| Project SageBrush phase 1 - :11188 | Office of Oceanic and Atmospheric Research (OAR)
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Project SageBrush phase 1
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Project SageBrush phase 1
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    The Field Research Division of the Air Resources Laboratory (ARLFRD) of the National Oceanic Atmospheric Administration (NOAA), in collaboration with the University of Tennessee Space Institute (UTSI) and the Laboratory for Atmospheric Research at Washington State University (WSULAR), conducted a tracer field experiment at the Idaho National Laboratory (INL) during October 2013. It is the first of a series of new tracer experiments to study dispersion from continuous sources in flat terrain using technologies not available during earlier dispersion studies of the 1950s and 1960s. These releases are collectively being called Project Sagebrush. The October 2013 study is designated Project SageBrush phase 1 (PSB1). Five tests were conducted during PSB1, all during the daytime with conditions ranging from near neutral with higher wind speeds to unstable with low wind speeds. Each experimental period consisted of a continuous 2.5 hours SF₆ tracer release with consecutive 10-minute average bag sampling over the last two hours of the tracer release period. Bag sampling was done on four arcs of almost 90 degrees each ranging in distance from 200 to 3200 m from the source, depending on the stability conditions and aircraft availability. The bag sampling measurements were complemented by six fast response tracer analyzers, an airborne fast response analyzer, and an extensive suite of meteorological measurements. This included a 60 m tower arrayed with seven 3-d sonic anemometers and five sets of cup anemometers and wind vanes. Two additional towers at 10 and 30 m height had cup and vane anemometers mounted at 2 and 3 levels, respectively. Three additional sonic anemometers were arrayed on the 3200 m arc to examine the issue of horizontal homogeneity. Additional meteorological measurements were made by two sodars, a radar wind profiler, and radiosondes released just prior to and just after the two hour sampling period. Preliminary analyses have identified some key results. The PSB1 results for the horizontal plume spread parameter ?y tended to be larger than the daytime ?y found in Project Prairie Grass and those determined from stability class model dispersion schemes (e.g., Pasquill- Gifford curves). The discrepancies increased with increasing downwind distance. However, the ?? and turbulence intensities measured during PSB1 were similar to those measured during the daytime in Project Prairie Grass. The result is that the PSB1 ratios of ?y/?? tended to fall near the upper limit or somewhat above the historical range of values found in previous field studies. Another key point is that the evidence suggests that ?y becomes independent of ? for ? greater than about 18 degrees. Finally, an investigation extending the comparison of ?? values into stable nighttime conditions found that the values of ?? reported during Project Prairie Grass and PSB1 differed significantly.[doi:10.7289/V5VX0DHV (http://dx.doi.org/10.7289/V5VX0DHV)]

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