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| Titel |
Technical Note: Evaluation of the WRF-Chem "Aerosol Chemical to Aerosol Optical Properties" Module using data from the MILAGRO campaign |
| VerfasserIn |
J. C. Barnard, J. D. Fast, G. Paredes-Miranda, W. P. Arnott, A. Laskin |
| 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 ; 10, no. 15 ; Nr. 10, no. 15 (2010-08-09), S.7325-7340 |
| Datensatznummer |
250008689
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| Publikation (Nr.) |
 copernicus.org/acp-10-7325-2010.pdf |
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| Zusammenfassung |
| A comparison between observed aerosol optical properties from the MILAGRO
field campaign, which took place in the Mexico City Metropolitan Area (MCMA)
during March 2006, and values simulated by the Weather Research and
Forecasting (WRF-Chem) model, reveals large differences. To help identify
the source of the discrepancies, data from the MILAGRO campaign are used to
evaluate the "aerosol chemical to aerosol optical properties" module
implemented in the full chemistry version of the WRF-Chem model. The
evaluation uses measurements of aerosol size distributions and chemical
properties obtained at the MILAGRO T1 site. These observations are fed to
the module, which makes predictions of various aerosol optical properties,
including the scattering coefficient, Bscat; the absorption coefficient,
Babs; and the single-scattering albedo, ϖ0; all as a function of
time. Values simulated by the module are compared with independent
measurements obtained from a photoacoustic spectrometer (PAS) at a
wavelength of 870 nm. Because of line losses and other factors, only "fine
mode" aerosols with aerodynamic diameters less than 2.5 μm are
considered here. Over a 10-day period, the simulations of hour-by-hour
variations of Bscat are not satisfactory, but simulations of Babs
and ϖ0 are considerably better. When averaged over the 10-day period,
the computed and observed optical properties agree within the uncertainty
limits of the measurements and simulations. Specifically, the observed and
calculated values are, respectively: (1) Bscat, 34.1±5.1 Mm−1
versus 30.4±3.4 Mm−1; (2) Babs, 9.7±1.0 Mm−1
versus 11.7±1.2 Mm−1; and (3) ϖ0, 0.78±0.05 and 0.74±0.03.
The discrepancies in values of ϖ0 simulated by the full
WRF-Chem model thus cannot be attributed to the "aerosol chemistry to
optics" module. The discrepancy is more likely due, in part, to poor
characterization of emissions near the T1 site, particularly black carbon
emissions. |
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