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| Titel |
Characterizing summertime chemical boundary conditions for airmasses entering the US West Coast |
| VerfasserIn |
G. G. Pfister, D. D. Parrish, H. Worden, L. K. Emmons, D. P. Edwards, C. Wiedinmyer, G. S. Diskin, G. Huey, S. J. Oltmans, V. Thouret, A. Weinheimer, A. Wisthaler |
| 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 ; 11, no. 4 ; Nr. 11, no. 4 (2011-02-25), S.1769-1790 |
| Datensatznummer |
250009377
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| Publikation (Nr.) |
 copernicus.org/acp-11-1769-2011.pdf |
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| Zusammenfassung |
| The objective of this study is to analyze the pollution inflow into
California during summertime and how it impacts surface air quality through
combined analysis of a suite of observations and global and regional models.
The focus is on the transpacific pollution transport investigated by the
NASA Arctic Research of the Composition of the Troposphere from Aircraft and
Satellites (ARCTAS) mission in June 2008. Additional observations include
satellite retrievals of carbon monoxide and ozone by the EOS Aura
Tropospheric Emissions Spectrometer (TES), aircraft measurements from the
MOZAIC program and ozonesondes. We compare chemical boundary conditions (BC)
from the MOZART-4 global model, which are commonly used in regional
simulations, with measured concentrations to quantify both the accuracy of
the model results and the variability in pollution inflow. Both observations
and model reflect a large variability in pollution inflow on temporal and
spatial scales, but the global model captures only about half of the
observed free tropospheric variability. Model tracer contributions show a
large contribution from Asian emissions in the inflow. Recirculation of
local US pollution can impact chemical BC, emphasizing the importance of
consistency between the global model simulations used for BC and the
regional model in terms of emissions, chemistry and transport. Aircraft
measurements in the free troposphere over California show similar
concentration ranges, variability and source contributions as free
tropospheric air masses over ocean, but caution has to be taken that local
pollution aloft is not misinterpreted as inflow. A flight route specifically
designed to sample boundary conditions during ARCTAS-CARB showed a
prevalence of plumes transported from Asia and thus may not be fully
representative for average inflow conditions. Sensitivity simulations with a
regional model with altered BCs show that the temporal variability in the
pollution inflow does impact modeled surface concentrations in California.
We suggest that time and space varying chemical boundary conditions from
global models provide useful input to regional models, but likely still lead
to an underestimate of peak surface concentrations and the variability
associated with long-range pollution transport. |
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