Sea Salt Aerosol Production: Parameterization and Uncertainty. Lewis E. R. and Schwartz S. E. American Geophysical Union Fall Meeting, San Francisco, December 13-17, 2004.

Based on a critical review (Lewis and Schwartz, 2004) of sea salt aerosol (SSA) properties and processes, field measurements of concentrations, and production fluxes estimated by a variety of methods, a parameterization is presented for the effective (10 m) size-dependent production flux of SSA particles for r80 (radius at 80% relative humidity) 0.1-25 Ám and U10 (10 m wind speed) 5-20 ms-1. This flux is given by a single lognormal of the form

dF/dlogr80/(m-2s-1) = 50[U10/(ms-1)]2.5 exp{-[log(r80/r80')/log(s)]2/2},


with r80' = 0.3 Ám and s = 4, and with associated multiplicative uncertainty of a factor of 4 to 5. At typical wind speed 10 ms-1, this formulation is less than that given by some commonly used parameterizations by up to a factor of 80. This production flux formulation is based on a size distribution of SSA concentration that encompasses the great majority of reported field measurements and can be represented over the same range of r80 and U10 by a single lognormal of the form

dN/dlogr80/(cm-3) = 0.07[U10/(ms-1)]2 exp{-[log(r80/r80')/log(s)]2/2},


with r80' = 0.3 mm and s = 2.8, and with associated multiplicative uncertainty of a factor of 3 reflecting variability resulting from factors other than wind speed. Based on this expression, the number concentration of SSA particles that function as CCN is a weak function of supersaturation, with more than 80% of SSA particles activating at supersaturations greater than 0.1%. The time characterizing uptake of reactive gases such as H2SO4 at wind speed 10 ms-1 is 0.15-1.5 h, implying a possible strong influence of SSA on nucleation suppression and aerosol evolution. The dominant contribution to light scattering by SSA particles is from particles having r80 1-10 Ám, implying that measurements that do not include SSA particles throughout this entire size range substantially underestimate the influence of SSA on light scattering and Earth's radiative balance.

Lewis E. R. and Schwartz S. E. Sea Salt Aerosol Production: Mechanisms, Methods, Measurements, and Models -- A Critical Review. Geophysical Monograph Series Vol. 152, (American Geophysical Union, Washington, 2004).


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