deposition at each sampling\ncleaner air due to mandated emissions\nreductions at selected locations before it is\nlocation.\nThese techniques, either\nindividually, or in combination, will be used\ndetectable by the larger array of weekly-\nto segregate the sampling data into smaller\nsampling stations. Examples were shown\nof receptor based methods, such as\nsubsets that have less variability.\ncomputation of back trajectories in\nDownward trends in these subsets should\nbe easier to confirm and attribute only to\ncombination with cluster analysis and\ngridded tabulations of trajectory\nthe reductions in emissions.\nfrequencies. Two source-based methods\nFigure 1. The AIRMoN-Wet array, showing both daily (solid) and weekly (open) sampling\nsites. The daily sites are the continuation of six sites of the MAP3S precipitation chemistry\nnetwork previously sponsored by the DOE, plus an additional site near Burlington, Vermont.\n22","AIR QUALITY AND DISPERSION\nAIRMoN-Dry\nNetwork Investigations of Dry Deposition\nBackground.\nOperational Research Establishments\n(\"CORE\" stations) of AIRMoN-Dry provide\nARL is a leader in the development and\na continuing infrastructure for exploratory\noperation of dry deposition networks.\nresearch. The much larger CASTNET array\nSince 1984, the Atmospheric Turbulence\nof the EPA is the routine network in which\nand Diffusion Division in Oak Ridge has\nthe results are applied. The tier of simpler\nbeen operating a network specifically\nstations of the NOAA AIRMoN-Dry array\ndesigned to get around the major problem\nserves as a transition, testing the\nconfronting dry deposition monitoring\ntransferability from the research\nactivities -- there is no existing method\nenvironment to routine application.\nsuitable for routine direct measurement.\nThe nested network that was developed\nThe Dry Deposition Inferential Method.\nconsisted of a small number of research\nsites supporting a larger array of stations\nInterest, both national and international,\nmaking simpler but more routine\ncontinues in the NOAA Inferential Method,\nobservations. The Dry Deposition\ninitially developed under NAPAP auspices\nInferential Method (DDIM) that was\nfor estimation of dry deposition fluxes.\ndeveloped remains the central routine\nRequests have been received for details of\nanalytical tool of the ongoing NOAA dry\nthe technique and for the latest version of\ndeposition trial network, now identified as\nthe inferential model for dry deposition\nthe dry deposition component of the\nvelocity from the U.S. Forest Service, from\nAtmospheric Integrated Research\na NOAA group designing a collaborative\nMonitoring Network (AIRMoN). This\nstudy of deposition in Central Europe, and\nnetwork started with six sites; thirteen\nfrom a South African electric utility.\nstations are now operating (as shown in\nthe accompanying figure).\nDuring 1994, a new multi-layered model\nwas adapted for dry deposition inferential\nThe Atmospheric Sciences Modeling\napplication, replacing the initial \"big leaf\nDivision in Research Triangle Park plays a\nmodel\" that had its origins in agricultural\ncentral role in the operation of the EPA\nmeteorology. The new model provides a\nClean Air Status and Trends Network\ngreatly improved capability to simulate the\n(CASTNET), which is the present-day\neffects of several natural variables known\ncontinuation of the EPA National Dry\nto be important in the dry deposition\nDeposition Network initiated under the\ncontext. However, some tests comparing\nNational Acid Precipitation Assessment\nthe two models indicated little\nProgram. The same inferential\nimprovement while the newer model was in\nmethodology mentioned above is the\nits early stages of development (for\nunderpinning of the CASTNET dry\nexample, results obtained in Europe as part\ndeposition program. The EPA and the\nof the EUROTRAC program).\nNOAA activities are wholly collaborative:\nboth operations are structured to apply\nResearch Activities.\nnew understanding as rapidly as possible,\nand to quantify the uncertainty associated\nThe major goal of dry deposition research\nwith the indirect (inferential) estimates that\nconducted under the AIRMoN-Dry program\nthe routine monitoring networks produce.\nrelates to the need to identify and\nIn simple concept, the Collocated\nunderstand the processes that cause dry\n23","AIR QUALITY AND DISPERSION\ndeposition, in order to quantify dry\nfirst test of this system was conducted\ndeposition rates at locations where direct\nnear Beaufort, NC. The system provides\ndirect eddy correlation measurements of\nmeasurement is not possible. ARL\nsulfur dioxide, ozone, and carbon dioxide\npresently focuses its attention on\nfluxes, and gradient measurement of nitric\nacid flux. The system also measures the\nthe development of systems for\nsurface energy budget. The system was\nquantifying dry deposition,\nsubsequently deployed at the Bondville\nCASTNET (and also AIRMoN and ISIS) site\nthe measurement of dry deposition\nin Illinois. Deployment at other sites will\nusing micrometeorological methods,\noccur during 1995. In essence, the flux\nthe development of techniques for\ndata obtained will be used to assess\nuncertainty and to improve the inferential\nassessing air-surface exchange in areas\ndry deposition models being widely used in\n(such as specific watersheds) where\nanalysis and modeling of dry deposition.\nintensive studies are not feasible, and\nThe ASMD team also conducted an\nthe extension of local measurements\nand understanding to describe areal\nevaluation of existing dry deposition\nalgorithms for gaseous pollutants to\naverage exchange in numerical models.\nidentify an algorithm for implementation\ninto the ISC-COMPDEP (Industrial Source\nImproved estimates of dry deposition rates\nComplex - COMPlex terrain DEPosition)\nfor sites in the NOAA AIRMON-Dry\nmodel. Model predictions were compared\nnetwork were generated.\nagainst O3, SO 2 and HNO 3 field data sets.\nSensitivity tests showed that the models\nTesting of DDIM Predictions.\nwere most sensitive to land-use type and\ntime of day (day/night), so the data sets\nThe ARL team at Research Triangle Park,\nworking with colleagues at Oak Ridge,\nwere stratified based on these\ndeveloped a movable system for direct\nclassifications for use in the evaluation.\nmeasurement of dry deposition fluxes. A\nFigure 1. The sites of AIRMoN-Dry, showing CORE (solid) and satellite (open) locations.\n24","AIR QUALITY AND DISPERSION\nAIRMoN & EARLY DETECTION\nDetecting the Benefits of Emissions Reductions\nBackground.\nconsidering dispersion, to define the\nupwind advection path from the\nThe Clean Air Act Amendments of 1990\nmeasurement point. (Note that dispersion\nimpose the need to monitor the benefits of\nis not reversible.) Cluster analysis is a\nthe mandated emissions reductions. At the\nfairly common method applied to data from\nsame time, a phased implementation of\na single station (single site sectorial\nnew controls is imposed, together with a\nsampling). This method is comparatively\nnew emissions trading approach that\nsimple and yields quick results. Cluster\ncomplicates the normal process of benefit\nanalysis is primarily a spatial analysis\nassessment through model development of\napplied to a given data set, receptor by\ndifferent scenarios. The Early Detection\nreceptor. To extend this approach to an\ncomponent of the NOAA Health of the\narray of stations, a gridded tabulation\nAtmosphere program is designed to detect\nmethod has been developed. Although\nthe benefits of emissions reductions rapidly\nmore applicable to a network situation, this\nenough to guide revisions of the Act or of\napproach is not readily applicable to time\nthe way in which it is interpreted.\nseries measurements.\nClassical monitoring programs are designed\n(b) Source orientation. The effects of\nto monitor the current status of key\ndispersion and atmospheric chemistry (non-\ncomponents of the environment, and to\nlinear as well as linear) can be taken into\ndetect trends in them. There is no inherent\naccount when the methodology targets\ncapability to relate observed changes to\nspecific sources, from which pollutants are\nany specific cause, possibly not associated\nassumed to be emitted. Source-receptor\nwith changes in emissions. In practice,\nmatrices can be developed, using\nobserved changes in concentration or in\ncalculations performed from all source\ndeposition may result from many causes.\nregions to all receptors. The technique\nTo detect those changes that can be\noffers considerable advantage: daily\nattributed to emissions reductions requires\nfractional contributions due to different\nnew methods for coupling monitoring with\nsources are computed, and detailed\nanalytical interpretative programs.\nchemical reactions are taken into account.\nHowever, the method involves\nVariations in air quality and deposition are\nmanagement of very large data files.\nprimarily due to meteorological, chemical,\nDifferences between predictions and\nand emissions factors, all varying on\nobservations can also form the basis for\ndiurnal, seasonal, annual, and decadal time\nanalysis. This prediction differencing\nscales. If the variance due to factors other\napproach can be used to compute trends in\nthan emissions reductions can be reduced,\nresiduals between measurements and\nthen the otherwise masked signal\ncalculations, from which the consequences\nattributable to the emissions changes\nof changes in emissions can be made more\nthemselves will be left more apparent.\nobvious. This method permits sequential\nreductions in the residual (unexplained)\nLagrangian Interpretative Methods.\nvariance, but does not easily associate a\nspecific receptor with a particular source.\n(a) Receptor orientation. Receptor-oriented\napproaches use trajectories, without\n25","AIR QUALITY AND DISPERSION\nthe simple matrix approach is that it is not\nReceptor Modeling.\nalways possible to combine sources linearly\nto obtain the total contribution at a\nEmissions from different sources carry\nreceptor. In that case it is necessary to run\nchemical signatures that can be used to\nthe full emissions with an iterative scheme\napportion observed pollution concentrations\naccounting for critical chemical reactions.\namong sources that have been\nappropriately \"fingerprinted.\"\nThe\nTrajectory clustering has also been\nspecialized receptor models that result rely\nevaluated. Grouping of trajectories into\non trace metals carried by particles to\ncommon spatial clusters is a method to\nidentify smelter emissions, carbon\nclassify different meteorological situations\nmonoxide to identify nearby automotive\nassociated with pollutant transport from\nsources, etc. In practice, sources of\ndifferent source regions. Deposition\nspecial interest are identified, and emission\nsamples collected at a selected AIRMoN\nsignatures are determined by source-\nsite for the entire year of 1993 were\nspecific sampling programs. Statistical\nexamined in relation to the number of\nmethods are then used to attribute as\ndifferent meteorological clusters that were\nmuch as is possible of the variance in\nidentified. For this initial data set, sample\nobserved concentration data to these\nduration was typically one day, but some\nsources. The method has the advantage of\nsamples represent longer periods. This\nbypassing the need for meteorological data.\nwould complicate the apportionment of\nIt has the disadvantage of requiring that all\nsamples among distinct meteorological\nof the chemicals of relevance are affected\nin the same way by all of the processes\nsituations.\ninvolved in transport and dispersion; this is\nPrediction differencing involves the\nespecially contentious when clouds are\nassumption of an appropriate emissions\npresent or when precipitation occurs.\ninventory; the model then calculates the\ndaily deposition amount by grid node over\nRecent Results.\nthe entire domain. Values are then\ninterpolated to individual AIRMoN sites.\nTests of the source-receptor matrix\nWhen applied to observations at a selected\napproach have resulted in the development\nAIRMoN site, the modeled distribution was\nof a specialized program for displaying the\nfound to compare favorably to the\ndistribution of normalized concentration or\nmeasurements. This enhances the\ndeposition from a selected source region\nconfidence with which the new Early\n(source orientation) or the contributions\nDetection program is being embraced.\nfrom source regions to a selected receptor\n(receptor orientation). This kind of display\nIn summary, tests conducted so far\ncan be used to determine which source\nindicate that there is profit in combining\nregions have the greatest impact on a\nthe techniques mentioned above, for\nreceptor. It should be noted that the\nexample by using cluster methods to\nhighest contributions will nearly always be\nidentify sites and days appropriate for\nfrom the nearest sources, so that a\nprediction differencing. The tests also\n\"receptor oriented\" map will look very\nindicate that improvements in the\nsimilar to a \"source-oriented\" map,\nprediction of precipitation will be required\nhowever the interpretation is quite\nto reduce variability even further.\ndifferent.\nTests of the matrix computational method\nhave also been conducted, using a similar\ncomputer simulation. One problem with\n26","AIR QUALITY AND DISPERSION\nCOASTAL ECOSYSTEM ATMOSPHERIC LOADINGS\nMeasuring the Input of Nitrogen to Sensitive Areas\nBackground.\nMonitoring Activities.\nARL has long-standing expertise in\nIn the past, monitoring of deposition in\nmeasuring the deposition of trace chemical\ncoastal areas has been largely avoided,\nconstituents of the atmosphere to sensitive\nbecause of the well-recognized difficulties\nareas, both by wet deposition and by dry.\nassociated with the influence of airborne\nRecent recognition that this atmospheric\nsea-salt. In a conscious attempt to learn\ndeposition can be an important contributor\nmore about how to measure coastal\nto eutrophication has elevated atmospheric\natmospheric deposition, ARL now operates\ndeposition to a new level of interest,\nseveral exploratory monitoring stations in\namplified by the realization that the\ncoastal areas. Techniques are being\natmospheric input is rarely taken into\ndeveloped to account for the roles of\naccount in the models currently used to\nterrain complexity in the models used to\nguide the policy process. Initial estimates\ninterpolate among monitoring sites and in\nfor the Chesapeake Bay indicate that about\nthe simulations used to assess likely inputs\n30% to 40% of the nitrogen loading is\nin the absence of field data. In particular,\nderived from the atmosphere.\ntechniques to account for moderate terrain\ncomplexity have been developed and are\nARL is currently developing methods for\nnow being included in assessment models.\nquantifying atmospheric deposition to\nAs yet, there has been no opportunity to\ncoastal ecosystems, with emphasis on\ntest the predictions of these models against\nnutrients and toxics. Current research is\nfield data, however steps to provide a\ndirected specifically to the roles of nitrates\nplatform suitable for collecting such data\nand airborne toxic chemicals. ARL is\nhave been initiated.\nfocussing initially on East Coast\necosystems - mainly the Chesapeake Bay\nStudies so far have concentrated on\nbut with some attention to the\nnitrogen compounds, these being key\nAlbermarle/PamlicoSound. State-of-the-art\ncontributors to the process leading to\nmodels are being developed by ARL\neutrophication. Most atmospheric nitrogen\n(Research Triangle Park), and advanced\ncompounds (excluding N2 and N20, which\nmeasurement systems are being deployed\nare inert in the lower atmosphere) fall into\nby ARL (Oak Ridge and Silver Spring).\ntwo categories: reactive nitrogen,\nsometimes referred to as oxides of nitrogen\nARL co-chairs the Chesapeake Bay Air\nor \"odd nitrogen,\" and reduced nitrogen\nQuality Coordination Group, an officially-\n(typically dominated by ammonia, NH3).\nendorsed body for consolidating and\nSome organic nitrogen species arise in the\ncoordinating activities among federal and\natmosphere from the interactions involving\nstate agencies. A highlight of this Group's\nnitrogen oxides and biogenic or\nactivities in 1994 was a specialist\nanthropogenic hydrocarbons, and are thus\nworkshop conducted at Mt. Washington,\ntypically referred to as a subset of reactive\nMaryland, to construct an ordered list of\nnitrogen.\nprojects designed specifically to reduce the\nuncertainty surrounding current estimates\nFor purposes of this discussion, the term\nof atmospheric deposition in coastal areas.\n\"organic nitrogen\" will refer exclusively to\n27","AIR QUALITY AND DISPERSION\nbiogenically derived nitrogen compounds\nterm, continuous monitoring. Thus, most\nsuch as amines and amino acids, and will\nspatial estimation of dry deposition has\nbe discussed separately.\nrelied heavily on a modeling approach (see\nthe accompanying summary). Even the\nThe relative abundances in air of the\ndetailed, site-specific models developed to\ndifferent forms of nitrogen - NO, NO,\ninfer dry deposition rates from on-site field\nHNO, particulate nitrate, NH3, organic\nobservations are limited in their ability.\nnitrogen - vary widely based on proximity\nComparative measurement/modeling\nto sources and on the prevailing conditions.\nstudies have shown that these models are\nHowever, current estimates indicate that\ninconsistent in their performance. The\nreactive nitrogen is the largest contributor\nreasons for the inadequacies are associated\nto atmospheric nitrogen loads to coastal\nwith surface characteristics (cuticular\nwaters (40% to 60%), with ammonia\nchemistry, leaf wetness, water stress, etc.)\n(20% to 40%) and organic nitrogen (O to\nthat are hard to quantify. These issues are\n40%)alsocontributing significant amounts.