The GRIST single-column model and its application in evaluating two physics parameterization packages

The single-column model of the Global-Regional Integrated forecast SysTem (GRIST_SCM) is introduced. GRIST_SCM simplifies the atmospheric dynamics within a single atmospheric column and enables relatively independent testing and evaluation of physical parameterizations. Two physics packages used for weather forecast (PhysW) and climate modeling (PhysC) are tested via GRIST_SCM. The Tropical Warm Pool International Cloud Experiment (TWP-ICE) is employed to study the representation of a deep convective process by PhysW and PhysC, respectively. Interactions among physical processes in terms of modeling clouds and precipitation are evaluated. Overall, cloud and precipitation evolution trends in the PhysW and PhysC simulations are consistent with observations. PhysW shows a better ability to simulate precipitation processes, while PhysC shows a better ability to simulate cloud processes. PhysC cannot well capture the onset and retreat of rainfall events during TWP-ICE. It produces persistent weak convective precipitation due to the too frequently triggered deep convection. The warm cloud fraction for PhysW is smaller than observations and that for PhysC. This is attributed to strong vertical transport of low-level water vapor by deep convective process, which leads to evaporation domination in the large-scale condensation/evaporation diagnosis based on relative humidity.