Extending a dry‐environment convection parameterization to couple with moist turbulence and a baseline evaluation in the GRIST model

Abstract

This study presents an extension of a dry‐environment convection scheme (Tiedtke–Bechtold) to couple with a boundary‐layer moist turbulence scheme. The deep and shallow convective updraught is modified to develop in a moist environment and the large‐scale budget of cloud condensate takes account of the influence of compensation subsidence. An ambiguous layer is introduced in the sub‐cloud layer transport of shallow convection to mimic the non‐local transport that is ignored in the moist local turbulence scheme. Long‐term global simulation suggests that the modified convection and moist turbulence improve low cloud and short‐wave cloud radiative forcing. This includes a more realistic climatological structure of stratocumulus‐to‐cumulus transition and ameliorated biases in liquid water path. For short to mid‐term hindcasts in June 2021, the modified convection coupled with moist turbulence mitigates some regional over‐forecasts of precipitation. They improve the forecast ability for light and moderate precipitation. The modified model still retains the capability to capture the diurnal features of continental rainfall.