\nnot new, and they have been the subject of\nconsiderable debate. Although important\nWhen considering total atmospheric\nadvances have been made, a universally\ndeposition of nitrogen to a given\nacceptable spatial model is still far distant.\nwatershed, the largest uncertainties are\nassociated with the ability to estimate the\nOther Waterbodies.\nspatial distribution of dry deposition.\nBecause of its chaotic nature, wet\nThe relative contribution of atmospheric\ndeposition behaves ergotically wet\nnitrogen deposition to new nitrogen inputs\ndeposition at one site is much the same as\nto estuarine, coastal, and offshore waters\nat a neighboring site provided the averaging\naround the world ranges from less than\ntime is long enough. This fact allows\n10% up to 70%. Studies of other major\nmeaningful areal isopleth maps of wet\nEast Coast estuaries have provided\ndeposition and nitrogen chemistry to be\natmosphericnitrogenloadingestimates that\nconstructed. However, this is not the case\nrange between 18% and 39% of the total\nwith dry deposition. The mechanisms that\nnitrogen load. The uncertainties of these\ncontrol air-surface exchange are tied to\nstudies make it imperative to obtain a\nbiological and surface factors that are\nbetter understanding of the processes that\nhighly variable in space.\ntransport and deposit nitrogen to estuaries\nand coastal zones.\nEnough is known about the processes that\ncontrol dry deposition to permit a\nFuture Analyses.\nlandscape to be considered on a point-by-\npoint\nbasis.\nResults\nfrom\nsuch\nIn an effort to coordinate scientific\ninvestigations illustrate that time-averaging\nprograms to reduce existing uncertainties in\ndoes not smooth dry deposition patterns.\natmospheric loadings estimates, the\nIn fact, time-averaging helps reveal\nChesapeake Bay Program's Air Quality\ndifferences between neighboring locations.\nCoordination Group (with ARL as co-chair,\nThus, it is not possible to extract\nshared with the State of Maryland)\nmeaningful site-specific dry deposition data\nconducted a meeting of active scientists\nfrom large-area, time-averaged information\nfrom different contributing disciplines was\nwithout consideration of the site in\nconducted at Mt. Washington, Maryland,\nquestion. The problems with dry\non 29/30 June 1994. The challenge given\ndeposition are magnified by the fact that\nto the workshop was simple - to\nfor nitrogen species only an inferential\nconstruct a prioritized listing of practical\nmeasurement technique is suitable for long\nstudies that would make the greatest\n28","AIR QUALITY AND DISPERSION\nimpact on reducing the current uncertainty\nThe above top priorities reflect the\nin estimates of the contribution of\nrecognition that current models are likely to\natmospheric deposition to declining aquatic\nbe misleading, but that the extent of any\necosystem health.\nerrors cannot be judged because direct\nobservations of deposition are not yet\nThe listing that resulted is summarized\nmade.\nbelow (extracted from the CBP report\n\"Atmospheric Loadings to Coastal Areas:\n3 -- Improve biogeochemical watershed\nResolving Existing Uncertainties\"). It was\nmodels. The workshop recognized the\nconcluded that ongoing scientific\nimportant role of watershed chemical\ninvestigations are making considerable\nretention.\nprogress; in essence, any new efforts\nshould build on existing programs rather\n4 -- Improve emissions inventories and\nthan risk new starts that compete with\nprojections. Assessments of atmospheric\nthem.\ndeposition are necessarily at the mercy of\nemissions estimates; related estimates are\nThe emphasis of the workshop was on all\ncurrently highly imperfect.\nof nitrogen species, toxic chemicals, trace\nmetals, precipitation chemistry, airborne\n5 -- Extend the vertical and spatial\naerosols, and supporting meteorological\nmeteorological and chemical concentration\ninvestigation. In every one of these cases,\ncoverage. Assessment models of today\nthe general call for a new focus applies,\nneed more advanced input data than the\nalthough with different weights according\nsimpler models used in early assessments.\nto the particular emphasis. The following\nAs the new models evolve further, input\nprioritized list was developed.\ndata requirements will increase even\nfurther.\n1 -- Conduct intensive, coordinated\nintegrated monitoring at special locations\n6 -- Implement an extensive array of less\nwithin the watershed, with wet deposition,\nintensive measurements. This item follows\ndry deposition, and local catchment area\non from Priority 1. In essence, a nested\ncharacterizations. It was concluded that\nnetwork is envisioned, with a small number\nthe single most limiting factor in assessing\nof intensive stations supporting a denser\nthe adequacy of current models is the lack\narray of simple stations designed to provide\nof high quality data on actual deposition\nimproved spatial resolution for some\nwithin the target watershed.\nselected variables.\n2 -- Work to improve existing atmospheric\nmodels. In brief, there are many limitations\nof current models, especially including their\nlimited grid size (smaller grid cells are\ndesired) and their inability to handle\nimportant orographic and chemical factors.\n29","","AIR QUALITY AND DISPERSION\nNITROGEN DEPOSITION TO THE CHESAPEAKE BAY\nIdentifying the Airshed using RADM\nBackground.\nof NO emissions to the atmosphere will\nhave the greatest benefit on reducing the\nEutrophication of Chesapeake Bay has led\nnitrogen loading to coastal estuaries.\nto anoxia at the bottom and major loss of\nSome NOx controls are anticipated through\nbiological productivity. Eutrophication is\nrequirements in the 1990 Clean Air Act\ndriven by both phosphorous, P, and\nAmendments.\nNitrogen, N. However, for the main Bay\nand the deep trench (the saline portions of\nThis work is important to the success of\nthe Bay), water quality models and data\nthe Chesapeake Bay Program Office's\nanalyses indicate that reduction in nitrogen\nefforts to achieve a 40% reduction in\nloading is the best way to reduce anoxia.\ncontrollable nitrogen loading to the Bay by\nThus, nitrogen is the driving pollutant for\nthe year 2000 and to the Program's\neutrophication in Chesapeake Bay.\ndeliberations regarding the 1992 renewal of\nthe Bay Agreement.\nNitrogen input from the atmosphere\nrepresents a significant source of nitrogen\nDevelopment of more accurate spatial\nto the Bay (25-35%) of the nitrogen\nfields of nitrogen loading estimates involves\nloading. Control of nitrogen oxide air\nestimation of annual average nitrogen\nemissions should be beneficial for air\ndeposition to coastal areas. The model \"of\n(oxidants), aquatic (acid deposition), and\nchoice\" is the Regional Acid Deposition\nestuarine (eutrophication) systems. Water\nModel. Deposition estimates are made\nquality models have incorporated\nstarting with the new 1990 interim\natmospheric nitrogen, but in a very simple\nemissions inventory and representative\nmeteorology.\nmanner.\nEstimating N Deposition.\nDefinition of the Airshed.\nA major objective of the RADM modeling\nAn understanding of the airshed influencing\nactivity is to improve current estimates of\nthe Chesapeake Bay watershed has\nnitrogen loading from the atmosphere to\nemerged from using RADM as a laboratory\nthe Chesapeake Bay watershed and the\nof the real world; sensitivity studies have\nBay itself. These estimates will be\nbeen conducted that elucidate the\nprovided as inputs to the water quality\ncontributions of different emissions sources\nmodels for the watershed (the HSPF model\nto the Bay watershed. This source-\nadapted by the Chesapeake Bay Program\nreceptor understanding is very difficult\nOffice) and the Bay (the 3-D Bay Water\n(nearly impossible) to develop from\nQuality model developed by the Army\nempirical data and requires the designing of\nCorps of Engineers).\nsensitivity studies to extract the relevant\ninformation from a mathematical model.\nAnother objective is to determine the\nairshed that is primarily responsible for the\nRefined Deposition Maps.\natmospheric nitrogen affecting the Bay\nwatershed. The airshed will be larger than\nTo improve the linkages between the\nthe watershed. The overall purpose is to\natmosphere and the Bay watershed (and\ndevelop an understanding of which controls\nthe Bay itself), a new higher resolution\n31","AIR QUALITY AND DISPERSION\nRADM with 20-km grids, nested within the\nThese relate to estimating the reductions in\noriginal 80-km domain, was developed.\ndeposition that are expected to occur due\nThe aggregation technique used to develop\nto the 1990 Clean Air Act and to\nannual average deposition was adapted for\nimplementation of new reductions in NOx\nthe 20-km domain. The 20-km domain\nemissions due to requirements stemming\nnested in the 80-km domain is shown in\nfrom oxidants, rather than acid rain. This\nFigure 1. Higher resolution is needed to\nwork is under way.\nresolve urban and major point source\ninfluences better, and to reveal local and\nThe Chesapeake Bay Airshed.\nregional-scale gradients. More attention\nalso needs to be given to subgrid\nIdentification of an \"airshed\" first requires\nphotochemistry affecting nitric acid\nan assessment of the responsibility of\nproduction, and to dry deposition to water\nemissions sources, as influenced by annual\nsurfaces.\nmeteorology.\nThe nitrogen deposition at any one receptor\narea derives from a large number of\nsources, spread out over a large geographic\nAn assessment of source\narea.\nresponsibility or a range of influence cannot\nbe constructed, therefore, from monitoring\ndata. A range was determined with the\nRADM model through development of an\noperational procedure for \"tagging\" the\nNOx emissions regions. Then it was\nnecessary to develop a measure that\nnormalizes for different rates of emissions.\nDifferent emissions rates influence the\nabsolute deposition and, of course, the\nfraction of the total deposition contributed\nby a source region. A measure for\nidentification of the airshed needs to be\ninsensitive to emissions rates. A relative\nmeasure, based on the total deposition due\nto the \"tagged\" source summed across the\nentire modeling domain was developed.\nFigure 1. The computational domain of\nUsing this approach, it was determined that\nRADM, showing the smaller 20-km grid\nwithin the original 80-km grid domain.\n50% of the nitrogen deposition to the\nBay itself is from sources 150 to 300/350\nThe more resolved representations should\nkm distant, and\nprovide an improved linkage with water\nquality models. However, the increase in\n75% of the nitrogen deposition to the\nspatial resolution quadruples the cpu\nBay is from sources 250/300 to 600/800\nrequirements for each study.\nkm distant.\nAs a first step, the new high-resolution\nIn each case, the larger distance estimates\nRADM is being used in two major\nrepresent the distance in the prevailing\ninvestigations addressing needs identified\nwind direction. These ranges clearly show\nby the Chesapeake Bay Program Office.\nnitrogen deposition is a regional problem.\n32","AIR QUALITY AND DISPERSION\nA comparison of the nitrogen \"tagged\"\nairshed is roughly 900,000 km 2 more than\nsub-regions with the tagged sulfur model\n5.5 times the watershed's 165,000 kmi\nfor the exact same sub-region indicated the\nThese results are very important and\nrange of influence of NO emissions is very\neffectively have set the stage for FY 95\nsimilar to the range for NOx. This is not\nwork, as intended.\nwhat was expected, producing a surprise.\nThis result will need to be investigated\nfurther. These ranges translate into\nWATERSHED AND EXPANDED AIRSHED OUTLINES\natmospheric residence times on the order\nof 1 to 1.5 days. These residence times\nfor sulfur are shorter than older literature\nestimates but in line with newer estimates\nthat take clouds and aqueous chemistry\ninto account.\nThe comparability of the SO2 and NOx\nranges of influence allowed us to use both\nsulfur and nitrogen \"tagged\" results to\nmore precisely estimate or define the\nairshed affecting the Bay watershed. The\ngoal in the identification of the principal\nairshed was to identify the source regions\nLEGEND\nWatershed\ncontributing the majority of the deposition\nAirshed\nto the watershed and to define the\nperimeter of diminishing returns. That is,\nthe perimeter beyond which it would not\nbe cost effective to reduce emissions from\nthe perspective of reducing nitrogen\ndeposition to the Bay watershed. A\ndecision rule was developed to assess the\nFigure 2.\nThe watershed and the\npoint of diminishing return. A reasonable\n(considerably larger) airshed of the\napproximation was the isocontour defining\nChesapeake Bay.\nthe distance at which 60% of the\ndeposition from a source regions had fallen.\nUsing this decision rule, source regions\nwere examined, moving counter-clockwise\naround the boundary of the watershed and\nthe decision rule used to define those\nregions to be included in the airshed.\nSuch a procedure produced a definition of\nthe airshed affecting the Chesapeake Bay\nwatershed that is evident in Figure 2; the\nairshed is significantly larger than the\nwatershed. The airshed includes many\nsources along the middle and upper Ohio\nRiver and it was surprising how far down\nthe Ohio River, to around Lexington, KY,\nutility sources are apparently influencing\nthe Chesapeake Bay watershed. The\n33","","AIR QUALITY AND DISPERSION\nMODELS-3\nA Third Generation Air Quality Model\nBackground.\nAtmospheric processes are treated as\ninterchangeable science modules to enable\nA flexible environmental modeling and\nrapid testing and integration of new\ndecision support system, called Models-3,\nscience. These modules contain explicit\nis being developed to provide air quality\nformulations of scale and coordinate\nassessment and decision support tools for\ndependencies. To achieve acceptable\nuse direct by Federal, State, and industrial\nturnaround for its users, the system\norganizations engaged in a wide variety of\nincorporates high performance computing\nenvironmental research and applications.\nand communications technology. For\nModels-3 is a project of ARL/ASMD at\nexample, key algorithms are being adapted\nResearch Triangle Park. It is a joint\nto take advantage of parallel computing.\nprogram with the EPA to integrate not only\ntraditional air quality modules but also the\nAn environment layer contains a number of\ndata preprocessing and postprocessing\nsystem \"personalities\" (e.g. Unix, MS\nsteps into a complete and efficient\nWindows, etc.) that adapt Models-3 to the\nsimulation system.\nparticular platform, system software, and\nplatform dependent files available. Data\nThe Models-3 Framework.\naccess is through a standard Input/Output\nApplications Programming Interface.\nThe initial development effort is focused on\nNumerous rapid prototypes have been\nmulti-scale, multi-pollutant air quality\ndeveloped to test the feasibility of various\nmodeling related to ozone non-attainment,\ncomponents of the system. Testable\nacid deposition, and fine particles.\nsystems requirements have been prepared\nHowever since many of the fundamental\nfrom interviews with potential users and\ntechnology and science issues being\nknowledge gained through early\naddressed are directly applicable to other\nprototypes. An early prototype which\nenvironmental modeling domains, the long\nsimplified the data preparation, execution,\nterm goal is to extend the system to handle\nand data analysis of the Urban Airshed\nintegrated cross-media assessments and to\nModel has been released to several groups\nserve as a platform for community\nfor initial testing and feedback.\ndevelopment of complex environmental\nmodels. The modeling framework is\nThe initial version of Models-3 is provides\ndesigned to automate many of the\nstate-of-the-art urban and regional ozone,\nactivities associated with air quality model\nacid deposition, and aerosol modeling, with\ndevelopment, evaluation, and execution.\nuser-friendly human-computer interaction\nThe framework design isolates system\nand automated management of processing,\ninterfaces and specific hardware/software\ndata, and resources.\nplatform solutions to ensure that advances\nin technology can be integrated without\nThe HPCC Linkage.\nmajor revision to the structure of the\nsystem. Graphical user interfaces provide\nModels-3 is closely associated with the\nease of use for major functions, such as\nHigh Performance Computing and\nplanning and executing a study, managing\nCommunications program (HPCC). This\ndata, or building a new model.\nprogram is part of a larger multiagency\nFederal High Performance Computing and\n35","AIR QUALITY AND DISPERSION\nCommunications program sanctioned under\nProjection (GEMAP) system. Primarily\nthe \"High Performance Computing Act of\nbecause of its design and GIS capability,\n1991\" and coordinated through the\nthe decision was made to use GEMAP as\nCommittee on Information and\nthe basis for Models-3 emission\nCommunications of the National Science\nprocessing.\nand Technology Council. The major\nprogram goals are: 1) to build advanced\nParallel Algorithm Research.\ncapabilities to address multipollutant and\nmultimedia issues; 2) to adapt\nA highly vectorized version of the\nenvironmental management tools to high\nquasi-steady state approximation (QSSA)\nperformance computing and\ngas-phase chemistry solver was developed\ncommunications; and 3) to provide a\nand implemented for the Models-3\nmodeling and decision support environment\nprototype. This solver makes minimal\nthat is easy to use and responsive to\nassumptions about the type of mechanism\nenvironmental problem solving needs of\nemployed and is intended to be used as a\nkey State, Federal, and industrial users.\nbasic algorithm for the development of\ngeneral gas-phase chemical mechanisms in\nThe 1994 Workshop.