Atmos. Chem. Phys. Discuss., 12, 93-128, 2012
www.atmos-chem-phys-discuss.net/12/93/2012/
doi:10.5194/acpd-12-93-2012
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Regional and global modelling of aerosol optical properties with a size, composition, and mixing state resolved particle microphysics model
F. Yu, G. Luo, and X. Ma
Atmospheric Sciences Research Center, State University of New York, 251 Fuller Road, Albany, New York 12203, USA

Abstract. There exist large uncertainties in the present modelling of physical, chemical, and optical properties of atmospheric particles. We have recently incorporated an advanced particle microphysics (APM) model into a global chemistry transport model (GEOS-Chem) and a regional weather forecasting and chemistry model (WRF-Chem). Here we develop a scheme for calculating regional and global aerosol optical depth (AOD) from detailed aerosol information resolved by the APM model. According to GEOS-Chem-APM simulations, secondary species reside mainly as secondary particles (60–90%) in most parts of the globe, but in certain regions a large fraction (up to 50–80%) can become coated on various primary particles. Secondary species coated on black carbon and primary organic carbon particles significantly increase the size and hygroscopicity of these particles and thus impact their optical properties. The GEOS-Chem-APM model captures the global spatial distributions of AOD derived from AERONET, MODIS, and MISR measurements, generally within a factor of ~2. Our analysis indicates that modeled annual mean AODs at all sky and clear sky conditions differ by ~20% globally averaged and by >50% in some regions. A comparison of the time series of WRF-Chem-APM predicted AOD over the northeastern United States in June 2008 with those from seven AERONET sites shows that, overall, the model captures the absolute values as well as the variations of AOD at the AERONET sites (including dramatic changes associated with the crossing of high AOD plumes), although substantial differences exist during some periods. Both GEOS-Chem and WRF-Chem simulations indicate that AOD over the northeastern US is dominated by secondary particles and have large spatiotemporal variations.

Citation: Yu, F., Luo, G., and Ma, X.: Regional and global modelling of aerosol optical properties with a size, composition, and mixing state resolved particle microphysics model, Atmos. Chem. Phys. Discuss., 12, 93-128, doi:10.5194/acpd-12-93-2012, 2012.
 
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