Details for Modeled Optical Thickness of the Sea Salt Aerosol Over the World Ocean

Name:Modeled Optical Thickness of the Sea Salt Aerosol Over the World Ocean

Madry, L.M., O.B. Toon, C. D. O’Dowd, Modeled Optical Thickness of the Sea Salt Aerosol Over the World Ocean, J. Geophys. Res. doi:10.1029/2010JD014691, 2011.

We simulate the generation and microphysical evolution of seas

alt aerosol using a climatologically driven 3D microphysical model for the year 2006. We then apply Mie theory to calculate the extinction and scattering efficiencies of our transported, sizeresolved seasalt aerosol, accounting for hygroscopic growth due to changes in ambient relative humidity. We calculate the column optical thickness of our modeled seasalt aerosol for comparison to three previously published wind speeddependent clean  marine air optical thickness formulations. Variously derived from optical thickness measurements and retrievals taken from the Midway Island AERONET site, the satellitebased MODIS instruments, and the Global Atmospheric Watch (GAW) site at Mace Head, Ireland, the three formulations report similar background levels of clean marine AOT at zero wind speed but significantly different functional dependencies for nonzero wind speeds. We find that our modeled seasalt aerosol optical thickness very closely depends on the square of surface wind speed under steady state conditions. This relationship is consistent across all latitudes. However, due to the fact that steady state winds are seldom maintained, the 24 h mean wind is more frequently applicable to calculations of seasalt AOT, with only slightly diminished accuracy.
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