\nModels-3. In addition, a simplified testbed\nmodel was developed, to provide an initial,\nTo help finalize design of Models-3 science\nrepresentative chemistry-transport model\ncomponents, a second Models-3 science\nas a solver development and testing\nworkshop was held in September 1994.\nenvironment for distributed and massively\nThe second workshop was intended to\nparallel computing architectures. The\ndiscuss science deficiencies identified\ntestbed has been implemented on a Cray\nduring the first workshop. About 50\nT3D massively parallel processing system\nscientists developed detailed tasks needed\nin both the Parallel Virtual Machine (PVM)\nfor the completion of the Models-3 Initial\nprogramming model and the Cray Research\nOperational Version (IOV). Key research\nAdaptive ForTran (CRAFT) model.\nareas that were identified are: soil\nmoisture, resistance, and subgrid landuse;\nFuture Objectives.\ncloud process and aqueous chemistry;\nhydrostatic and nonhydrostatic modeling\nThe detailed design specifications for the\nissues for National Weather Service and\nModels-3 framework will be finalized,\nchemistry-transport models; emissions\ncoded and tested. Tests will also be\nmodeling; generalized coordinates and\nperformed to analyze communications\nmeeting technique; plume-in-grid modeling;\nissues between coupled meteorology and\ngas-phase chemistry reader and solver;\nair quality models. Numerous tests will\nhorizontal diffusion; aerosol modeling;\nexplore the advantages and limitations of\nactinic flux and radiation; and observation\ndistributed computing in a hardware\ndatabase for model evaluation.\nenvironment that employs both vector and\nparallel processing components. Models-3\nEmission Data Processing.\nvisualization prototypes will be tested to\nevaluate latency effects in a network\nThere are three primary options for an\nparallel environment where functional\nModels-3 emission inventory processor, (1)\nmodules are executed on distinct systems\nthe existing Flexible Regional Emissions\nto support animation, image rendering and\nData System (FREDS), (2) the Emission\nimage display. Remote collaborative\nProcessing System (EPS) associated with\ncomputing approaches will be evaluated for\nthe Urban Area Model, and (3) the\neffectiveness.\nGeocoded Emission Modeling and\n36","AIR QUALITY AND DISPERSION\nOZONE RESEARCH IN ARL\nStudies of Ozone, and NARSTO\nBackground.\nwith the conclusions drawn from chemical\nprocess studies conducted mainly by other\nTropospheric ozone has continued to be a\nlaboratories, are ingested into the\nproblem in the continental U.S. and\ncomprehensive models such as are being\nsoutheastern Canada despite decades of air\ndeveloped in the Atmospheric Sciences\nquality regulation and several generations\nModeling Division, Research Triangle Park.\nof legislation. The general problem was\naddressed in the recent NSF report\nSeveral of the most relevant ARL activities\nRethinking the Ozone problem in Urban and\nare discussed below. These relate\nto\nRegional Air Pollution; this called for a\nsurface deposition, tropospheric ozone\ncoordinated multi-agency approach to\ntransport, and chemistry (including tracer\nozone research. The North American\ntechnologies).\nResearch Strategy for Tropospheric Ozone\n(NARSTO) resulted from these beginnings.\nSurface Ozone Research.\nSponsors of the program include NOAA,\nEPA, DOE, EPRI, the American Petroleum\nWork on ozone deposition is ongoing at the\nInstitute, the Motor Vehicle Manufacturers\nAtmospheric Turbulence and Diffusion\nAssociation, and many power companies.\nDivision, in Oak Ridge, Tennessee, and at\nthe Atmospheric Sciences Modeling\nThe goal of NARSTO is to carry out a\nDivision, Research Triangle Park, North\nresearch program which will provide data\nCarolina. Much of what is known about\nfor the development and evaluation of air\nthe destruction of ozone upon contact with\nquality control strategies. This relates well\nthe surface (\"air-surface exchange\" of\nwith the dominant goal of ARL research.\nozone) has been the result of intensive field\nEffective action to control ozone levels can\nstudies made at locations that are carefully\nonly be taken if the mechanisms of ozone\nselected to permit scrutiny of particular\nproduction and transport are understood\nprocesses without confusion from\nand if the effects of control measures on\ncompeting mechanisms.\nozone levels can be measured. Reliable Air\nQuality Simulation Models (AQSMs) must\nIt is studies of this kind that have\nbe developed and tested so that the effects\ngenerated the knowledge that is currently\nof control strategies can be predicted.\nintegrated into numerical models of the air-\nsurface chemical exchange mechanism.\nARL has many relevant strengths, some of\nThese models emphasize that the\nwhich are described elsewhere in this\ncontrolling property is often biological,\ndocument (e.g. the Twin Otter flux-\nassociated with the stomatal resistance of\nmeasuring aircraft). ARL focuses research\nthe vegetation at the surface and hence\nattention on improving understanding of\nstrongly a function of the biological species\nthe processes that influence the\nand the prevailing conditions. Recently,\ngeochemical cycles of ozone and its co-\nARL has been moving more towards long-\npollutants. ARL research concentrates on\nterm measurement programs of similar\nthe physical (and frequently biological)\nkind, to capture a wide range of\nmechanisms that influence ozone\nenvironmental conditions at a single\nconcentrations. Results obtained, together\nlocation. This approach is useful, for\n37","AIR QUALITY AND DISPERSION\nexample, to evaluate model performance\nchemiluminescence) and perhaps\nduring conditions of short-term water\nexploration of sensitive, fast-response\nmeasurements of biogenic hydrocarbon\nstress, dewfall, precipitation, etc.\nprecursors (isoprene, etc.) to quantify\nMeasurement capabilities include flux-\nemission/deposition fluxes of these\nmeasuring systems for use on towers as\ncompounds to/from the atmosphere. Much\nwell as aircraft and boats. In general,\nof this work is in collaboration with the\nmeasurements at fixed locations are used\nDepartment of Meteorology, University of\nto investigate temporal variations in fluxes\nMaryland.\nand in the process that control them.\nAircraft and boat measurements have\nTropospheric Ozone Research.\nrecently been made possible by the\ndevelopment of a Mobile Flux Platform\nThere has been a long history of boundary\ncapability, that can now be used to\nlayer research within ARL, in which studies\ninvestigate the spatial distribution of fluxes.\nof ozone profiles have been common. For\nIn association with the development of this\nexample, ARL scientists have routinely\nmulti-faceted flux measuring capability,\noperated a tethersonde system to obtain\nnew fast-response ozone sensors have\ninformation of this kind, often supported by\nbeen developed. Further improvements are\nprofile data derived from use of aircraft.\nbeing made at this time, to provide more\nstable and sensitive response from the\nSeveral extensive field studies have been\ninstrumentation.\nconducted. These include the Lake\nMichigan Ozone Study, the San Joaquin\nThe models developed in this work are\nOzone Study, and the Arizona Ozone\nused routinely to assess ozone air-surface\nStudy. In each case, the focus was on the\nexchange at many sites distributed across\ncauses of ozone anomalies of potential\nthe U.S., with most in the East. The\nregulatory concern.\nmonitoring of ozone concentrations remains\ncentral to this network operation. Data\nThe performance of ozone monitors used in\nobtained are used not only to address\ntropospheric boundary layer research was\nresearch questions related to surface\na major worry during the early 1990s. The\nchemical and biological processes, but also\nresults of this research are now widely\nto determine ozone exposure levels within\nknown, and the studies themselves have\necosystems, ozone uptake rates by\nbeen finalized.\nvegetation, and human health risk.\nA central interest at the time of this writing\nCurrent work is directed towards exploring\nrelates to how gas-phase photochemical\nthe complex and rapid interactions among\nreactions and processes interact with the\nvarious nitrogen oxides, hydrocarbons, and\nmeteorological processes that cause\nozone in the near vicinity of vegetated\ntransport and dispersion.\nCritical\nsurfaces, where the reactions cause fluxes\nmeasurements in this effort include O3,\nto change with height much more rapidly\nNO/NO/NO,, H2O2 and ROOH (organic\nthan for non-reactive species. Work of this\nhydroperoxides), CO, etc. An effort in re-\nkind requires the use of rapid-response\nestablishing and enhancing ARL\nsensors, presently still under development.\nmeasurement capabilities involves the\nAttention will first be paid to developing a\ndevelopment of ultra-sensitive and fast\nfast-response NO detector, additional\nresponse detectors for reactive nitrogen,\nmethodologies for fast-response\nincluding the building and testing of a\nmeasurements of O3 (i.e., reverse NO\nsuper-sensitive and fast-response NO\nchemiluminescence and/or ethylene\ndetector, and the appropriate converters for\n38","AIR QUALITY AND DISPERSION\nthe detection of NO (photolysis cell) and\nozone measurements made at the same\nNO (molybdenum and/or Au/CO oxidation).\ntime as studies of meteorology. This long-\nSeveral ARL divisions (notably at Silver\nstanding work has recently been expanded\nSpring, Research Triangle Park, Oak Ridge,\nby a new focus on effects due to\nand Idaho Falls) are well equipped to\nvegetation differences.\nTogether,\nmeasure ozone; effort is now being\ntopographic and vegetation differences are\ndirected towards measurement of ozone\nreferred to in the general class of \"land\nprecursors.\nuse.\"\nAn understanding of the effects of\nARL specializes in measurements of\nmeteorological variables on tropospheric\ndeposition from the atmosphere, using all\nozone levels is essential to the detection of\nof micrometeorological tower-based,\nair quality changes resulting from emissions\naircraft, and inferential methodologies. ARL\nreductions. Only when these effects are\nscientists (especially at Research Triangle\nknown can air quality data be normalized\nPark) are active in studies of exchange\nfor meteorology and changes detected.\nbetween the boundary layer and the free\nThe effects of humidity, temperature,\ntroposphere, including the transport of\nclouds, and solar radiation on ozone\nozone and precursors by convection in\nproduction must be measured.\nclouds and the interactions at the marine-\nDetermination of diurnal and seasonal\ncontinental boundary layer interface. ARL\nvariations in meteorological parameters and\nis the lead agency of the World\nthe changes in ozone production and\nMeteorological Organization's Quality\ntransport they produce are necessary. The\nAssurance Center for the Americas, a\nchanges caused by climate patterns and\ncornerstone activity of the WMO Global\nresulting from solar radiation changes\nAtmosphere Watch with specific concern\ninduced by stratospheric ozone depletion\nrelated to the measurement of tropospheric\nshould be investigated. This\nozone.\nmeteorological data must have sufficient\nspatial and temporal resolution to enable\nboundary layer characterization including\ninversion height changes.\nThe fact that the transport of ozone and its\nprecursors affects ozone levels in urban\nareas is well known. Violations of National\nAmbient Air Quality Standards (NAAQS)\nmost often occur when new photochemical\nproduction is added to a high background\nozone level. The origin of the high\nbackground ozone and the effect of\ntransport on rural ozone, particularly the\ntransport of reservoir species such as PAN,\nmust be clarified. The entire range of\nspatial and temporal scales must be\nconsidered from flux measurements at the\nsurface to regional concentration gradients\nin both the horizontal and vertical\ndimensions. In this context, ARL has long\nbeen a leader in studies of flow and\ndispersion over complex terrain, often with\n39","","CLIMATE TRENDS AND VARIABILITY\nAEROSOL STUDIES\nAtmospheric Aerosols and Climate\nBackground.\nwas undertaken, using hemispheric and\nglobal surface temperature (IPCC90)\nIt is widely acknowledged that atmospheric\nrecords. Linear regression of five year\naerosols influence climate in a manner that\naverage temperatures (1960-1990) on CO2\ntends to counter the more familiar\nconcentrations (from Mauna Loa) yielded\ngreenhouse effect -- the increases in\ntemperature increases corresponding to a\nsurface temperatures resulting from\ndoubling of the current CO2 level of 2.3° +\nincreases in atmospheric carbon dioxide\n0.8° and 2.5° I 0.6° for the northern and\nwill be reduced if atmospheric aerosols also\nsouthern hemispheres respectively. No\nincrease in concentration. ARL workers are\nsignificant correlation was found between\ninvolved in several related activities.\nthe same temperature record and SO2 data\nas published by the IPCC.\nSoil-derived Particles.\nThe radiation effect of aerosol water in the\nInvestigations of the resuspension of\nmarine boundary layer (MBL) was\nsurface particles are summarized elsewhere\ninvestigated independently using the\n(see \"Erosion, and Resuspension of Aerosol\naerosol data measured during the 1992\nParticles\"). Studies of the optical\nASTEX/MAGE intensive. Based on the\nproperties of soil derived aerosols show\nshipboard measurement data of \"ambient\"\nrelatively unchanging size distributions and\nand \"dry\" size distributions it was\nreal and imaginary parts of the index of\nestimated that aerosol water would\nrefraction for soil-derived aerosols ranging\nincrease the aerosol optical depth of the\nfrom the Sahara to Texas to Central Asia.\nmarine boundary layer by 41% to 110%,\nConcentrations of soil-derived aerosols vary\nwhich corresponded to 0.6% to 1.4%\ngreatly in time and location, however. It is\ndecrease in the total solar irradiance at the\nproposed that these rather uniform aerosol\nsurface.\ncharacteristics and the extremely variable\nconcentration of soil-derived aerosols make\nA further activity relates to the\nthe most cost-effective studies on the\ndevelopment and optimal use of various\nforcing of climate by soil aerosols to be\nkinds of rotating shadow band radiometers.\nquantification of the change of soil aerosols\nThere are three variations now in use, each\nwith time.\nwith a specific purpose but each also\nemploying an identical measurement\nPresent studies concentrate on revealing\nphilosophy - as much as possible to\nthe aerodynamics of soil particle emissions.\ndepend on the use of a single sensor to\nThe two main study areas are Owens (dry)\nmeasure different irradiance components,\nLake in California and the Jornada del\nto minimize difficulties caused by sensor\nMuerto experimental range in New Mexico.\ndeterioration and to minimize the\nconsequences of different sensor\nAnthropogenic Particles.\nperformance characteristics when operating\nin a spatial array.\nAn attempt to use existing records to\nquantify the climate forcing of potential\nSome practical applications of atmospheric\ncloudiness generated by SO2 emissions\nextinction data do not require exceedingly\n41","CLIMATE TRENDS AND VARIABILITY\nhigh accuracy but rather continuing long-\nterm precision. Relative measurements\nthat encapsulate changes in scattering\nconditions can be made at small cost but\nwith lasting benefit. Such measurements\ninclude monitoring the relative magnitude\nof the direct and diffuse irradiance\ncomponents in an optically active portion\nof the solar spectrum. A single sensor that\nis periodically shaded by a rotating shadow\nband provides adequate data for many\npurposes of this kind. The simplest form\nof rotating shadow band radiometer is of\nthis type. A single, silicon-cell, quantum\nsensor is mounted horizontally at the\ncenter of the sphere described by a rotating\nband, thick enough to provide a short\nperiod of shade but narrow enough to\nminimize errors in the measurement of total\nirradiance. Broad-band data are collected\nautomatically, usually at intervals short\nenough to ensure that a representative\nfully-shaded value is reported for each brief\npass of the shadow-band. Such sensors\nare being operated by ARL at numerous\nsites.\n42","CLIMATE TRENDS AND VARIABILITY\nEROSION, AND RESUSPENSION OF SURFACE PARTICLES\nMechanistic Studies\nIntroduction.\nLas Cruces, NM. During 1994,\nthe\nresearch focus was on experimentation at\nThe desertification and resuspension\nOwens Lake.\nproject is a field component of the Fluid\nModeling Facility of the Atmospheric\nARL Resuspension Research.\nSciences Modeling Division, at Research\nTriangle Park. The project concentrates on\nThere is a well known \"wind erosion fetch\nthe mechanisms of resuspension and their\neffect\" that refers to the increase of\ndescription in numerical simulations. On a\nerosion rate with distance downwind from\nglobal scale the effect of these\na leading edge, after the threshold velocity\nmechanisms furnishes signals of global\nfor wind erosion is exceeded. Two new\nchange. For example, ice core researchers\nmechanisms for this fetch effect have been\nhave found a strong correlation of dust\nproposed. The first involves an\nconcentration in the ice and Oxygen 18 to\naerodynamic feedback process that\nOxygen 16 ratios (a proxy measure of air\ndepends on the downwind distance (the\ntemperature). The correlations of dust\nfetch). That is, saltating sand grains could\nconcentration and air temperature have\nincrease the apparent aerodynamic\nbeen interpreted as reflecting different\nroughness height; this increase of\nsource areas, wind stresses over these\nroughness height could lead, in turn, to an\nsource areas, transport, and increased\ninternal boundary layer in which more\ndeposition rates due to climate change (and\nmomentum is transferred to the surface.\nto global warming in particular).