PARAMETERIZATION OF SUBGRID SCALE CONVECTIVE CLOUD TRANSPORT IN A MESOSCALE REGIONAL CHEMISTRY MODEL

A parameterization of subgrid scale convective cloud vertical mixing h as been developed in the National Oceanic and Atmospheric Administrati on Aeronomy Laboratory three-dimensional regional chemistry model. The parameterization is evaluated by comparing model results (with and wi thout the cloud mixing parameterization) with observations of O-3, NOx , and NOy made onboard the National Center for Atmospheric Research Sa breliner aircraft during the 1990 Rural Oxidants in the Southern Envir onment campaign in Alabama. Our studies show that model results with a nd without the cloud transport significantly differ from each other wh en convective clouds are present, implying that cloud exchange is an i mportant process in determining the distributions of trace species. Ou r studies also show that model results with the cloud transport parame terization are in much better agreement with the aircraft observations than those without.