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| Titel |
Aerosol impacts on California winter clouds and precipitation during CalWater 2011: local pollution versus long-range transported dust |
| VerfasserIn |
J. Fan, L. R. Leung, P. J. DeMott, J. M. Comstock, B. Singh, D. Rosenfeld, J. M. Tomlinson, A. White, K. A. Prather, P. Minnis, J. K. Ayers, Q. Min |
| 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. 1 ; Nr. 14, no. 1 (2014-01-03), S.81-101 |
| Datensatznummer |
250118244
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| Publikation (Nr.) |
 copernicus.org/acp-14-81-2014.pdf |
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| Zusammenfassung |
| Mineral dust aerosols often observed over California in winter and spring,
associated with long-range transport from Asia and the Sahara, have been
linked to enhanced precipitation based on observations. Local anthropogenic
pollution, on the other hand, was shown in previous observational and
modeling studies to reduce precipitation. Here we incorporate recent
developments in ice nucleation parameterizations to link aerosols with ice
crystal formation in a spectral-bin cloud microphysical model coupled with
the Weather Research and Forecasting (WRF) model in order to examine the
relative and combined impacts of dust and local pollution particles on cloud
properties and precipitation type and intensity. Simulations are carried out
for two cloud cases (from the CalWater 2011 field campaign) with contrasting
meteorology and cloud dynamics that occurred on 16 February (FEB16) and 2
March (MAR02). In both cases, observations show the presence of dust and
biological particles in a relative pristine environment. The simulated cloud
microphysical properties and precipitation show reasonable agreement with
aircraft and surface measurements. Model sensitivity experiments indicate
that in the pristine environment, the dust and biological aerosol layers
increase the accumulated precipitation by 10–20% from the Central Valley
to the Sierra Nevada for both FEB16 and MAR02 due to a ~40% increase
in snow formation, validating the observational hypothesis. Model results
show that local pollution increases precipitation over the windward slope of
the mountains by a few percent due to increased snow formation when dust is
present, but reduces precipitation by 5–8% if dust is removed on FEB16.
The effects of local pollution on cloud microphysics and precipitation
strongly depend on meteorology, including cloud dynamics and the strength of
the Sierra Barrier Jet. This study further underscores the importance of the
interactions between local pollution, dust, and environmental conditions for
assessing aerosol effects on cold-season precipitation in California. |
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