\nThe increase in momentum exchange could\nthen cause even more surface particles to\nOn a regional scale, desertification\nbe suspended.\n(degradation of soil potential) of the land\nby wind erosion causes concentrations of\nThe second hypothesized cause for the\nsmall particles that exceed the PM-10\nfetch effect involves a change of the soil's\n(particle mass smaller than 10 um\nresistance to erosion with distance. This\ndiameter) limits in downwind cities, such a\nhypothesis followed from observations\nSpokane, WA, for example. One of the\nwhich showed that as the fraction of the\nmost serious manmade disasters of the\nfrontal area of nonerodible particles\ncentury, the nuclear contamination caused\ndecreased, more of the wind momentum\nby the accident at Chernobyl, was largely\nflux went to transporting soil through the\na problem of resuspension of particles,\nair. Because soil aggregates (including soil\nonce the initial contamination had settled.\ncrusts) would be expected to be\nincreasingly destroyed with increased\nThe ARL desertification and resuspension\nsandblasting, which itself increases as a\nproject relies primarily on outdoor\nfunction of distance from the leading edge,\nmeasurements and secondarily on\nthe same wind stress could transport more\nlaboratory studies. The\noutdoor\nairborne soil mass as distance increased\nexperimental sites are Owens Lake, located\nfrom the leading edge. This effect was\nnear Lone Pine, CA and the Jornada del\ndetected as a decrease of threshold friction\nMuerto Experimental Range located near\nvelocities with distance downwind.\n43","CLIMATE TRENDS AND VARIABILITY\nA recent resuspension model starts with\nresidual effect, responsible for a small\nthe premise that the emission of suspended\nfraction of the total fetch effect. The\nparticles from a surface is proportional to\ndominating large-scale (greater than 100\nthe surface vertical flux of kinetic energy\nm) fetch effect mechanism was found to\nby saltating grains and inversely\nbe the variation of threshold velocity on the\nproportional to the binding energy holding\nsurface of the lake.\nthe particles to the surface. Binding energy\nof fine particles to larger aggregates varies\nThe vertical flux of particles smaller than\nwith differences in soil texture (that is, the\n10 um was estimated for a site at Owens\nsize distribution of soil particles), chemical\n(dry) Lake in California. The vertical flux\ncomposition of the soil, clay mineralogy,\nwas estimated using the profile method\nsalt and organic content, and physical\nand provides a valuable data point for loam\nproperties of the soil such as the\ntextured soils that was not available\n(changing) size distribution of soil\nbefore. The Owens Lake data are\naggregates as affected by wetting, drying\nconsistent with those for other soil\nfreezing, thawing and erosive processes\ntextures and suggests that the binding\nsuch as sandblasting. The\nARL\nenergy postulated in the recent model is of\nmeasurements have added important field\nthe same order as that for sandier soils.\ndata for evaluating the assumptions of this\nrecent model, and for refining the\nOther important problems in resuspension\nformulations on which the model is based.\nare being studied at Owens Lake and the\nJornada del Muerto Experimental Range.\nConclusions.\nThese problems include: the effect of\nlimitation of particle supply on the flux of\nThe data from the Owens Lake\nresuspension particles, the vertical flux of\nexperiments confirmed the importance of\nsmall (< 10 um diameter) particles, and\neach of the two hypothesized mechanisms,\nthe breakup of natural crusts.\nalong with an older \"soil avalanching\"\nmechanism. Thus, the studies have\nrevealed that there are three mechanisms\nthat cause the wind-erosion fetch effect -\navalanching, soil resistance, and\naerodynamic feedback.\nThe distinctive consequences of\naerodynamic feedback were observed for\nthe first time during one of the ARL Owens\nLake tests, in March 1993; progressive\ndisintegration of soil crust by sandblasting\ncaused a decrease of threshold friction\nvelocity with distance from the unbroken\ncrust. The gradient of threshold friction\nvelocity contributed to an opposite gradient\nof soil flux. The avalanching effect is\nimportant for small-scale (of the order of a\nfew meters) wind erosion fetch effects. At\nthe leading edge separating nonerodible\nmaterial from erodible material, it is a\ndominating effect. For scales of more than\n50-100 m, however, avalanching is a\n44","CLIMATE TRENDS AND VARIABILITY\nCLIMATE CHANGE AND THE IPCC\nContributions to the IPCC Second Scientific Assessment\nBackground.\nappear in early 1996. ARL has contributed\nmaterial on metadata, tropospheric and\nThe Intergovernmental Panel on Climate\nstratospheric temperature, and water vapor\nChange (IPCC) was jointly established in\nto this effort, and has also served among\n1988 by the World Meteorological\nthe reviewers of the draft to be submitted\nOrganization (WMO) and the United\nto the Panel this year.\nNations Environmental Program. Its\npurpose is to provide the world's\nMetadata.\ngovernments with authoritative summaries\nof the prospects for long-term climate\nThe collection and analysis of metadata\nchanges resulting from human activities.\nabout worldwide radiosonde observations\nSeveral ARL scientists of the Silver Spring\nis a critical step in the ARL effort to\nHeadquarters Division are Contributors to\nseparate true changes in climate from data\nthis effort. The ozone and temperature\nartifacts. The radiosonde metadata\nwork is also included in summaries for the\ncollection began several years ago when all\nStratospheric Processes And their Role in\nthe member nations of the WMO were\nClimate (SPARC) Project of the WMO.\nformally requested to provide historical\ninformation about radiosonde stations in\nThe ARL focus is on climate records from\ntheir networks. That survey yielded\nupper-air observations. Effects of such\nhistorical information from about 50\nnatural but irregularly occurring phenomena\ncountries. Additional information is being\nas volcanic explosions and El Niño events\ncollected from libraries and by interviewing\nare studied, to help extract long-term\nexperts in particular countries. The\nclimate change signals from records of\nresulting historical information is currently\ntemperature in the troposphere and lower\nbeing assembled in a consistent electronic\nstratosphere, water vapor in the\nformat. A striking example of an apparent\ntroposphere, and total and stratospheric\nchange in temperature is shown in Figure\nozone. Other quantities examined are\n1, where a change in radiosonde sensor at\ncloudiness and sunshine over the U.S. and\nTahiti coincided with the \"drop\" in\nhigh level tropical winds and temperatures\ntemperature in 1976.\nas indicators of the Quasi-Biennial\nOscillation (QBO). The data records begin\nTemperature.\nat various times but each is now at least\n22 years long. The bulk of the data\nVirtual temperature for the troposphere,\noriginate from routine radiosonde\ntropopause layer and lower stratosphere\nobservations, so there is particular\ncontinue to be analyzed using data from a\nsensitivity to questions of record\nnetwork of radiosonde stations, chosen to\nhomogeneity. Thus historical metadata are\nprovide uniform geographic coverage. In\ncompiled, that is, information about the\nthe troposphere the 37-year record shows\nsensors used and the methods of data\na warming of about 0.1°C per decade,\nprocessing and any other information that\ndespite a nearly constant temperature since\nwould affect the interpretation of the data.\n1979 (see Figure 2). This shorter period\ncoincides with the satellite temperature\nThe IPCC is currently preparing a new\nestimates which also show virtually no\nreport on climate change, scheduled to\nwarming. Because the end of this period is\n45","CLIMATE TRENDS AND VARIABILITY\ninfluenced by the eruption of Mt. Pinatubo,\nexamined. In addition, both the QBO and\nit would be premature to take this period as\nthe irregular injection of particles into the\nevidence that any long-term warming has\nstratosphere by volcanos affect\nstratospheric temperatures. All these\nceased.\nfactors must be considered in extracting\nGlobal tropospheric temperature anomalies\nany long-term signal from the data record.\n0.6\n0.5\n0.4\nWater Vapor.\n0.3\n0.2\nFor the humidity studies, nearly 1000\n0.1\n0.0\nstation records since 1973 have been\n-0.1\nexamined and about 800 retained for\n-0.2\nanalysis. A preliminary global climatology\n-0.3\nof water vapor in the air column below 300\n-0.4\n-0.5\nmb has been constructed. (This represents\n-0.6\nwell over 95% of the water in the total\n1955\n1960\n1965\n1970\n1975\n1980\n1985\n1990\n1995\ncolumn.) It is preliminary because there are\nFigure 1. Monthly mean 100 mb\nstill station records to be examined for\ntemperatures from Tahiti. The break in\ndiscontinuities. Some of the results\n1976 coincides with a temperature sensor\nobtained so far have been provided to\nchange from bi-metal to thermistor.\nscientists at Colorado State University,\nwho have combined them with satellite\ndata to obtain a more complete picture of\n100 millibar temperature record from Tahiti\nthe global atmospheric water vapor picture.\n-65\nSatellites can provide more detail on water\nvapor at high elevations and above regions\nlacking radiosonde observations, e.g. over\n-70\nremote ocean areas and some continental\nareas with few observing sites.\n-75\nBased on stations selected for their\nrelatively homogeneous data records, a\n-80\n1955 1960 1965 1970 1975 1980 1985 1990 1995\nseparate climatology of water vapor above\nNorth America has been constructed. The\nFigure 2. Mean annual virtual temperature\ndata show a gradual increase in\nanomalies for the 850-300 mb layer from\natmospheric water vapor content in the last\nthe 63-station network.\n21 years over most of the region; at many\nstations the trend is statistically significant.\nIn the stratosphere and in the 300-100 mb\nThe exceptions are northern and eastern\nlayer, there has been some cooling since\nCanada where slight decreases are found.\n1958. Satellite observations agree on the\nIn general the increases and decreases\nstratospheric cooling since 1979, but show\nparallel changes in temperature, i.e.\na smaller magnitude. Unfortunately,\nwarming is associated with rising water\nsatellites do not give an estimate for the\nvapor and cooling with decreasing water\n300-100 mb layer, where the cooling was\nvapor, as illustrated in Figure 3. Relative\nvery pronounced in 1993 and 1994. Some\nhumidity also tended to increase but the\nof the apparent cooling may reflect\nincreases are less often significant.\ninhomogeneities in radiosonde\nobservations, like the one illustrated in\nIn October, 1994, W. Elliott and D. Gaffen\nFigure 1. This possibility is being\nconvened 125 scientists at Jekyll Island\n46","CLIMATE TRENDS AND VARIABILITY\nGA for an AGU Chapman Conference on\natmosphere, although the seasonal cycle is\nThe Role of Water Vapor in the Climate\nreasonably well simulated.\nSystem. The purpose was to bring\ntogether those modeling water vapor's\nCloudiness and Sunshine.\ndistribution and its effect on radiative\ntransfer with those using a variety of\nBecause clouds reflect sunlight, a time\ntechniques to measure it.\nseries of one of these would be expected\nto be a mirror image of the other; for the\nBecause water vapor is key to both\nmost part this has been true over the U.S.\nradiative transfer and the global\nsince 1950 (Figure 4). The slight increase\nhydrological cycle, it is important to\nin cloudiness since 1958 mostly reflects\nevaluate how well global climate models\nthe reduced cloudiness of the early 1950s\nsimulate water vapor. As part of the\n(Little Dust Bowl). Since 1965 there has\nWMO-sponsored Atmospheric Model\nbeen little trend in clouds although there is\nIntercomparison Project, ARL is involved in\na clear association of cloudiness and the\na diagnostics subproject comparing the\noccurrences of El Niño. During El Niño,\nsimulations from about 30 general\ncloudiness tends to be above average,\ncirculation models with radiosonde\nparticularly in the southern tier of states.\nobservations. Preliminary results indicate\nThe prolonged El Niño of 1991-94 has\nthat most models seem to underestimate\nbeen associated with U.S. cloud cover 1-\nthe amount of water vapor in the\n2% above average.\nSfc-500mb PW\nAnnual Trends\n1200 UTC\n(% /decade)\n90N\n80N\n70N\n-5.0\n0.0\n60N\nIII\n0.0\n5.0\n15\n50N\nIII\nII\n5.0\n10.0\nIII\n40N\n30N\nIII\nExceeds 95%\n20N\nLevel\n10N\nON\n180W\n160W\n140W\n120W\n100W\n80W\n60W\n40W\nFigure 3. Trends in precipitable water over North America, based on radiosonde stations\nbased on 1973 to 1993 records obtained at 1200 UTC. The units are % of annual mean per\ndecade.\n47","CLIMATE TRENDS AND VARIABILITY\nU.S. cloud cover and sunshine duration\n65\n60\n60\n1950\n1955\n1960\n1965\n1970\n1975\n1980\n1985\n1990\n1995\nFigure 4. Mean Annual Sunshine (upper\ncurve) and Cloudiness (lower curve) over\nthe U.S. since 1954. Units of both curves\nare % possible sunshine and % (daytime)\ncloud cover.\nOzone.\nThe ground-based Dobson network shows\na global decrease of stratospheric ozone of\nabout 5% over the past 37 years of\noperation, with most of that occurring\nsince 1980. Above the north temperate\nregion the decrease has been nearly 10%.\nMost of the decrease is seen in the lower\nstratosphere rather than the high\nstratosphere as originally anticipated. The\ntotal column ozone reached a record low\nvalue in 1993 and recovered slightly in\n1994. The low values can be attributed in\npart to the Pinatubo eruption which\ndecreased ozone in the 16-24 km layer by\nalmost 20%. By comparison, after El\nChichon's 1982 eruption, low stratospheric\nozone decreased by about 10% and after\nFuego's 1974 eruption it decreased by\nabout 5%.\nTropospheric ozone, as recorded by\nozonesondes, showed increases in the\nnorth temperate region of about 20% from\n1968 to 1980. However, since 1980 the\nrecord shows almost no increase in the\ntroposphere and there is some indication of\na slight decrease in the 1990s. This\nfinding may be now slowly penetrating the\nozone literature but it has not been widely\nrealized.\n48","CLIMATE TRENDS AND VARIABILITY\nISIS\nThe Integrated Surface Irradiance Study\nBackground.\nperspective. For example, the Albuquerque\nNWS station moved to new quarters in\nISIS is a new network of radiation stations,\nMarch 1994; ATDD installed a new data\ndistributed across the U.S.A., and made up\nacquisition system in time for a\nof two tiers - Level 1 stations make\nreplacement installation to be operational in\nrelatively straightforward measurements of\ntime for a seamless transition. Five\nincoming radiation, primarily visible but also\nadditional ISIS data retrieval systems were\nplanned to have UV-B broadband sensors;\ninstalled during 1994, and recalibrated\nLevel 2 stations make additional\nsensors were also provided. Meetings with\nmeasurements of outgoing and infrared\nNCDC officials were held, to design the\ncomponents. The Level 2 sites include the\ndata ingestion process for archiving ISIS\nsites sponsored by the NOAA Office of\ndata.\nGlobal Programs under their SURFRAD\nprogram. All ISIS sites will eventually have\nInstallation of the prototype ISIS site, in\nrotating shadow band radiometers,\nAlbuquerque NM, was completed in May,\ndesigned to provide a widespread picture of\n1994. Data are retrieved automatically,\natmospheric aerosol optical depth across\nevery day, via modem. This site has been\nthe U.S.A.\nviewed as a test case. It has operated\ncontinuously with 100% data retrieval\nLevel 1 of ISIS is partly intended to\nsince the installation of its full complement\nconstitute an up-dated continuation of\nof instruments. Measurements include\nmonitoring previously conducted by the\nglobal shortwave, normally incident\nNational Weather Service under its\nshortwave, UV-B (295-320), and\nSOLRAD program. Because of the changes\nphotosynthetically active radiation\nimposed by the modernization of the\n(400-700 u) under a rotating shadowband,\nNational Weather Service, many SOLRAD\nwith 15-minute statistics; these permit\nsites have been discontinued. Some of\nclear-sky turbidity estimation. Refurbished\nthese discontinued SOLRAD sites are\nsensors for ISIS are calibrated by DOE's\nplanned for replacement by new ISIS sites,\nNational Renewable Energy Laboratory\nat nearby locations.\n(NREL).\nThe goal is to generate a single, coherent\nThe Nevada Integrated Surface Irradiance\nnetwork, with common data recording,\nStudy (ISIS) site, historically operated by\ntransfer, and archiving characteristics, and\nthe NWS at McCarren Airport in Las Vegas,\nwith as much continuity as possible,\nis now scheduled to be moved to Desert\naddressing needs of the surface irradiance\nRock, Nevada (on the Nevada Test Site of\ncommunity and with components\nthe Department of Energy), where it will be\naddressing each of IR and UV radiation.\noperated by ARL personnel of the Special\nOperations and Research Division, Las\n1994 Activity, Level 1.\nVegas.\nImpacts of the NWS modernization were\n1994 Activity, Level 2.\nfelt at many historic SOLRAD locations,\nand each was reviewed from the ISIS\nThe first SURFRAD site (Bondville, IL) was\nsuccessfully set up in April. Shakedown\n49","CLIMATE TRENDS AND VARIABILITY\nproblems were solved within the first\nFollowing these installations, the search for\nmonth, and since then data have been\nthe last three SURFRAD sites has\nretrieved continuously.\ncommenced in earnest.\nThe Fort Peck (Montana) SURFRAD site\nWork began on the Table Mountain\nwas installed in mid November. The site is\n\"SURFRAD\" site simulation, intended to\nlocated near a homesite on land owned\nprovide a working model of a SURFRAD\njointly by the Assiniboine and Sioux Tribes.