Can coupled models perform better in the simulation of sub‐seasonal evolution of the western North Pacific subtropical high than atmospheric models in boreal summer?

Abstract

This study examines the climatological sub‐seasonal evolution of the western North Pacific subtropical high (WNPSH) in boreal summer using observation and multiple state‐of‐the‐art climate models, which has not been focused by previous research. The two sub‐seasonal shifts in boreal summer are analyzed, one from June to July (J–J) and another from July to August (J–A). In observation, the WNPSH consistently retreats eastward and jumps northward (weakens) from June to August. Driven by observed sea surface temperature (SST), the multi‐models ensemble (MME) of atmospheric general circulation models (AGCMs) that participated in the Coupled Model Intercomparison Project Phase 5 (CMIP5) can reproduce the weakening of WNPSH from June to July, but fail to simulate the weakening from July to August. This may be due to the sub‐seasonal variation of local SST increasing from June to July but decreasing from July to August. Compared with AGCMs simulation, CMIP5 coupled models MME largely improve the sub‐seasonal variation of the WNPSH and associated precipitation change. Thus, it is argued that coupled models should be adopted in studies of the WNPSH on sub‐seasonal timescales.