A Physically Based Subgrid Parameterization for the Production and Maintenance of Mixed-Phase Clouds in a General Circulation Model

摘要

A physically based method for parametrizing the role of subgrid scale turbulence in the production and maintenance of supercooled liquid water and mixed-phase clouds is presented. The approach used is to simplify the dynamics of supersaturation fluctuations to a stochastic differential equation that can be solved analytically, giving increments to the prognostic liquid cloud fraction and liquid water content fields in a General Circulation Model (GCM). Elsewhere, it has been demonstrated that the approach captures the properties of decameter-resolution Large Eddy Simulations of a turbulent mixed-phase environment. In this paper it is shown that it can be implemented in a GCM and the effects that this has on Southern Ocean biases and on Arctic stratus are investigated.