\nsite within easy reach of Boulder, CO. The\nThe homesite resident was trained to care\ninstrument set contains all instruments of\nfor the instruments; a local Electronics\na SURFRAD site and a shaded pyranometer\nEngineer from the Fort Peck Community\nand pyrgeometer have been added. As in\nCollege will handle technical problems. In\nthe case of all SURFRAD (and ISIS) sites,\nearly December, the SURFRAD facility at\ntelephone data transfer is planned.\nthe Goodwin Creek Experimental Basin in\nnorthwestern Mississippi was installed.\nResults.\nWith the Bondville, Illinois SURFRAD\nstation already operational, these recent\nThe diagram below illustrates the kind of\ninstallations complete the first sub-array of\ndata obtained automatically from SURFRAD\nSURFRAD sites. An additional three sites\nsites. The example shown is of data\nare anticipated. Agreements between\nobtained at Bondville, Illinois, during a\nNOAA and the host organizations are based\nsolar eclipse.\non an expectation that they will\naccommodate the SURFRAD sites for at\nArrangements are presently being made for\nleast 25 years.\nISIS data to be available via the World\nWide Web. It is expected that today's data\nwill be available tomorrow.\n1000\n800\n600\n400\n200\n0\n0\n600\n1200\n1800\n2400\nCentral Standard Time\nFigure 1. Radiation observations made at the Bondville, Illinois, SURFRAD/ISIS station on the\nday of a solar eclipse.\n50","CLIMATE TRENDS AND VARIABILITY\nATMOSPHERIC OPTICS\nVisibility and Turbidity\nBackground.\nthe Grand Canyon Visibility Transport\nCommission Aerosol and Visibility\nARL specializes in the geochemical cycling\nSubcommittee, Marc Pitchford continued to\nof atmospheric aerosols, particularly the\nparticipate in GCVTC activities, which have\nparticulate component. Research groups in\nmoved into an integrated assessment\nARL concentrate on the injection of dust\nmode. An intensive meeting was held with\nand soil particles into the atmosphere\nthe GCVTC Assessment Subcommittee in\n(addressed elsewhere in this document),\nDenver, Colorado. The Assessment\nthe transport of particles through the\nSubcommittee has selected contractors to\natmosphere, the production of aerosol\ndesign computer software that will\nparticles in the air by chemical reactions,\ncombine all of the input data needed for an\nthe scavenging of airborne particles by\nassessment (economic, social, emissions,\nclouds and their subsequent deposition in\natmospheric processes, optical effects,\nprecipitation, the dry deposition of particles\npopulation growth projection, etc.) to allow\nas air moves across different landscapes,\npolicy makers to test the effects of various\nand the assembly of numerical models.\nemission management options.\nThe\ntechnical subcommittees are responsible\nThrough its long-standing involvement with\nfor generating the required input data and\nWMO, ARL remains active in the study of\nevaluating the use of these data in the\nturbidity (mainly involving the Silver Spring,\nassessment. GCVTC recommendations on\nBoulder, and Oak Ridge teams).\nthe protection of visibility at national parks\nIndependently, ARL plays a strong role in\nand wilderness areas on the Colorado\nthe nation's research related to visibility\nPlateau are required by law by fall of 1995.\n(centered at Las Vegas). The two\nconstitute a major program with a common\nChairmanship of the Steering Committee\ntheme of \"atmospheric optics.\"\nfor the Interagency Monitoring of\nPROtected Visual Environments (IMPROVE)\nVisibility.\nProgram also now resides within SORD.\nThe IMPROVE organizational Memorandum\nSince the transfer of SORD (Las Vegas)\nof Understanding (MOU) was refined. This\npersonnel from the National Weather\nMOU is designed to formalize the\nService to ARL early in 1994, a coherent\ncooperation and integration of\nprogram on atmospheric optics at the\nvisibility/aerosol monitoring sites,\nNevada Test Site is slowly evolving.\nnationwide. Six federal agencies including\nNOAA, and three organizations\nThe intent is to develop a research program\nrepresenting state air quality control\nat SORD that is consistent with the\nagencies cooperate in the management of\ndivision's Department of Energy (DOE)\nIMPROVE. A final version of the MOU was\nsupport role at the Nevada Test Site (NTS)\nready for Agency review at the end of\nand with NOAA's research goals.\n1994.\nThe organizational changes at Las Vegas\nTurbidity.\nserved to consolidate a number of\npreviously unconnected activities within\nTwo activities focus on atmospheric\nthe ARL/SORD program. As Chairman of\nturbidity (or aerosol optical depth). The\n51","CLIMATE TRENDS AND VARIABILITY\nfirst activity is a consequence of earlier\nSome practical applications of atmospheric\nARL participation in an extensive\nextinction data do not require exceedingly\nexamination of turbidity data archived be\nhigh accuracy but rather continuing long-\nNOAA on behalf of the WMO, and derived\nterm precision. Relative measurements\nfrom sunphotometer observations at\nthat encapsulate changes in scattering\nregional sites of the WMO Background Air\nconditions can be made at small cost but\nPollution Monitoring Network (BAPMoN).\nwith lasting benefit. Such measurements\ninclude monitoring the relative magnitude\nWith the redefinition of the WMO global\nof the direct and diffuse irradiance\nmonitoring activity, and the starting of a\ncomponents in an optically active portion\nnew Global Atmosphere Watch to subsume\nof the solar spectrum. A single sensor that\nthe highest quality components of\nis periodically shaded by a rotating shadow\nBAPMoN, the question arose as to whether\nband provides adequate data for many\nany elements of the BAPMON turbidity\npurposes of this kind. The simplest form\nprogram should be transferred to GAW. A\nof rotating shadow band radiometer is of\nfour-member committee was set up by\nthis type. A single silicon cell quantum\nWMO to recommend actions. The report\nsensor is mounted horizontally at the\nof this committee was prepared by ARL. In\ncenter of the sphere described by a rotating\nbrief, the committee found few redeeming\nband, thick enough to provide a short\nfeatures in the current archive, and\nperiod of shade but narrow enough to\nrecommended that the long-standing\nminimize errors in the measurement of total\nsunphotometer observation program should\nirradiance. Broad-band data are collected\nbe discontinued and replaced by a new\nautomatically, usually at intervals short\nprogram making full use of modern\nenough to ensure that a representative\nadvances in the related science.\nfully-shaded value is reported for each brief\npass of the shadow-band.\nDuring 1994, the future of the GAW\nturbidity program was clarified. A formal\nThe data derived using this automatic\nreport on a meeting of experts (hosted by\ndevice lend themselves to routine\nARL at the end of 1993) was prepared and\nexamination using a standard Langley plot\nis currently in press.\napproach. In addition, however, it is useful\nto quantify the variable L = (D/I).cos(5)\nRotating Shadow Bands.\nfrom indicated values of the diffuse (D) and\ndirectly incident (I) radiation detected by\nThe second activity relates to the\nthe horizontal sensor, where 5 is the solar\ndevelopment and optimal use of various\nzenith angle.\nkinds of rotating shadow band radiometers.\nThere are three variations now in use, each\nRotating shadow band sensors will be\nwith a specific purpose but each also\ndeployed at all radiation monitoring sites of\nemploying an identical measurement\nARL (ISIS Levels 1 and 2 - SURFRAD). The\nphilosophy - as much as possible to\nconfiguration addressed above is designed\ndepend on the use of a single sensor to\nfor ISIS Level 1 application. More\nmeasure different irradiance components,\nadvanced devices of the same general\nto minimize difficulties caused by sensor\nphilosophy are used at all SURFRAD sites.\ndeterioration and to minimize the\nconsequences of different sensor\nperformance characteristics when operating\nin a spatial array.\n52","EMERGENCY PREPAREDNESS\nATMOSPHERIC TRACER STUDIES\nStudies of Air Mass Trajectories and Dispersion\nBackground.\nm tower with basic meteorological\ninstrumentation was utilized, with five\nThe Field Research Division of ARL, in\nlevels of vertical sampling supporting an\nIdaho Falls, ID, has made a specialty of\narray of ground samplers.\nusing atmospheric tracers to explore flow\nand dispersion in demanding circumstances\nIn July, FRD employed a new portable\nand to test the predictions of models. A\nchemical dispensing system (necessitated\nnumber of notable experiments have been\nfor operator safety - some of the\nconducted in past years, many involving\nchemicals that were studied were\nother ARL divisions (particularly Silver\nhazardous) for a tracer study utilizing Grid\nSpring, Research Triangle Park, and Oak\nIII at the INEL.\nRidge). The tracers of choice range from\nthe fairly common sulfur hexafluoride to\n\"Smart\" Tetroons.\nseveral far rarer perfluorocarbon\ncompounds. Zero-lift tetroons are also\nDuring 1994, the FRD team worked on the\nused, sometimes fitted with transponders\ndesign of adjustable lift tetroons for the\nto relay their GPS position in response to\nACE-1 study (of atmospheric chemistry\nradar interrogation.\nover remote oceans), planned for late 1995\nin the Southern Ocean. The tetroons will\nMany model tests make use of the tower\nbe used to help track the location of the air\ngrid set up and maintained by FRD on the\nparcel being sampled.\nreservation of the Idaho National\nEngineering Laboratory. The FRD Grid III\nThe tetroons are designed to adjust their\narea is especially rich in meteorological and\nlift to compensate for any slow ascent or\nsampling sensor arrays. The winds at the\ndescent remaining after balancing for zero-\nINEL site are very predictable, leading to\nlift at the time of launch. Previous\nreduced experimental costs. FRD has\nexperience indicated that it is exceedingly\nreceived permission from the EPA and the\ndifficult to adjust the lift so that a standard\nState of Idaho to release several tracer\ntetroon will not \"ditch in\" to the ocean\ngases over Grid III, in support of a number\nwithin 12 to 24 hours. The ACE-1\nof effluent-detection test programs.\nexperiment is designed to track the\nchanging atmospheric chemistry in a parcel\n1994 Activity.\nof air that is identified by a marker tetroon,\nover a period of several days. The smart\nA March/April study was conducted at Fort\ntetroon is intended to serve this purpose.\nBliss in El Paso, Texas, to test the remote-\nsensing capabilities of a new Mobile\nThere is an additional important advantage\nAtmospheric Spectrometer (MAS) and to\nof the advanced tetroon system to be used\ncheck chemical reconnaissance systems\nin ACE-1: the tetroons also carry a\nthat are available for use in a battlefield\nminiaturized Global Positioning System that\nenvironment. The MAS is a spectroscopic\nautomatically reports the balloon location\nand radiometric measurement system\nto a receiving station some considerable\ndesigned to measure trace gas\ndistance away.\nconcentrations and profiles remotely. A 10\n53","EMERGENCY PREPAREDNESS\nETEX.\nparameterizations lead to the large\nvariations that were observed.\nThe Headquarters Division of ARL (Silver\nSpring) has been heavily involved with\nThe first ETEX tracer release, from\nlong-range tracer dispersion studies in\nBrittany, occurred Sunday October 23,\nNorth America. During 1994, the first\nstarting at 1600 UTC, after the passage of\nEuropean tracer release for evaluating\na trough. The expected transport pattern\ndispersion model predictions was\nwas right into the center of the ground-\nconducted. The ETEX sampler array is\nlevel sampling network. Aircraft sampling\nshown in Figure 1.\nthe next day, about 400 km downwind,\nmeasured tracer above the boundary layer.\nThe European Tracer Experiment (ETEX)\nThe NOAA plume forecasts agreed closely\nstarted with a series of tests of the models\nwith those produced by the U.K.\ninvolved. Preliminary model results (\"dry\nMeteteorological Office and the Canadian\nruns\") showed large differences between\nMeteorological Center.\nsome of the participants, especially in\nterms of maximum concentrations. It was\nA second tracer experiment was\nsuggested that a combination of large\nsubsequently conducted, and results are\nvertical shears in the horizontal wind and\ncurrently being examined. About\n20\ndifferences in vertical diffusion\ndispersion modeling groups took part.\nETEX sampling stations\nFigure 1. The network of surface samplers deployed for the European Tracer EXperiment\n(ETEX) of 1994 and 1995.\n54","EMERGENCY PREPAREDNESS\nDISPERSION STUDIES\nBasic Investigations of Plume Behavior\nBackground.\ninfluences the observed winds at several\nsites west of Oak Ridge. Simulations\nClassical studies of atmospheric diffusion\ngenerated by a hydrostatic mesoscale\nhave been conducted over simple surfaces\nmodel are being used to support the data\n-- flat, with homogeneous surface cover.\nanalysis. A number of modifications were\nThe real world is substantially different.\nmade to improve the model's performance,\nFrom the perspective of power plant siting,\nsimplify data input, and greatly increase\nproper account needs to be taken of\nexecution speed.\ntopographic influences, to ensure that\ntopography does not direct emissions\nNumerical simulations of the Tennessee\ntowards urban areas, sensitive ecosystems,\nValley using a hydrostatic mesoscale model\netc. From the viewpoint of legal\nwere conducted, starting with two sets of\ncompliance, terrain effects can cause\nsimulations representative of summer\nplumes aloft to contact the surface,\nconditions, and a third set representing\nresulting in exceedences that would not\nwinter conditions. The simulations are\noccur over flat land. These two views\nbeing compared with tower observations\ncorrespond, to a large extent, to the\ncollected in the Tennessee Valley (using\ndifferent focusses of complex terrain\nthe array illustrated in the accompanying\nstudies conducted at Oak Ridge and at\nsummary of studies of nocturnal\nResearch Triangle Park, under DOE and\ndispersion). Both the model simulations\nEPA sponsorship, respectively.\nand the tower data show a distinct\nupvalley (southwest) flow during the day.\nMeanwhile, ARL workers at Idaho Falls and\nAt night, the tower data show some\nat Las Vegas are actively exploring new\nevidence of a general downvalley drainage\ntechnologies for studying plume behavior,\nflow, whereas the model simulations are\nboth in simple and in complex terrain.\nmore strongly influenced by drainage off\nthe valley sidewalls. Attempts are now\nbeing made to quantify the relative\nASCOT.\nimportance of various flow mechanisms\nThe ARL/ATDD group at Oak Ridge have\nwithin the valley.\nbeen major participants in the DOE-\nsponsored Atmospheric Studies of\nPreliminary calculations of gravity\nCOmplex Terrain (ASCOT) program for\nwave-induced drag on the planetary\nmore than a decade. During 1994, work\nboundary layer using the ATDD hybrid\nconcentrated on dispersion regimes in the\nPBL-gravity wave model were completed,\nridge/valley terrain of the Tennessee Valley.\nwith encouraging results.\nThe\nData from an Oak Ridge meteorological site\none-dimensional time-dependent PBLmodel\nsurvey were used to study diurnal\nis initialized with an Ekman wind profile\nvariations of wind speed and direction at\nand a linearly increasing potential\nvarious sites in the valley. Thermally\ntemperature gradient. The flow is\ndriven circulations were found to be more\nsimulated over a two-dimensional ridge.\nimportant than anticipated. There is also\nWave stress is calculated every five\nevidence that flow through a gap in the\nminutes of the simulation, and the vertical\nwestern sidewall of the Tennessee Valley\ndivergence of the stress is added to the\n55","EMERGENCY PREPAREDNESS\ndivergence of the turbulence stress. The\ndownslope flow on plume impacts. The\nwave-induced drag is found to strongly\npublished comparisons suggest that\ndecelerate the PBL flow.\nCTDMPLUS yields reasonable estimates\neven in the presence of downslope flows\nPlume Impaction.\non windward terrain.\nOver the last decade, extensive studies of\nPlume Detection.\nflow and dispersion over and around\nisolated hills culminated in the development\nThe\n\"Crystal Mist\" experiment was\nof the EPA Complex Terrain Dispersion\nconducted on the Nevada Test Site in July,\nModel (CTDM). A family of specialized\nto test capabilities to track the dispersion\nmodels has evolved from CTDM. During\nof a silicon bead cloud (soda lime) released\n1994, ASMD scientists completed a\nabove the convective boundary layer.\nsensitivity test of the Industrial Source\nRemote measurements of the cloud were\nComplex - COMPlex terrain DEPosition\nmade using a Lidar.\n(ISC-COMPDEP) model to various inputs\nincluding particle size distribution, particle\nThe Crystal Mist study was jointly\ndensity, scavenging coefficients, resolution\nsponsored by the Department of Defense\nof the particle size distribution, and terrain\n(DOD) and the Department of Energy\ngrid resolution. Maximum concentration\n(DOE).\nand dry and wet deposition values were\nexamined. The dry deposition values were\nARL/SORD meteorologists wrote a program\nfound to be most sensitive to the\nto calculate winds as frequently as the data\nspecification of the particle size\nwould allow, for fine structure analysis of\ndistribution. The wet deposition values\nthe atmosphere. Additionally, the standard\nseemed most sensitive to the specification\nSORD PIBAL software was modified to\nof the scavenging coefficients.\naccommodate the many extra levels that\nwere available from the body of\nThe influence of terrain-generated\nmeteorological data. The modifications\ndownslope (or upslope) flows on pollution\nallowed for up to 600 input levels and for\nconcentrations in plume impacts remains\na corresponding output capability.