S.: Modeling impacts of mesoscale vertical motions upon coastal zone air pollution dispersion, Atmos

Abstract--This paper summarizes recent speculations on the impact of organized mesoscale vertical motions upon pollutant dispersion ear coastlines. Coastal zone phenomena, previously described from limited obsez vations and simple models are revisited using advanced meteorological nd dispersion models. A prognosti,: mesoscale meteorological model, when combined with a Lagrangian particle dispersion model, should more realistically simulate mesoscale dispersion than conventional Gaussian-plume odels in regions having strong vertical ascent and subsidence as well as wind shears, spatially variable mixing depths and recirculating wind fields. The fumigation of elevated plumes during onshore gradient flow is found to be influenced by even weak subsidence. Very fine mesh, three-dimensional simulations of sea breezes along both straight and complex shorelines suggest that sustained mesoscale frontal updrafts may be stronger than previously suspected, at times peaking in excess of 2 m s- t. Plumes released along the shoreline can be vertically translocated almost entirely out of the sea breeze inflow layer at the front. The hypothesis that plume trajectories tend to follow mesoscale, quasi-helical patterns i supported, but it is found that plume dispersion can at times be even more complex. Within sea breeze return flows, recirculating plumes may bifurcate into distinct branches with varying amounts of pollutants subsequently entrained back into the inflow layer. The numerical simulations suggest that for plumes containing aerosol