GLOBAL ATMOSPHERIC SEA-SALT DEPOSITION

DAVID JULIUS ERICKSON, University of Rhode Island

Abstract

Seasonal estimates of sea-salt aerosol mass distributions 15 m above the sea are presented on global contour maps. Measured data from a variety of sources relating atmospheric sea-salt concentration to wind speed have been combined, yielding relationships of exponential form. These relationships, coupled with a Gaussian wind speed frequency distribution, allow us to calculate the atmospheric sea-salt concentration accounting for the variance about mean wind speeds. We use monthly wind mean speed and variance information in 5$\sp\circ$ x 5$\sp\circ$ latitude/longitude squares over the world ocean to estimate the global sea-salt aerosol particle mass distribution. The atmospheric sea-salt concentrations in the northern hemisphere marine troposphere display a substantial seasonal dependence. The three month seasonal average sea-salt concentrations in this region differ by a factor 2-3 between the boreal winter and summer, and the highest values are between 40 and 49 $\mu$g m$\sp{-3}$. The seasonal variability of atomspheric sea-salt concentrations in the high latitude southern hemisphere is much less than that in the northern hemisphere.^ Seasonal estimates of oceanic whitecap coverage are presented on global contour maps. The whitecap coverage in the northern hemisphere oceans displays a substantial seasonal dependence. The boreal summer average whitecap coverage in the high-latitude North Atlantic is about 0.5 percent. The whitecap coverage in the high-latitude southern hemisphere oceans exhibits only a factor of three difference for the same seasons, from about one percent in the austral summer to over three percent for the austral winter.^ The global wet and dry flux fields of atmospheric sea-salt to the ocean at 15 meters AMSL (Above Mean Sea Level) are examined on a monthly basis with the same spatial resolution as above. We estimate various global properties of atmospheric sea-salt, such as the mass-median radius of a log-normal sea-salt mass distribution, the deposition velocities of both wet and dry atmospheric sea-salt deposition and the global flux field of atmospheric sea-salt. The dry deposition of atmospheric sea-salt dominates wet deposition removal on a global scale. Over areas associated with the ITCZ (Inter Tropical Convergence Zone) atmospheric sea-salt is removed with comparable efficiency by both wet and dry deposition. (Abstract shortened with permission of author.) ^

Subject Area

Environmental Sciences

Recommended Citation

DAVID JULIUS ERICKSON, "GLOBAL ATMOSPHERIC SEA-SALT DEPOSITION" (1987). Dissertations and Master's Theses (Campus Access). Paper AAI8800138.
http://digitalcommons.uri.edu/dissertations/AAI8800138

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