Details:

Journal Title:
Atmospheric Chemistry and Physics
Personal Author:
Fiorella, Richard P. ; Bares, Ryan ; Lin, John C. ; Ehleringer, James R. ; Bowen, Gabriel J.
Fiorella, Richard P. ; Bares, Ryan ; Lin, John C. ; Ehleringer, James R. ; Bowen, Gabriel J. Less -
NOAA Program & Office:
OAR (Oceanic and Atmospheric Research) ; CPO (Climate Program Office)
OAR (Oceanic and Atmospheric Research) ; CPO (Climate Program Office) Less -
Description:
Water emitted during combustion may comprise a significant portion of ambient humidity (>  10 %) in urban areas, where combustion emissions are strongly focused in space and time. Stable water vapor isotopes can be used to apportion measured humidity values between atmospherically transported and combustion-derived water vapor, as combustion-derived vapor possesses an unusually negative deuterium excess value (d-excess, d  =  δ2H − 8δ18O). We investigated the relationship between the d-excess of atmospheric vapor, ambient CO2 concentrations, and atmospheric stability across four winters in Salt Lake City, Utah. We found a robust inverse relationship between CO2 excess above background and d-excess on sub-diurnal to seasonal timescales, which was most prominent during periods of strong atmospheric stability that occur during Salt Lake City winter. Using a Keeling-style mixing model approach, and assuming a molar ratio of H2O to CO2 in emissions of 1.5, we estimated the d-excess of combustion-derived vapor in Salt Lake City to be −179 ± 17 ‰, consistent with the upper limit of theoretical estimates. Based on this estimate, we calculate that vapor from fossil fuel combustion often represents 5–10 % of total urban humidity, with a maximum estimate of 16.7 %, consistent with prior estimates for Salt Lake City. Moreover, our analysis highlights that changes in the observed d-excess during periods of high atmospheric stability cannot be explained without a vapor source possessing a strongly negative d-excess value. Further refinements in this humidity apportionment method, most notably empirical validation of the d-excess of combustion vapor or improvements in the estimation of the background d-excess value in the absence of combustion, can yield more certain estimates of the impacts of fossil fuel combustion on urban humidity and meteorology.
Keywords:
[+]
Fossil fuels
Source:
Atmospheric Chemistry and Physics, 18, 8529–8547
DOI:
https://doi.org/10.5194/acp-18-8529-2018
Document Type:
Journal Article
Funding:
Grant no. NA14OAR4310178
Place as Subject:
Utah
Rights Information:
CC BY
Compliance:
Submitted
Main Document Checksum:
[+]
urn:sha256:8d82d0d038568d4e30bb0dfcb20547e4332c032064899306b695a3a6aab32fcf
Download URL:
https://repository.library.noaa.gov/view/noaa/24501/noaa_24501_DS1.pdf
File Type:

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