\nsomewhat contentious. During 1994, the\nJournal of Applied Meteorology (JAM)\nAt Idaho Falls, field support was given for\nreceived a comment on a 1992-published\nanother Department of Defense exercise,\narticle on ASMD's Complex Terrain\nthe Plume Dispersion Modeling Study. FRD\nDispersion Model (CTDMPLUS). It was\ndeveloped portable chemical dispensing\nasked if the estimates from CTDMPLUS\nequipment for CONUS test/experiment\nwere reasonable in the presence of\nsites. Grid III at the INEL is the standard\ndownslope flow on the windward face of\nfield setting for such studies.\nterrain. In response, it was stated that\nlittle is known about the influence of\n56","EMERGENCY PREPAREDNESS\nSTUDIES OF NOCTURNAL DISPERSION\nThe Fallacy of Decoupling\nBackground.\nattention. Data from an intensive study of\nwind fields in the Oak Ridge area were\nIt has long been assumed that atmospheric\nreanalyzed. PBL breakdowns were\nstability at night often becomes sufficient\ndetected using both conditional sampling of\nto prohibit turbulence and hence to permit\nthe wind speed-temperature covariance\npollutants aloft the be carried for long\ntime series, and wavelet analysis of the\ndistances without ground contact. The\nwind speed and temperature time series. A\nvarious tracer studies conducted by ARL\nspecific goal was to relate the statistics of\nover the last twenty years (e.g. CAPTEX,\nthe PBL breakdown events (e.g., number of\nANATEX) have demonstrated that this\nbreakdowns per night, duration of the\nargument is flawed. Vertical mixing can\nbreakdowns, breakdown strength) to the\nand does occur, even when stability\nPBL stability. These events are likely major\nregimes are conceptually prohibitive. The\ncontributors to nocturnal dispersion and\nnotion of intermittent bursts of turbulence\nair-surface exchange.\narose, and has since developed into a\ncentral theme for many contemporary\nThe study of interactions between\nresearchers.\nturbulence and atmospheric gravity waves\nhas historically been directed at the middle\nEarly studies of trace gas concentrations\nto upper atmosphere, where waves play an\nnear the surface revealed the signature of\nimportant dynamic role. It is now known\na phenomenon that has since become more\nthat in the nighttime planetary boundary\nwidely recognized: at night, periodic bursts\nlayer, say within the lowest 1 km of the\nof turbulence maintain \"contact\" among\natmosphere, gravity waves are also\nthe various layers of the lower troposphere,\nimportant, especially over hilly terrain. For\nand with the surface. The\nexample, hills and ridges with height and\nvery\nintermittency of this phenomenon caused it\nwidth scales of 100 m and 1000 m\nto be overlooked in many early field\nrespectively can generate vertically-\ninvestigations, since a micrometeorological\npropagating gravity waves under typical\n\"run\" containing one of these bursts of\nnighttime conditions. These waves can\nturbulence would probably have been seen\ngrow in amplitude as they propagate\nas \"non-stationary\" and would therefore\nupwards. If the amplitude grows too great,\nhave been excluded from the data sets\nthen the waves can break down,\nselected for further scrutiny. Now, it is\ngenerating regions of turbulence and\nknown that the \"noise\" of previous\nenhanced dispersion. \"Clear air\nresearchers has become the \"signal\" that it\nturbulence\" is a related phenomenon. Such\nis now necessary to understand.\nprocesses are not considered in\nconventional turbulence and dispersion\nNocturnal Turbulence and Gravity Waves.\nexpressions, and hence turbulence and\ndiffusion in the nighttime lower atmosphere\nNocturnal mixing and the evolution of the\nare often underestimated. The research\nnocturnal boundary layer are specialties of\nunder way at Oak Ridge focuses on how to\nOak Ridge ARL researchers. Turbulent\naccount for wave-generated turbulence and\nbreakdowns of the stable planetary\ndispersion in numerical models.\nboundary layer (PBL) receive special\n57","EMERGENCY PREPAREDNESS\nAn experimental component to this\nNocturnal Dispersion.\ninvestigation involves an array of surface\ntowers set up in ridge/valley terrain of the\nThe Army Research Office/ARL Workshop\nTennessee valley. Figure 1 shows the\non Turbulence and Diffusion in the Stable\ntower array constructed (the Regional\nPlanetary Boundary Layer was held at\nAtmospheric Measurement and Analytical\nArizona State University (Tempe). The\nNetwork - RAMAN) by bringing together\nmeeting was hosted by the Department of\ncapabilities of several organizations and\nMechanical and Aerospace Engineering.\naugmenting this array with towers\nThe workshop was well attended, and\noperated by NOAA/ATDD.\nconsiderable discussion followed each\npresentation. A detailed report is in\npreparation.\nNEW TAZEWELL\nRAMAN\nCLAIBORNE CO.\nHANCOCK CO\nMeteorological\nLAFOLLETTE\nHAWKINS CO.\nTower Network\nCLINCH-POWELL MTN. RANGE\nCAMPBELL CO.\nLegend\nE23\nSCOTT CO.\nMountains/Plateau\nUNION CO.\nGRAINGER CO.\nRidge-and-Valley Terrain\nMAYNARDVILLE\nMORRISTOWN\nCUMBERLAND MTNS.\nExisting RAMAN Sites\nAND PLATEAU\nHAMBLEN CO.\nGREENE CO\nE13\nProposed RAMAN Sites\nANDERSON CO.\nJEFFERSON CITY\nE05\nNY\nCLINTON\nE11\nKNOX CO.\nJEFFERSON CO.\nMORGAN CO.\nkm\nE03\nE02\n0\n10\n20\nE01\nE09\nE10\nE06\nE15\nKNOXVILLE\nNEWPORT\nHARRIMAN\nE07\nExisting Towers\nE04\nE30\nE08\nE19\nE20\nMountain Sites:\nSEVIERVILLE\nE05 Buffalo Mtn.\nROANE CO.\nGREAT-VALLEY\nE40 Cove Mtn.\nE12\nCOCKE CO.\nE49 Purchase Knob\nE67 Clingman's Dome\nLENOIR CITY\nRidge Sites:\nSEVIER CO.\nALCOA\nE09 Sharp's Ridge Firetower\nMARYVILLE E16\nE10 Y12 Water Plant\nLOUDON CO.\nE12 Lenoir City Firetower\nGATLINBURG\nE40\nBLOUNT CO.\nE13 Bluebird Ridge Firetower\nE19 Walker Branch Facility\nHAYWOOD CO.\nValley Sites:\nE14\nE01 NOAA-ATDD Townsite\nGREAT SMOKY MTNS.\nSWEETWATER\nE02 Oak Ridge Municipal Bldg.\nEA9\nE07 Y12 Waste Disposal Site\nE67\nTennessee\nE15 ORAU Scarboro Site\nMONROE CO.\nSWAIN CO.\nE20 ORNL 0800 Area\nNorth Carolina\nMAGGIEVALLEY\nFigure 1. The RAMAN network in eastern Tennessee, set up to investigate the extent and\ncauses of gravity waves and nocturnal turbulence bursts.\n58","EMERGENCY PREPAREDNESS\nAIRCRAFT WAKE VORTICES\nARL Studies Related to Aircraft Safety\nBackground.\nkept the issues before the public and\naviation industries. In July, Gene Start of\nFor many years, the ARL Field Research\nFRD provided testimony to the House\nDivision (Idaho Falls, ID) has conducted\nsubcommittee on Technology,\nstudies of the magnitude, persistence, and\nEnvironment, and Aviation. The hearing\nmotion of the vortices left by commercial\nwas on operational procedures for aircraft\nand some military aircraft. A test range on\nfollowing the Boeing 757 aircraft within\nthe Idaho National Engineering Laboratory\nterminal area airspace. The 1990 NOAA\nreservation is instrumented with tall towers\ntower flyby characterizations of the Boeing\ncarrying meteorological instrumentation and\n757, which included the B-757 wake\nphotographic equipment to record the wake\nturbulence data sets and the report\nvortices left by an aircraft flying between\nsummarizing those findings, were an\nthem. Studies of this kind have provided\nimportant part of that review. The hearing\ncritical information used by the Federal\nconcentrated on whether or not there was\nAviation Administration to specify, for\na procedural flaw in the FAA operational\nexample, safe distances for small aircraft\nplanning and incorporation of research\nto land or takeoff after larger aircraft.\nfindings into their air traffic control\nprotocols.\nThe unfortunate fatal crash of a Westwind\ncorporate jet at John Wayne Airport in\nAs a result of the continued attention, and\nOrange County California in late 1993\nin recognition of gaps in current\ngenerated widespread interest in the\nunderstanding, the entire issue of aircraft\naircraft wake vortex problem. The\nwake turbulence was re-addressed during\nWestwind was following a Boeing 757, an\n1994.\naircraft which was studied for its vortex\ncharacteristics by FRD in 1990. The FRD\nA reanalysis of the B-757 data previously\nwork received wide visibility because of\nobtained by FRD was sponsored by FAA.\nthis study and the recent crash. FRD\nThe reanalysis focused on the relationship\npersonnel who took part in the B-757 wake\nof vortex demise with ambient atmospheric\nvortex study were interviewed by\nturbulence. In parallel activity, new studies\nnewspaper and television reporters. In\nwere sponsored by FAA in support of\naddition, a series of articles appeared in\naircraft wake turbulence avoidance and\nAirline Pilot, the official magazine of the Air\nenhanced airport traffic capacity. An initial\nLine Pilots Association, depending heavily\nmeeting was conducted at NASA-Langley\non the FRD data. A subsequent article in\nin late January, with representatives of\nAviation Week and Space Technology also\nDOT, FAA, NASA, and NOAA (ARL/FRD).\ncited the FRD's research.\nIt was concluded that DOT, FAA, NASA,\nand NOAA should form a technical advisory\n1994 Activities.\ngroup to formulate plans and review\nproposed research aimed at resolving the\nFlight safety, aircraft operations, and\nknowledge gaps.\nprocedures for air terminals continued to be\na news media and industry concern\nA reanalysis of 1990 data obtained by FRD\nthrough 1994. Periodic media treatments\non wake vortices from B-727 and B-767\n59","EMERGENCY PREPAREDNESS\naircraft was also initiated, with a focus on\ndata from the half of the vortex that was\nderiving a relevant turbulence statistic from\nunaffected by the tower. Evaluations of\nthe hot film anemometer data, to describe\nthese and other potential mechanisms for\nvortex demise. The goal is to determine a\nextracting additional information from the\nrelationship of atmospheric turbulence with\nfield data set continued into 1995.\nvortex decay.\nThe search for relevant turbulence\nquantities was extended to a field\ninvestigation using new remote-probing\ninstrumentation. In October, 1994, a new\nlidar (developed by MIT Lincoln Laboratory)\nfor measuring aircraft wake vortices was\ndeployed at the Memphis, TN, airport. The\nlidar development had been funded by\nNASA. For this study, FRD characterized\natmospheric variables, including various\nturbulence and flux quantities. FRD also\ninstalled a RASS radar profiler and sodar at\nthe Memphis airport, to determine upper air\nturbulence characteristics. The field study\nended in December.\nThe 1990 FRD data on B-757 and B-767\naircraft were the foci of a Wake Vortex\nWorkshop held in Cambridge MA. This\ndata set has become the new standard for\ntesting vortex decay models. International\nparticipants included delegations from\nCanada, Germany, Great Britain, and\nFrance.\nFRD was also invited by the Canadian\ngovernment to review wake vortex work\ncurrently underway in Canada. The new\neffort uses the FRD 1990 wake vortex data\nin an international cooperative effort. The\nreview will consider modeling work being\ndone by Russian scientists under Canadian\ncontract on Boeing 757 and 767 aircraft.\nSeveral calculation algorithms were\ndeveloped for modifying vortex velocities\nas used in circulation calculations. These\nwere: 1) averaging the velocities on both\nsides of the vortex, 2) folding the data\nfrom one side of the vortex onto the other\nside using a least-squares fit, 3) using the\n60","EMERGENCY PREPAREDNESS\nFLUID MODELING\nBackground.\ndownwash could be a problem in the deep\nOhio River valley at this site and\nThe Fluid Modeling Branch of the\nrecommended a wind-tunnel.\nAtmospheric Sciences Modeling Division in\nResearch Triangle Park conducts laboratory\nA model of the terrain was constructed at\nsimulations of flow and dispersion in\na scale ratio of 1:480, representing a full-\ncomplex flow situations, including flow and\nscale section approximately 0.5 km wide\ndispersion in complex terrain, around\nand 5 km long. The river valley itself is\nobstacles such as buildings, and within\napproximately 150 m deep. The wind\ndense gas plumes. The Fluid Modeling\ndirection chosen was that expected to\nFacility employs large and small wind\nproduce the most severe terrain-downwash\ntunnels, a large water channel/towing tank,\neffects, i.e., with the most prominent hill\nand a convection tank.\ndirectly upwind of the stack. This model,\ncentered on the incinerator stack, was\nThe large wind tunnel has a test section\nplaced in the meteorological wind tunnel,\n18.3 m long, 3.7 m wide, and 2.1 m high.\nwith a simulated atmospheric boundary\nIt has an airflow speed range of 0.5 to 10\nlayer approaching it. Figure 1 shows a\nm/s, and is generally used for simulating\nview of the model installation.\ntransport and dispersion in the neutral\natmospheric boundary layer.\nMethane was metered from the model\nstack as a tracer to simulate the buoyant\nThe towing tank has a test section 25 m\neffluent, and flame ionization detectors\nlong, 2.4 m wide, and 1.2 m deep. It has\nwere used to measure concentrations,\na speed range of 0.1 to 1 m/s, and the\nprimarily ground-level values, downwind.\ntowing carriage has a range of 1 to 50\nThree stack heights were examined,\ncm/s. Generally, the towing tank is used\nincluding the existing stack height of 45.7\nfor simulation of strongly stable flow; salt\nm,thecalculatedgood-engineering-practice\nwater of variable concentration is used to\nstack height of 72.7 m, and an arbitrarily\nestablish density gradients in the tank,\nchosen \"tall\" stack height of 120 m (about\nwhich simulate the nighttime temperature\n80% of the valley depth). For each case,\ngradient in the atmosphere.\nconcentration patterns were measured over\na range of wind speeds to ascertain the\nA convection tank measuring 1.2 m on\nmaximum possible ground level\neach side and containing water to a depth\nconcentrations. The model was then\nof 0.5 m is used to study the convective\nrotated 180° and a similar set of\nboundary layer and flow and dispersion\nmeasurements was made. Finally, the\nunder convective conditions.\nterrain model was replaced by a flat-terrain\nmodel to quantify terrain effects relative to\nTerrain Downwash Study.\nflat terrain.\nAt the request of the EPA, a wind-tunnel\nNearly 50 cases were studied, to take into\nstudy of terrain downwash at the Waste\naccount the two dominant wind directions\nTechnology Industries (WTI) hazardous\nin the complex terrain as well as in the flat\nwaste incinerator located in East Liverpool,\nterrain, the three stack heights, and several\nOH, was conducted. A peer-review panel\nwind speeds for each combination of the\nthat examined the draft risk-assessment\nabove conditions. Most of the\nplan expressed concern that terrain-induced\nmeasurements were used to develop\n61","EMERGENCY PREPAREDNESS\nsurface concentration maps. These maps\nthe wind speeds at the stack top, which\nreveal that there is some slight indication\nshould increase the plume rise and reduce\nof the plume being directed around the\nthe maximum ground level concentrations.\nsouth side of this first hill.\nOn the other hand, the upwind hills tend to\nproduce downward wind velocities at stack\nWhereas a large number of surface maps\ntop and to increase the intensity of ambient\nand vertical profiles of concentration as\nturbulence; both these effects tend to\nwell as flow-structure and turbulence\nincrease the concentrations. The\nmeasurements were made, the results are\ndownwind hills also tend to increase\ndifficult to interpret from a scientific\nground level concentrations, but the degree\nof increase depends upon the hill shape.\nviewpoint.\nBuilding influences were also observed,\nMany interacting factors contribute to the\nalthough the present study was not\ndifferences in the ground level\ndesigned to investigate such. In spite of\nconcentration patterns observed as a result\nour inability to isolate and describe in detail\nof emissions from the WTI site and those\nthe specific causes of the results, the\nobserved from the same source in flat\nbroad picture is understood, and the\nterrain. The upwind hills tend to reduce\nconcentration patterns and values should\nbe eminently usable for the intended\npurpose.\nFigure 1. The physical model of the surroundings of the Waste Technology Industries\nhazardous waste incinerator, in East Liverpool, Ohio, as deployed in the wind tunnel.\n62","EMERGENCY PREPAREDNESS\nHEAVY GAS DISPERSION\nThe Nevada Spills Test Facility\nBackground.\nThe ARL Connection.\nCritical health and safety issues arise when\nFOUR ARL groups are involved in studies at\nheavy gases are accidentally released into\nthe Nevada spills facility.\nthe atmosphere. Such gases are life\nthreatening because of their behavior in the\nSORD (Las Vegas) provides\natmosphere. The dangers arise when\nclimatological services for experimental\nvolatile vapor clouds drift downwind. The\nplanning, meteorological monitoring during\nconcern is particularly intense in regions of\nthe experiment phase, and weather\nchemical industry and in areas around\nforecasts in direct support of the\nfacilities handling liquified natural (or\nexperiments. SORD meteorologists also\npetroleum) gas. There have been many\nprovide weather briefings and transport and\nspills that have underlined the hazards\ndispersion estimates to the test\ninvolved, culminating in the Bhopal (India)\nmanagement team. A SORD meteorologist\ndisaster of several years ago.\nserves on the LGFSTF DOE Safety\nAdvisory Panel.\nThe physics involved is complicated, since\ngases spilled as liquids are subject to a\nASMD (Research Triangle Park) has\nsurface phase change that complicates the\nrepresented EPA interests in the operations\nthermodynamics of the dispersion process,\nat the spills facility. Bill Petersen has\nand because the gases generated may well\nserved as the convenor and chairman of an\ndrift downhill, regardless of the direction of\ninteragency committee coordinating\nany prevailing wind. A key requirement is\nscientific studies utilizing the spills facility.