Open AccessModeled optical thickness of sea‐salt aerosol
Author(s) -
Madry William L.,
Toon Owen B.,
O'Dowd C. D.
Publication year - 2011
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010jd014691
Subject(s) - aerosol , sea salt , sea salt aerosol , aeronet , wind speed , environmental science , atmospheric sciences , optical depth , sea state , sea spray , mie scattering , angstrom exponent , satellite , meteorology , climatology , scattering , remote sensing , light scattering , geology , physics , optics , astronomy
We simulate the generation and microphysical evolution of sea‐salt aerosol using a climatologically driven 3‐D microphysical model for the year 2006. We then apply Mie theory to calculate the extinction and scattering efficiencies of our transported, size‐resolved sea‐salt aerosol, accounting for hygroscopic growth due to changes in ambient relative humidity. We calculate the column optical thickness of our modeled sea‐salt aerosol for comparison to three previously published wind speed–dependent clean marine air optical thickness formulations. Variously derived from optical thickness measurements and retrievals taken from the Midway Island AERONET site, the satellite‐based 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 sea‐salt 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 sea‐salt AOT, with only slightly diminished accuracy.