A parameterization of cloud microphysics for long-term cloud-resolving modeling of tropical convection

Abstract

This paper documents development of a simple cloud microphysical parameterization for use in long-term cloud-resolving simulations of maritime tropical convection. The parameterization is based on the bulk approach and considers two classes of liquid water (cloud water and rain) and two classes of ice (slowly falling ice A and fast-falling ice B). Ice A represents unrimed or lightly rimed ice particles whose spectral characteristics are assumed to follow aircraft observations in tropical upper-tropospheric anvil clouds. Ice B, on the other hand, represents heavily rimed ice particles (e.g., graupel) which occur in the vicinity of convective towers. Mixing ratios for these four classes of cloud condensate are used as model variables. Together with the mixing ratio for water vapor, five field variables are used to represent all forms of water in the tropical atmosphere. The parameterization is used in a prescribed flow model to illustrate development of tropical convective and stratiform precipitation. Application of the parameterization to the cloud-resolving simulations of cloud systems observed during the TOGA COARE field campaign is also presented.