Transferring the knowledge from ARM observations and CRM to improving GCM simulations of precipitation characteristics

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Description

The transfer of understanding of convection, cloud, and precipitation processes from ARM observations and CRM simulations to GCM is a challenging but important task. The combination of a CRM approach with ARM observations has gained knowledge in physical processes associated with convection, cloud, and radiation. Recently, we incorporated five modifications, including the improved convection scheme (closure, trigger, and convective momentum transport), the mosaic treatment of subgrid cloud variability, and the cloud scheme, into ISUGCM, which is based on a version of NCAR GCM. The ten-year simulation shows great impacts of modified schemes on the diurnal cycle and frequency of precipitation, seasonal migration of ITCZ, and MJO, which are closer to available observations. The observed diurnal cycles of precipitation over the central U.S. and the southeast U.S. are nicely reproduced by the ten-year GCM simulations for the first time. The inclusion of subgrid cloud variability in the radiation calculation allows the simulated cloud (liquid and ice) water paths and the TOA radiative fluxes to agree with the observations simultaneously. The comparison between ISUGCM and NCAR CAM4 will be presented to illustrate the importance of consistent treatment of convection, cloud, and radiation processes in the climate simulations.