GLOBAL ATMOSPHERIC SEA-SALT DEPOSITION

• Main Author: ERICKSON, DAVID JULIUS
• Format: Text
• Language: English
• Published: DigitalCommons@URI 1987
• Subjects: Environmental science; Austral; North Atlantic
• Online Access: https://digitalcommons.uri.edu/dissertations/AAI8800138

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.)