CAM6 simulation of mean and extreme precipitation over Asia: sensitivity to upgraded physical parameterizations and higher horizontal resolution

Since CESM2-CAM6 will participate in the upcoming Coupled Model Intercomparison Project phase 6 (CMIP6) and is likely to be adopted in many future studies, its simulation fidelity needs to be thoroughly examined Here we evaluate the performance of a developmental version of the Community Atmosphere Model with parameterizations that will be used in version 6 (CAM6 alpha), with a default 1 degrees horizontal resolution (0.9 degrees x 1.25 degrees, CAM6 alpha-1 degrees) and a high-resolution configuration (approximately 0.25 degrees, CAM6 alpha-0.25 degrees), against various observational and reanalysis datasets of precipitation over Asia.

CAM6 alpha performance is compared with CAMS at default 1 degrees horizontal resolution (CAMS-1 degrees) and a high-resolution configuration at 0.25 degrees (CAM5-0.25 degrees). With the prognostic treatment of precipitation processes and the new microphysics module, CAM6 alpha is able to better simulate climatological mean and extreme precipitation over Asia, better capture the heaviest precipitation events, better reproduce the diurnal cycle of precipitation rates over most of Asia, and better simulate the probability density distributions of daily precipitation over Tibet, Korea, Japan and northern China.