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| Titel |
Modeling regional aerosol and aerosol precursor variability over California and its sensitivity to emissions and long-range transport during the 2010 CalNex and CARES campaigns |
| VerfasserIn |
J. D. Fast, J. Allan, R. Bahreini, J. Craven, L. Emmons, R. Ferrare, P. L. Hayes, A. Hodzic, J. Holloway, C. Hostetler, J. L. Jimenez, H. Jonsson, S. Liu, Y. Liu, A. Metcalf, A. Middlebrook, J. Nowak, M. Pekour, A. Perring, L. Russell, A. Sedlacek, J. Seinfeld, A. Setyan, J. Shilling, M. Shrivastava, S. Springston, C. Song, R. Subramanian, J. W. Taylor, V. Vinoj, Q. Yang, R. A. Zaveri, Q. Zhang |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 18 ; Nr. 14, no. 18 (2014-09-22), S.10013-10060 |
| Datensatznummer |
250119055
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| Publikation (Nr.) |
 copernicus.org/acp-14-10013-2014.pdf |
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| Zusammenfassung |
| The performance of the Weather Research and Forecasting regional model with
chemistry (WRF-Chem) in simulating the spatial and temporal variations in
aerosol mass, composition, and size over California is quantified using the
extensive meteorological, trace gas, and aerosol measurements collected
during the California Nexus of Air Quality and Climate Experiment (CalNex)
and the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted
during May and June of 2010. The overall objective of the field campaigns
was to obtain data needed to better understand processes that affect both
climate and air quality, including emission assessments, transport and
chemical aging of aerosols, aerosol radiative effects. Simulations were
performed that examined the sensitivity of aerosol concentrations to
anthropogenic emissions and to long-range transport of aerosols into the
domain obtained from a global model. The configuration of WRF-Chem used in
this study is shown to reproduce the overall synoptic conditions,
thermally driven circulations, and boundary layer structure observed in
region that controls the transport and mixing of trace gases and aerosols.
Reducing the default emissions inventory by 50% led to an overall
improvement in many simulated trace gases and black carbon aerosol at most
sites and along most aircraft flight paths; however, simulated organic
aerosol was closer to observed when there were no adjustments to the primary
organic aerosol emissions. We found that sulfate was better simulated over
northern California whereas nitrate was better simulated over southern
California. While the overall spatial and temporal variability of aerosols
and their precursors were simulated reasonably well, we show cases where the
local transport of some aerosol plumes were either too slow or too fast,
which adversely affects the statistics quantifying the differences between
observed and simulated quantities. Comparisons with lidar and in situ
measurements indicate that long-range transport of aerosols from the global
model was likely too high in the free troposphere even though their
concentrations were relatively low. This bias led to an over-prediction in
aerosol optical depth by as much as a factor of 2 that offset the
under-predictions of boundary-layer extinction resulting primarily from
local emissions. Lowering the boundary conditions of aerosol concentrations
by 50% greatly reduced the bias in simulated aerosol optical depth for
all regions of California. This study shows that quantifying regional-scale
variations in aerosol radiative forcing and determining the relative role of
emissions from local and distant sources is challenging during `clean'
conditions and that a wide array of measurements are needed to ensure model
predictions are correct for the right reasons. In this regard, the combined
CalNex and CARES data sets are an ideal test bed that can be used to evaluate
aerosol models in great detail and develop improved treatments for aerosol
processes. |
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