\nto provide some objective methodology to\npredict when the terrain slope effect will\nATDD (Oak Ridge) has developed dense\ndominate the wind, and vice versa.\ngas dispersion routines ready to be tested\nagainst data obtained at the facility, and\nIt was partially to answer questions such\nparticipates in the related research\nas this that a Liquefied Gaseous Fuels Spill\nplanning.\nTest Facility (LGFSTF) was constructed on\na dry lake bed at Frenchman's Flat, on the\nFRD (Idaho Falls) has conducted several\nNevada Test Site and operated by the\nstudies at the facility, employing\nDepartment of Energy. The LGFSTF\natmospheric tracers. These studies have\naffords contracting agencies and\nbeen conducted for other agencies,\ncompanies the opportunity to conduct\naddressing the need to detect trace\ncontrolled spills of hazardous chemicals to\nquantities of airborne gases using remote\nassess mitigation techniques, protective\nprobing techniques.\nmeasures and chemical behavior. Various\nARL groups work in conjunction with the\nWind Tunnel Tests.\nspills facility, to help study the behavior of\nlarge spills of volatile liquids.\nA detailed experimental plan was\ndeveloped for wind tunnel tests of\n63","EMERGENCY PREPAREDNESS\ncandidate roughness arrays to be used in\nmeasure evaporation rates of chlorine and\nthe field in conjunction with dense gas\nammonia from spilled liquid pools. The\nreleases at the LGFSTF. The release site,\nprogram took place in August 1994.\na dry lake bed, is extremely smooth\n(roughness length = 0.2 mm), while the\n3. Effluent Tracking Experiment #2 (ETE\npetroleum industry-sponsored Petroleum\n#2). This was a second experiment in the\nIndustry Environmental Research Forum\nseries initiated in January, this time taking\n(PERF) experiment scheduled for August\nplace in August, 1994.\n1995 requires at least 100 times this\nroughness. Four different arrays of flat\n4. Dupont's Hands-On Training in the\nbaffles facing the wind will be tested in an\nMitigation and Cleanup of Sulfur Based\nexploratory physical modeling program,\nFuming Acids. The purpose of this\nwith an option to test an altered version of\nexperiment was to conduct mitigation and\nthe best array to achieve improved results.\ncleanup training on small spills of Sulfur\nTrioxide, 65% Oleum, and Chlorosulfonic\n1994 Field Studies.\nAcid. The study took place in September.\nThe CO2 and meteorological data from last\n5. Remote Sensor Test Range Program\nsummer's dense gas experiments at the\n(RSTR). The RSTR program was designed\nDOE Liquified Gaseous Fuels Spill Test\nto produce well-characterized, open-air\nFacility, Nevada Test Site, were analyzed\nplumes containing various concentrations\nto provide guidance for design of the\nof chemical vapors and aerosols, for testing\ninstrument array for the next tests to be\nremote sensing methods of detection. This\nperformed in September 1994. It was\ntest series was conducted in October\nfound that last year's results agreed quite\n1994.\nwell with the predictions of simple\nalgorithms resembling the Britter-McQuaid\nequations and nomograms. These plume\ndepth, plume width, mean concentration,\nand maximum concentration algorithms\nwere used to design sampler arcs for the\n1994 experiments, in which dense gas\nreleases were conducted at lower wind\nspeeds and with stronger stability than\never before attempted.\nA listing of specific experiments conducted\nat the Spills Facility is as follows.\n1. Effluent Tracking Experiment #1 (ETE\n#1). The purpose of the ETE # was to\ncharacterize stack emission concentration\nprofiles of simulated chemical\nmanufacturing processes.\nThe\nexperimental series started in January,\n1994, and lasted about three weeks.\n2. Evaporation Rate Measurements from\nChlorine and Ammonia Liquid Pools\n(ERMD). This program was designed to\n64","EMERGENCY PREPAREDNESS\nRSMC WASHINGTON\nRegional Specialized Meteorological Center\nfor Transport and Dispersion Model Products\nBackground.\nFollowing this demonstration, the NOAA\nRSMC was accepted by WMO and\nAs a result of the poor communications\nsubsequently became effective 1 July\nbetween countries following the Chernobyl\n1993. The addition of RSMC Washington\naccident in the Spring of 1986, the World\nresulted in two RSMCs per WMO region -\nMeteorological Organization (WMO) was\nWashington and Montréal for RA IV and\nasked by the International Atomic Energy\nToulouse and Bracknell for RA VI - and\nAgency (IAEA) and other international\nindicated the need to revise the interim\norganizations to arrange for early warning\narrangements. Under the new global\nmessages about nuclear accidents to be\narrangements, Region IV will be responsible\ntransmitted over the Global Tele-\nfor parts of Central and South America\ncommunications System (GTS). In addition\nRegion III), while Toulouse and Bracknell\nsome WMO member countries lacking\nwould cover the remaining Regions I and II\nextensive forecasting capability requested\n(Africa and Asia). These new global\nthat specialized pollutant transport and\narrangements were finalized at the\ndispersion forecasts be provided during\nWMO/CBS session in August 1994.\nthese emergencies.\nRecently, a fifth RSMC has been set up, in\nIn 1989, Regional Specialized Meteorology\nMelbourne, Australia, to provide products\nCenters at Toulouse, Bracknell and\nfor Region V (western Pacific). The\nMontréal were set up under interim\nMelbourne RSMC has been initiated using\narrangements between the WMO and the\nsome of the Washington (i.e. ARL)\nIAEA. Under these arrangements Meteo-\nprocedures and dispersion models. The\nFrance was to provide global coverage\nRSMCs in Washington and Montréal will\n(with Bracknell as the backup center) until\nprovide backup to Melbourne.\neach WMO region had at least two RSMCs\nfor transport model products.\nStructure.\nThe need for rationalization of transport\nThe RSMC Washington is a joint venture\nand dispersion forecasts became even more\nbetween the NWS National Meteorological\napparent during the oil fire emergency after\nCenter (NMC) and the Air Resources\nthe Gulf War, when many organizations\nLaboratory, merging the forecast skills and\nprovided ground personnel with predictions\noperational capabilities at NMC with the\nof the smoke plume behavior. These\npollutant dispersion modeling and analysis\npredictions were often misleading; there\ncapabilities of ARL. In essence, NMC\nwas no existing and well-recognized\nprovides the 24 hour per day initial contact\nsystem to sort out the predictions from\npoint for assistance requests. In the event\nless experienced sources.\nof an accident, the NMC operational staff\nconnect to ARL's computer system, which\nIn November 1992, a demonstration of\nis continuously updated with NMC forecast\nNOAA's RSMC capabilities was made to\nmodel output fields. Customized transport\nthe WMO's Commission for Basic Systems\nand dispersion models would then be run.\n(CBS) during their Tenth Session.\nModel outputs would be distributed\n65","EMERGENCY PREPAREDNESS\nautomatically to predesignated country\nmodel differences are partly due to\ndifferences in meteorological model's\nrepresentatives.\nspatial resolution as well as the effects of\nAfter the initial response by NMC the\nthe Lagrangian or Eulerian methods used to\noperational responsibility would be\ncompute the pollutant dispersion.\ntransferred to ARL, which at that point\nPrediction differences will have to be\nmight modify the dispersion model\naddressed by emergency planners when\nproducts to more accurately reflect the\nconfronted by multiple model output\nconditions of the accident. The ARL\nproducts. Regional RSMCs (such as\nresponse capability to assist in the RSMC's\nWashington and Montréal) plan to issue\noperation has been developed through\nstatements on differences between their\nvarious automated systems processes that\nproducts.\nlink a telephone pager to a facsimile, E-\nmail, and GTS message center.\nNOAA AIR RESOURCES LABORATORY\nAVERAGE FROM 00Z 02 JUN TO 00Z 03 JUN (UTC)\n002\n#2\nJUN\nRSM\nFORECAST INITIALIZATION\nBy agreement with the Canadian\nMeteorological Center (CMC), RSMCs\nWashington and Montréal will respond\njointly to emergencies in their region of\nconcern, each sending products to\ncountries requesting assistance, as well as\nconsulting with each other regarding model\noutput differences, product interpretation,\nand uncertainty. Regular monthly tests are\nconducted with the CMC.\nRecently, a joint project was initiated\nAIR CONCENTRATION AT LEVEL 0442 M (/M3)\nbetween ARL and NMC to develop a more\nIX11.0E-12\n(=)1.0E-14\n1+11.0E-16\n(/)1.0E-18\noperational coupled meteorological-\n3.5E-12 MAXIMUM AT SOLID (0)\nDOTS ABOVE ZERO (..)\ndispersion model. Modifications are being\nmade to NMC's Regional Spectral Model\n(RSM) to permit its application over any\nregion of the globe. RSL model outputs\nwill be linked directly with ARL dispersion\nmodels.\nExample.\nThe standard model products to be\ndistributed include forecasts of trajectories,\nair concentrations, and deposition. The\nfollowing illustration shows the 24 h\naverage air concentrations, forecast for a\nhypothetical release (presumed to be near\nMontréal) using the meteorological forecast\ndata from the 40 km version of the RSM.\nThere is a continuing program intended to\nidentify occasions in which differences in\nRSMC predictions arise, and to find the\ncauses for these differences. Dispersion\n66","EMERGENCY PREPAREDNESS\nTHE VAFTAD MODEL\nVolcanic Ash Transport Forecasts To Protect Aviation Operations\nBackground.\ncalculates the location of the volcanic ash\ncloud from a column extending from the\nVolcanic ash presents a danger to air\nvolcano summit to the top of the plume.\ntraffic. Jet engines, in particular, are\nFor aviation operations, calculated ash air\nsusceptible to malfunction if operated in a\nconcentrations have been correlated with\nplume of volcanic ash. ARL is a partner in\nash clouds detected by satellite imagery for\na multi-institutional collaborative activity\ndefining the visual plume.\ndesigned to provide air traffic with\nwarnings of the presence of volcanic ash\nApplications during 1994.\nalong air routes. The other partners include\nthe FAA, USGS, NWS, and NESDIS.\nThe accompanying figure is an example 8-\npanel chart of the forecast visual ash\nThe VAFTAD Model.\ncloud, as routinely distributed over DIFAX.\nThe four panels in any column are for a\nAs part of its emergency preparedness\nsingle valid time after eruption. Individual\nactivities at Silver Spring, the Air\npanels are for layers useful to aviation\nResources Laboratory has developed a\noperations and are identified at the side of\nVolcanic Ash Forecast Transport and\nthe panel with layer top and bottom\nDispersion (VAFTAD) model for volcanic\nheights. Following aviation practice, flight\nhazards alerts. The VAFTAD model:\nlevels (FL) are reported in hundreds of feet.\nThe bottom panel is a composite layer,\nfocuses on aviation operations by\nfrom the surface to the top of the model.\nforecasting the visual ash cloud in both\nFor each column, the valid time is given.\ntime and space,\nVolcano emission information is given at\nthe lower left, along with the run\nis user run, at any time, connected\ndescription. Three such charts are\nthrough INTERNET to an ARL workstation,\nnormally produced and distributed,\nusing screen-prompted model input, and\nrepresenting different forecast periods.\nWhen viewed in sequence, the set gives an\nautomatically telephones facsimile\neasily visualized time dependent view of\noutput charts of the forecast ash cloud to\nthe forecast ash cloud.\npredesignated recipients; output is also\nmade available over weather information\nVAFTAD is continually available for\ndistribution systems.\nemergency response operations. The initial\nrun is typically completed within ten\nThe model is coupled in realtime with\nminutes; updated runs with the latest\nNational Meteorological Center (NMC)\nmeteorological information can be\nforecast meteorological fields and is\ncontinued for several days following an\ndesigned to serve all of North America\neruption. A continuing ARL verification\nusing a fine scale grid and the entire globe\nprogram for VAFTAD has included three\nusing a coarser scale grid. ARL updates\neruptions of Spurr in Alaska (June, August,\nand archives the NMC meteorological\nand September, 1992), eruptions of Rinjani\ninformation twice daily. VAFTAD\nin Indonesia (June and July 1994), and a\n67","EMERGENCY PREPAREDNESS\n24 hour eruption of Klyuchevskoi in\nwith satellite imagery have been most\nKamchatka, Russia (September 1994).\nencouraging.\nResults comparing model ash forecasts\nCHART\nHAIR\nFL550\nFL350\nin\nH\nFL350\nFL200\nID\n13.00\n10\nPL.200\nSURFACE\nVALID 13% 01 OCT 0.1 (ERUPTION 1-3411)\nVALID 06% 02 OCT 94 (ERUPTION + -36H\n1.0\nAir\n10\nN.\nFL550\nSURFACE\n(COMPOSITE)\nCHART I\nLOWER HALF\nFigure 1. An example of the VAFTAD forecast output, as distributed in the even of a volcanic\neruption.\n68","INTERNATIONAL\nA WMO/GAW SCIENCE ACTIVITY CENTER FOR THE AMERICAS\nBackground.\nhistoric leadership in studies of\nprecipitation chemistry and atmospheric\nRecent WMO meetings (and a flurry of\nradioactivity, and because of its recent role\nreports) have emphasized that the global\nin atmospheric turbidity, NOAA/ARL is the\nmonitoring of air and precipitation\nlead organization for setting up the\nchemistry is in sad shape. In particular,\nQA/SAC (Science Activity Center) for the\nthere has been no process by which the\nAmericas. The QA/SAC is operated by the\nquality of even the most basic\nState University of New York, at Albany.\nenvironmental measurements can be\nassured. Major problems arose in the\nThe prospect is exciting, because for the\noperations of so-called Regional Stations\nfirst time there exists an opportunity to put\n(measuring precipitation chemistry,\nin place rational and effective standard\natmospheric turbidity, and atmospheric\noperating procedures world-wide, before a\nparticle loadings, for example); the data\nnew generation of measurement programs\nreported by research-grade global\ncommences. It is not intended to interfere\natmospheric observatories have not been\nwith programs that are already working\nso widely criticized. A fresh start is now\nwell, but to extend the experience of these\nbeing made, with a new Global\nprograms to other topical areas that are\nAtmosphere Watch (GAW) forming the\ncurrently seen as being vulnerable.\nframework for a nested network of refined\nregional and global observing stations.\nInitial Activities.\nThis new network will subsume and\nreplace the BAPMON (Background Air\nThe WMO QA/SACs are established in\nPollution Monitoring Network) activity of\naccordance with general guidelines\nearlier decades. In essence, the Global\ndeveloped for WMO by a panel of experts\nAtmosphere Watch is a coordinated system\n(WMO GAW Report No. 80). A second\nof networks of observing stations,\nmeeting of experts developed a set of\nfacilities, and arrangements, encompassing\nspecific guidelines and recommendations\nthe many measurement programs devoted\nfor the functions and implementation of\nto the investigation of the changing global\nthese QA/SACS.\natmosphere.\nIt was initially estimated that a credible\nA central goal of this activity is to permit\nactivity would require an annual budget of\ndata from individual national monitoring\nabout $300k. At present, three U.S.\nnetworks to be combined seamlessly, to\nagencies are directly involved: EPA, DOE,\nprovide the basis for sound regional\nand NOAA. In the future, contributions\nenvironmental policy. To this end, a small\nfrom other sources will be sought.\nnumber (three, or possibly four) of Quality\nAssurance Centers. One of these is to be\nPrecipitation chemistry, atmospheric\nsponsored by Germany (covering Europe\nradioactivity, and surface ozone were\nand Africa), and another by Japan\nidentified as subjects for immediate\n(covering Asia and Oceania). A provisional\nattention by the new QA/SAC (Americas).\ncommitment has been made by NOAA to\nIn each case, the initial focus for the\nlead in the setting up of a center to cover\nQA/SAC will be on designing quality\nthe Americas. This is among the highest\ncontrol procedures for aligning relevant\npriority of all activities currently being\ndata collected at stations in the Americas,\npromoted by the WMO. Because of its\nand on implementing quality assurance\n69","INTERNATIONAL\nsteps leading to an archiving function. It is\nAssurance of parsimony. Care must\nintended that topics being addressed by the\nbe taken to guard against unwarranted or\nQA/SAC (Americas) will be expanded as\nunnecessary attention to detail in any\nthe program continues.\nspecific area of concern. A balanced\nmeasurement program is desired, without\nInteractions with Data Centers.\nany part being of unacceptably low or\nunnecessarily high quality. Efforts to\nThe QA/SACs are an integral part of a\ncontinually improve data quality should be\ntripartite structure - GAW sites, QA/SACS\nmoderated by consideration of why the\nand Data Centers. The activities of the\ndata are being obtained.\nQA/SACs are loosely divided into\n\"network-wide\" and \"center-specific\"\nb) Center-specific\ntasks. The \"center-specific\" tasks can\nagain be subdivided into those associated\nFrom the communications point of view,\nprimarily with data flow, those associated\nthe most important aspect of data flow is\nprimarily with quality assurance support,\nthe development of methodologies to\nand those designed to ensure affective\nfacilitate the uninterrupted and reliable\ncommunication and dissemination of\nrecording and transfer of data from the\ninformation between the various partners.