HR: 0800h
AN: A11C-0066    [Abstracts]
TI: Blending MODIS and AERONET Measurements for Monthly and Globally Varying Aerosol Size Distributions
AU: * Lesins, G
EM: glen.lesins@dal.ca
AF: Dalhousie University Department of Physics and Atmospheric Science, Dunn Building 6300 Coburg Road, Halifax, NS B3H 3J5 Canada
AU: Lohmann, U
EM: ulrike.lohmann@dal.ca
AF: Dalhousie University Department of Physics and Atmospheric Science, Dunn Building 6300 Coburg Road, Halifax, NS B3H 3J5 Canada
AB: The incorrect specification of atmospheric aerosol size can result in errors in the calculation of the aerosol optical thickness with subsequent errors in the direct radiative forcing. Furthermore model assessments of aerosol emissions using optical thickness for validation are difficult to perform if much of the error in optical thickness is caused by improper assumptions about the aerosol size distribution. To address these concerns the aerosol size distributions retrieved from 100 stations in the AERONET array of surface-based sun photometers are combined with the retrieved fine mode aerosol optical thickness fraction from MODIS-Terra to create a monthly climatology of a geographically varying vertically averaged aerosol size distribution. In this way the more detailed AERONET size distribution is blended with the excellent spatial and temporal coverage provided by MODIS for the four year period from March 2000 to February 2004. Various procedures for the specification of the aerosol size distribution are tested using the ECHAM4 climate model with the result that the global and annual averaged aerosol optical thickness at 500 nm is 0.17. However this value can vary from 0.11 to 0.20 depending on the method and assumptions used which translates into a direct aerosol TOA radiative forcing range of -1.6 to -3.9 W/m^2.
DE: 0305 Aerosols and particles (0345, 4801)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting