Impact of scale-aware deep convection on the cloud liquid and ice water paths and precipitation using the Model for Prediction Across Scales (MPAS-v5.2)

Abstract. The cloud Liquid Water Path (LWP), Ice Water Path (IWP), and precipitation simulated with uniform- and variable-resolution numerical experiments using the Model for Prediction Across Scales (MPAS) are compared against Clouds and the Earth’s Radiant Energy System (CERES) and Tropical Rainfall Measuring Mission data. Our comparison between monthly mean model diagnostics and satellite data focuses on the convective activity regions of the Tropical Pacific Ocean, extending from the Eastern Tropical Pacific Basin where trade wind boundary layer clouds develop to the Western Pacific warm pool defined by deep convective updrafts capped with extended upper-tropospheric ice clouds. Using the scale-aware Grell-Freitas (GF) and Multi-Scale Kain-Fritsch (MSKF) convection schemes with the Thompson cloud microphysics scheme, uniform-resolution experiments produce large biases between simulated and satellite-retrieved LWP, IWP, and precipitation. Differences in the treatment of shallow convection lead the LWP to be strongly overestimated when using GF while being in relatively good agreement when using MSKF compared to CERES data. Over areas of deep convection, numerical experiments using MSKF lead to increased IWP than those using GF, in conjunction with increased convective detrainment of cloud ice and ice nucleation. Mesh refinement over the Western Pacific warm pool yields increased grid-scale condensation, LWP, IWP, and cloudiness over the refined area of the mesh associated with increased grid-scale upward vertical motions. Results underscore the importance of evaluating clouds, their optical properties, and the top-of-the-atmosphere radiation budget in addition to precipitation when performing mesh refinement global simulations.