Simulation of Climatology and Interannual Variability of Spring Persistent Rains by MRI Model: Comparison of Different Horizontal Resolutions

This study evaluated the performance of Meteorological Research Institute of Japan (MRI) atmospheric general circulation models (AGCMs) that participated in the Couple Model Intercomparison Project 5 (CMIP5), focusing on climatology and interannual variability of the Spring Persistent Rains (SPR) over southeastern China. Simulations of different horizontal resolutions (i.e., 120, 60, and 20 km) were also compared. The model could reasonably reproduce the main rainfall center over southeastern China in boreal spring under the three different resolutions. In comparison with the 120-km simulation, the simulation with 20-km resolution gave better results in simulating rainfall centers located in the Nanling-Wuyi Mountains, but overestimated rainfall intensity. Water vapor budget diagnosis showed that, both the 60 km and 20 km simulations tended to overestimate the water vapor convergence over southeastern China, which led to wet biases. With regard to interannual variability of SPR, the model could reasonably reproduce the anomalous lower-tropospheric anticyclone in the western North Pacific (WNPAC) and positive precipitation anomalies over southeastern China in the El Niño decaying spring. Compared with that of the 120-km simulation, the large positive biases were substantially reduced in the 60-km and 20-km resolution simulations because the horizontal moisture advection in El Niño decaying spring was more realistically simulated. The results highlight the importance of developing high resolution climate model for improving the simulation of climatology and interannual variability of SPR.