Multiscale Simulation of Precipitation Over East Asia by Variable Resolution CAM‐MPAS.

This study evaluates the precipitation over East Asia simulated by the variable resolution CAM‐MPAS featuring the Model for Prediction Across Scales (MPAS) atmospheric dynamical core coupled with the physics parameterizations of the Community Atmosphere Model (CAM) version 5.4. Two CAM‐MPAS experiments, one with a global quasi‐uniform resolution mesh of 120 km (MPAS‐UR) and the other with a variable resolution mesh of 30–120 km refined over East Asia (MPAS‐VR), are conducted from 1989 to 2005 following the Atmospheric Model Intercomparison Project protocol. Two regional climate model simulations at ∼25 km resolution from the Coordinated Regional Downscaling Experiment East Asia second plan are also analyzed for comparison. Results show that CAM‐MPAS performs better than the selected regional models in simulating the precipitation climatology over East Asia. Compared with MPAS‐UR, MPAS‐VR with refinement over East Asia better simulates the precipitation over and around the Tibetan Plateau (TP), the upper‐level circulation, the precipitation frequency and intensity in various regions of China, and the interannual precipitation pattern associated with the East Asian summer monsoon. Both decreased grid spacing and the use of finer‐scale terrain information contribute to the improvements in MPAS‐VR relative to MPAS‐UR. However, decreased grid spacing is more essential for simulating the precipitation magnitude over TP and the location of peak precipitation south of TP, likely due to the better resolved physical and dynamical processes associated with orographic precipitation. The 30–120 km CAM‐MPAS model is shown to be a promising tool for precipitation simulation over East Asia. Plain Language Summary: Precipitation and associated cloud and radiation processes can affect the energy budgets and water supply over land and thus the livelihoods of billions of people over East Asia. However, traditional low‐resolution global climate models still have difficulty in realistically simulating the mean‐state and variability of precipitation over East Asia, partly due to their insufficient resolution to resolve the complex terrain and associated synoptic‐scale systems. In this work, we perform model experiments using the Community Atmosphere Model coupled with the atmospheric dynamical core from the Model for Prediction Across Scales with a variable resolution mesh to assess the impact of regional refinement on the precipitation simulation over East Asia. Experiment with higher resolution (30 vs. 120 km) over East Asia better simulates the total precipitation amount over and around the Tibetan Plateau (TP), as well as precipitation frequency, intensity, and interannual variability associated with the East Asian summer monsoon. The finer grid spacing is found to contribute more to the improvements in areas adjacent to TP than the use of finer terrain information, likely due to better resolved physical and dynamical processes associated with orographic precipitation. Key Points: The precipitation climatology over East Asia can be reasonably reproduced by a global climate model CAM‐MPASRegional refinement over East Asia improves the precipitation simulation over East Asia in various aspectsFiner grid spacing is more essential for precipitation simulation around large‐scale terrain than using finer‐scale terrain information [ABSTRACT FROM AUTHOR]