\nsite, through the QA/SAC, to the data\ncenter. This includes:\na) Network-wide\nDefining and reaching agreement on a\nNetwork-wide activities are related to the\nstandardized data format;\noperations of the QA/SACs, which are\nconceived as forming a closely linked\nDeveloping (identifying within the\nstructure with minimum duplication and\nnetwork) archiving software for recording\nclose coordination of activities. Many of\nof data, which can be made available to\nthe activities are much the same in all\nsites;\ncenters, but focused on a different group\nof sites. A system will be developed for\nDeveloping software for testing the\nclose coordination and networking between\nacceptability of data sets and repackaging\ncenters. Thus responsibility should be\ndata into component parts for transfer to\nallocated for the following activities:\nthe data centers;\nGeneral networking and information\nDeveloping a schedule for transfer of\nexchange. All the information described\ndata.\nunder the center-specific functions must be\npassed on to the other QA/SACS to ensure\nQuality assurance support activities\nmaximum benefit to all network\ninclude:\nparticipants. In many cases joint activities\n(workshops, newsletter, etc.) will be more\nDeveloping the schedule for quality\nappropriate than single-center activities.\ncontrol activities (site visits, performance\nand systems-audits, etc.).\nAvoidance of duplication. Procedures\nshould be developed to ensure mutual\nDesigning and conducting of\ncoordination of all development activities\nexperiments, either to resolve discrepancies\nand to minimize duplication across the\nobserved during review of data from\nnetwork.\nindividual sites, or in response to a request\n70","INTERNATIONAL\nfrom a data center (to resolve\nThe WMO Executive Council\ndiscrepancies between data and different\nPanel/CASWG on Environmental Pollution\nregions).\nand Atmospheric Chemistry (EC Panel).\nThe specification and prioritization of\nPromoting close links between sites\nscience and science policy driven\nwith more experience in the type of\nobjectives will be developed under the\nmeasurements required, and those where\nguidance of the WMO EC panel and with\nincreased training is desirable. (Such\nthe support of the QA/SACs.\ntwinning arrangements are likely to be the\nmost effective means of ensuring rapid\nInternational Scientific Programs in\nupgrading of all measurements in the\nAtmospheric Chemistry and Aerosols. At\nnetwork to the same high standard.)\npresent primary examples of these\nprograms include the International Global\nReviewing site locations periodically,\nAtmospheric Chemistry (IGAC) Program\n(a) to ensure that the locations are\nand the International Geosphere Biosphere\nsufficient to meet the requirements for any\nProgram (IGBP).\nnew scientific objectives included in the\nprogram, and b) to identify possible gaps\nScience and Technology Advisory\nresulting from fundamental changes in site\nPanel. In addition, to enhance interactions\nlocations identified during routine quality\nbetween the QA/SACs and the scientific\nassurance checks.\ncommunity, each QA/SAC has a Science\nand Technical Advisory Panel (STAP) to\nAllotting station performance ratings\nprovide advice on matters concerned with\naccording to well-defined definitions, and\nsite selection, instrumentation selection,\nrecommending removal of a station from\ninstrument calibration, auditing procedures,\nthe network if data are continually found to\netc.\nbe of poor quality.\nDeveloping procedures for raising\nawareness of technological changes and\nensuring efficient technology transfer\nwithin the network.\nConducting instrument comparison\nworkshops, and promoting improvements\nin instrumentation.\nEstablishing research ties with those\nmembers of the scientific community who\nare potential users of the GAW data.\nProgram Oversight.\nThe QA/SACS are planned to receive\ndirection and advice from the scientific\ncommunity and interact with it through\nthree formal mechanisms:\n71","","INTERNATIONAL\nINTERNATIONAL ACTIVITIES\nCollaborations with Foreign Scientists\nBackground.\nPlant Authority and the Atomic Energy\nAuthority. Support from FRD continued\nARL participates in a number of\nthrough 1994.\ninternational collaborations, as required to\naccomplish its mission and as appropriate\nEastern Europe.\nto further related scientific research. ARL\npolicy is governed by the recognition that\nAn extensive activity was begun, to\nthe air quality of the United States is\nimprove eastern European programs now\nslowly improving, in response to regulatory\nmeasuring wet deposition and to work\nactions and emission controls, while that of\ntowards a coordinated U.S.-style dry\nother parts of the world continues to\ndeposition program. In Poland, efforts are\ndeteriorate. The atmospheric environment\nunderway to establish two stations (near-\nof North America will doubtlessly become\nurban and background) that will meet\nincreasingly susceptible to emissions from\nWestern quality assurance objectives. In\nlocations over which the United States can\nthe Czech Republic, the wet and dry\nexert no direct control. It is the goal of\ndeposition monitoring station established in\nARL international activities, therefore,\n1993 at Rudolicze is now fully operational.\nARL has also participated in exploratory\nto monitor such aspects of the global\nstudies in Hungary.\natmospheric environment so as to reveal\nthe response of the atmosphere to changes\nOther eastern European countries are less\nin emissions in distant places,\nadvanced. To ensure that a common\nmessage was heard by all of the emerging\nto construct integrated models capable\ncountries in eastern Europe, a workshop\nof predicting future changes, and to\nwas held in December, in Garmisch-\nquantify the effects of these changes on\nPartenkirchen, Germany. The intent was to\nNorth America, and\nplan a long-term comprehensive deposition\nnetwork for Central and Eastern Europe, in\nto encourage the development of local\ncollaboration with the existing European\ncapabilities to provide relevant data.\nEMEP program and with the WMO's Global\nAtmosphere Watch. Ten countries from\nThe research component of these activities\nEastern and Central Europe participated.\nis viewed as an extension of the research\nprograms now under way in the U.S. A\nAustralia.\ncontrolling consideration is the need to\ndetect the effects of changes in emissions,\nThe ATDD-designed open-path infrared gas\nwith demonstrable confidence, as soon as\nanalyzer (IRGA) has proved to be widely\npossible.\npopular among the flux-measuring CO2\nresearch community. Seven of the\nEgypt.\ninstruments are now in use in Australia and\nNew Zealand. Personnel from ATDD fitted\nThe Field Research Division, Idaho Falls,\nIRGAs to Flinders University's Cessna 340\nhas been participating in a site-assessment\nand their Grob motor-glider. Tests of\nmodel development program at El Dabba,\npossible water valor contamination were\nEgypt, with the Egyptian Nuclear Power\nconducted at CSIRO/DEM in Canberra, also\n73","INTERNATIONAL\nMeasurement Methodology. During 1994,\nduring 1994. (The ATDD IRGA had\na working group meeting was held in St.\nnegligible contamination.)\nPetersburg. Additional meetings explored\nthe two operative bilateral agreements, the\nItaly.\n1972 Nixon/Podgorny and the 1993\nATDD has been working with the\nGore/Chernomyrdin agreements.\nNo\ndecision was made on which of these\nUniversity of Tuscia (Italy), on the setting\nmight subsume the other, but the same\nup of an international network to monitor\nscientists appear to be involved in both.\nCO2 fluxes over terrestrial ecosystems. An\ninaugural workshop was held, in December.\nA cooperative project with the Moscow\nThe goal was to establish an ad hoc global\nPhysics Institute was commenced, to study\nnetwork to directly address the issue of the\nKrypton-85 in the atmosphere. Kr-85 is a\nmissing sink in the global carbon balance.\nbyproduct of nuclear fission that could\npossibly disrupt natural atmospheric\nChina.\nelectrical fields.\nField tests of the rotating shadow band\napproach to atmospheric turbidity\nMexico.\nmeasurement are being conducted at sites\nWith the signing of the NAFTA treaty, a\nin China, in cooperation with the WMO\nnew emphasis is being placed on linkages\nGlobal Atmosphere Watch.\nwith Mexican environmental scientists.\nNew Zealand.\nNAFTA.\nThe New Zealand meteorological service is\nARL has participated in discussions on the\nnow an operational VAFTAD user.\nenvironmental aspects of the North\nAmerican Free Trade Agreement. Tom\nSpain and South Africa.\nWatson (FRD, Idaho Falls) attended the\nNAFTA Quality Assurance organizational\nThe ARL Dry Deposition Inferential Method\nmeeting, held in Queretaro, Mexico during\nfor evaluating dry deposition continues to\nNovember. The purpose of the meeting\nreceive favorable attention. The latest\nwas to start forming an organization which\ncountries to settle on the DDIM approach\nwill ensure that the environmental\nhave been South Africa and Spain.\nmeasurements made in the three NAFTA\ncountries are comparable.\nCanada.\nLester Machta was the long-time Chairman\nNATO.\nof the Air Quality Advisory Board of the\nThe North Atlantic Treaty Organization\nInternational Joint Commission. Lester\nstepped down in late 1993, and ARL is\nCommittee on Challenges on Modern\nSociety (NATO/CCMS) was established in\nnow represented on the Board by Rick Artz\n1969 to improve communications among\nof Silver Spring.\nmember countries on the task of providing\na better environment. ARL provides the\nRussia.\nU.S. representation on the CCMS Pilot\nStudy on Urban Pollutant Dispersion near\nARL provides the Chairmanship (Frank\nCoastal Areas and the CCMS Scientific\nSchiermeier, ASMD) of the U.S./Russia\nCommittee for International Technical\nWorking Group 02.01 on Air Pollution\nMeetings (Frank Schiermeier).\nModeling, Instrumentation, and\n74","ARL 1994 Publications\nBALDOCCHI, D.D. A comparative study of mass and energy exchange rates over a closed\nC3 (wheat) and an open C4 (corn) crop: II. CO, 2 exchange and water use efficiency.\nAgricultural and Forest Meteorology 67:291-321 (1994).\nBALDOCCHI, D.D. An analytical solution for coupled leaf photosynthesis and stomatal\nconductance models. Tree Physiology 14:1069-1079 (1994).\nBALDOCCHI, D.D., and S. Collineasu. The physical nature of solar radiation in heterogeneous\ncanopies: Spatial and temporal attributes. In Exploitation of Environmental Heterogeneity\nby Plants, M. Caldwell, and R. Pearcy (eds). Academic Press, Inc., San Diego, CA, 21-71\n(1994).\nBALDOCCHI, D.D. Are crops and forests spherical?: The role of canopy radiative transfer\nmodels on calculating canopy CO2 and energy exchange rates. Preprints, 21st\nConference on Agricultural and Forest Meteorology, San Diego, CA, March 7-11, 1994.\nAmerican Meteorological Society, Boston, 9-11 (1994).\nBENJEY, W.G. The spatial and source type distribution of emissions of selected toxic volatile\norganic compounds in the United States in 1990. In The Emission Inventory: Perception\nand Reality, VIP-38. Proceedings, International Specialty Conference, Pasadena, CA,\nOctober 1993. Air & Waste Management Association, Pittsburgh, 1033-1044 (1994).\nBowers, J.F., G.E. START, R.G. CARTER, T.B. WATSON, K.L. CLAWSON, and T.L.\nCRAWFORD. Experimental design and results for the Long-Range Overwater Diffusion\n(LROD) Experiment. Project Report DPG Document No. DPG/JCP-94/012, B. Grim,\nProject Manager, U.S. Army Dugway Proving Ground, Dugway, UT, 66 pp. + Appendices\n(1994).\nBULLOCK, O.R., JR. A computationally efficient method for the characterization of sub-grid-\nscale precipitation variability for sulfur wet removal estimates. Atmospheric Environment\n28:555-566 (1994).\nCLARK, T.L. Model assessment of the annual atmospheric deposition of trace metals to Lake\nSuperior. In ECE Co-Operative Programme for Monitoring and Evaluation of the Long-\nRange Transmission of Air Pollutants in Europe. Proceedings, The First Workshop on\nEmissions and Modeling of Atmospheric Transport of Persistent Organic Pollutants and\nHeavy Metals, Durham, North Carolina, May 1993. J.M. Pacyna, E. Voldner, G.J. Keeler\nand G. Evans (eds.), Norwegian Institute for Air Research, Norway, Environment Canada,\nUniversity of Michigan, and U.S. Environmental Protection Agency, 281-290 (1994).\nCohn, R.D., and R.L. DENNIS. The evaluation of acid deposition models using principal\ncomponent spaces. Atmospheric Environment 28:2531-2543 (1994).\nCOOTER, E.J., B.K. EDER, S.K. LEDUC, and L.E. TRUPPI. General Circulation Model output\nfor forest climate change research and applications. General Technical Report SE-85,\nU.S. Department of Agriculture, Forest Service, Southeastern Forest Experiment Station,\nAsheville, NC, 38 pp. (1994).\n75","COOTER, E.J., and S.K. LEDUC. Recent frost date trends in the northeastern United States.\nIn NOAA National Environmental Watch (CD-ROM) Prototype - 1994, Nathaniel Guttman\n(ed.). National Climatic Data Center, National Oceanic and Atmospheric Administration,\nAsheville, NC (1994).\nCOOTER, E.J., and S.K. LEDUC. Recent frost date trends in the northeastern United States.\nPreprints, Sixth Conference on Climate Variations, Nashville, TN, January 23-28, 1994.\nAmerican Meteorological Society, Boston, 178-181 (1994).\nCowherd, C., G.E. Muleski, J.S. Kinsey, J.S. TOUMA, and J.S. IRWIN. An intensive field\nstudy of air quality, meteorology and source activity at a western surface coal mine.\nProceedings, 87th Annual Meeting of the Air & Waste Management Association,\nCincinnati, OH, June 19-24, 1994. Air & Waste Management Association, Pittsburgh,\nPaper No. 94-FA145.03 (1994).\nCRESCENTI, G.H. Overview of PAMS meteorological monitoring requirements. Proceedings,\nMeasurement of Toxic and Related Air Pollutants, U.S. EPA/A&WMA International\nSymposium, Durham, NC, 245-253 (1994).\nCRESCENTI, G.H., B.D. TEMPLEMAN, AND J.E. Gaynor. Combining a monostatic sodar with\na radar wind profiler and RASS in a power plant pollution study. Proceedings, 7th\nInternational Symposium on Acoustic Remote Sensing, Boulder, CO, October 3-7, 1994,\n6-23 - 6-29 (1994).\nDaida, J.M., P.B. Russell, T.L. CRAWFORD, and J.F. Vesecky. An unmanned aircraft vehicle\nsystem for boundary-layer flux measurements over forest canopies. Preprints,\nInternational Geoscience and Remote Sensing Symposium '94, Pasadena, CA, (1994).\nDELUISI, J.J., C.L. Mateer, D. Theisen, P.K. Bhartia, D. Longenecker, and B. Chu. Northern\nmiddle-latitude ozone profile features and trends observed by SBUV and Umkehr, 1979-\n1990. Journal of Geophysical Research 99(D9):18,901-18,908 (1994).\nDENNIS, R.L., D.W. BYUN, and S.K. Seilkop. The influence of model design on comparisons\nof single point measurements with grid-model predictions. Preprints, Eighth Joint\nConference on Applications of Air Pollution Meteorology with A&WMA, Nashville, TN,\nJanuary 23-28, 1994. American Meteorological Society, Boston, 226-229 (1994).\nDENNIS, R.L., R.D. Cohn, and T. Odman. Oxidation of nitrogen: differences between\nmeasurements and predictions from the Regional Acid Deposition Model and whether grid\nsize can explain them. Preprints, Conference on Atmospheric Chemistry, Nashville, TN,\nJanuary 23-28, 1994. American Meteorological Society, Boston, 199-202 (1994).\nDRAXLER, R.R., J.T. MCQUEEN, and B.J.B. STUNDER. An evaluation of air pollutant\nexposures due to the 1991 Kuwait oil fires using a Lagrangian model. Atmospheric\nEnvironment 28(13):2197-2210 (1994).\nDUTTON, E., P. Reddy, S. Ryan, and J.J. DELUISI. Features and effects of aerosol optical\ndepth observed at Mauna Loa, Hawaii: 1982-1992. Journal of Geophysical Research\n99(D4):8295-8306 (1994).\n76","ECKMAN, R.M. Re-examination of empirically derived formulas for horizontal diffusion from\nsurface sources. Atmospheric Environment 28(2):265-272 (1994).\nEDER, B.K. An objective meteorological classification scheme designed to elucidate ozone's\ndependence on meteorology. Preprints, Eighth Joint Conference on Applications of Air\nPollution Meteorology with A&WMA, Nashville, TN, January 23-28, 1994. American\nMeteorological Society, Boston, 168-175 (1994).\nEDER, B.K. Non-urban ozone trends over the eastern United States. In NOAA National\nEnvironmental Watch (CD-ROM) Prototype - 1994, Nathaniel Guttman (ed.). National\nClimatic Data Center, National Oceanic and Atmospheric Administration, Asheville, NC\n(1994).\nEDER, B.K. On the feasibility of using satellite derived data to infer surface-layer ozone\nconcentration patterns. EPA/600/SR-94/081, Atmospheric Research and Exposure\nAssessment Laboratory, Research Triangle Park, NC (1994).\nELLIOTT, W.P., D.J. GAFFEN, J.D.W. Kahl, and J.K. ANGELL. The effect of moisture on\nlayer thicknesses used to monitor global temperatures. Journal of Climate 7(2):304-308\n(1994).\nGAFFEN, D.J. Effects of changes in radiosonde instruments and practices on climatological\nupper-air temperature records. Proceedings, WMO Technical Conference on Instruments\nand Methods of Observation (TECO-94), Geneva, Switzerland, 28 February - 2 March\n1994. Instruments and Observing Methods Report No. 57, WMO/TD 588 (1994).\nGAFFEN, D.J. Temporal inhomogeneities in radiosonde temperature records. Preprints, Sixth\nConference on Climate Variations, Nashville, TN, January 23-28, 1994. American\nMeteorological Society, Boston, 110-113 (1994).\nGAFFEN, D.J. Temporal inhomogeneities in radiosonde temperature records. Journal of\nGeophysical Research 99(D2):3667-3676 (1994).\nGalloway, J.N., J.M. Prospero, H. Rodhe, R.S. ARTZ, C.S. Atherton, Y.J., Balkanski, H.G.\nBingemer, R.A. Brost, S. Burgermeister, G.R. Carmichael, J.S. Chang, R.J. Charlson, S.\nCober, W.G. Ellis, Jr., C.J. Fischer, J.M. Hales, D.R. Hastie, T. Iversen, D.J. Jacob, K.\nJohn, J.E. Johnson, P.S. Kasibhatla, J. Langner, J. Lelieveld, H. Levy, II, F. Lipschultz,\nJ.T. Merrill, A.F. Michaels, J.M. Miller, J.L. Moody, J.E. Penner, J. Pinto, A.A.P. Pszenny,\nP.A. Spito, L. Tarrason, S.M. Turner, and D.M. Whelpdale. Sulfur and nitrogen cycling\nin the North Atlantic Ocean's atmosphere synthesis of field and modeling results. 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