Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 4 2008 10.5194/acpd-8-16027-2008 http://www.atmos-chem-phys-discuss.net/8/16027/2008/ http://www.atmos-chem-phys-discuss.net/8/16027/2008/acpd-8-16027-2008.html http://www.atmos-chem-phys-discuss.net/8/16027/2008/acpd-8-16027-2008.pdf 16027 16059 2008-08-22 Global error maps of aerosol optical properties: an error propagation analysis K. Tsigaridis ktsigaridis@giss.nasa.gov Y. Balkanski M. Schulz A. Benedetti Lab. des Sciences du Climat et de l'Environnement (LSCE), 91191 Gif-sur-Yvette, France European Center for Medium Range Weather Forecasts (ECMWF), Reading, UK now at: NASA Goddard Institute for Space Studies (GISS), 2880 Broadway, NY 10025, USA Among the numerous atmospheric constituents, aerosols play a unique role on climate, due to their scattering and absorbing capabilities, visibility degradation and their effect on incoming and outgoing radiation. The most important optical properties are the aerosol optical depth (AOD), the asymmetry parameter (<I>g</I>) and the single scattering albedo (SSA). Uncertainties in aerosol microphysics in global models, which in turn affect their optical properties, propagate to uncertainties on the effect of aerosols on climate. This study aims to estimate the uncertainty of AOD, <I>g</I> and SSA attributable to the aerosol representation in models, namely mixing state, aerosol size and aerosol associated water. As a reference, the monthly mean output of the general circulation model LMDz-INCA from the international comparison exercise AEROCOM B was used. For the optical properties calculations, aerosols were considered either externally mixed, homogeneously internally mixed or coated spheres. The radius was allowed to vary by &plusmn;20% (with 2% intervals) and the aerosol water content by &plusmn;50% (with 5% intervals) with respect to the reference model output. 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