The model will be run for periods of field measurement campaigns by the Atmospheric Chemistry Program and others, aiding both model evaluation and interpretation of controlling processes. This research will allow the accurate representation in climate models of forcing resulting from the scatter of solar radiation by anthropogenic aerosols. This forcing is estimated to be about 1 watt per square meter, global-annual average, but uncertain by a factor of 2. This uncertainty will be reduced by the parameterizations of aerosol mass loading and microphysical properties that will be developed by this research. The model distinguishes sulfate by formation mechanism and by geographical region of origin and source of material, anthropogenic or biogenic.
Anthropogenic sources are dominant through much of the model domain.
Substantial contribution due to sulfate imported into the model domain is indicated, necessitating extension of the model domain to the entire hemisphere. In FY98 we are extending the model domain to hemispheric, and will carry out model runs examining the influence of long range transport of sulfate into the present domain. We will conduct simulations of intensive field periods of international programs. Additionally we will develop and test representation of aerosol microphysics by the method of moments and will incorporate moment-based representation of aerosol dynamics into hemispheric scale model. We expect to participate in the formal model intercomparison studies under the aegis of the World Climate Research Project.