A coupled regional air-sea model, its performance and climate drift in simulation of the east Asian summer Monsoon in 1998

摘要

A regional climate model is coupled to a regional ocean model in this study, its performance in simulating the East Asian summer monsoon in 1998 is discussed, and the cold drift of the simulated sea-surface temperature (SST) that appears in the coupled model system and the reasons for its existence are found. The atmospheric component of the coupled model system is a regional climate model named P-sigma RCM, and the oceanic component of the coupled model is based on the Princeton ocean model (POM). By simulation-to-observation comparison, it is shown that the coupled model has a certain ability to simulate the seasonal propagation of the monsoon rain belt, the associated low-level southwest wind and the western Pacific subtropical high from May to August in 1998. It can reproduce the East Asian summer monsoon onset during the third dekad of May and its evolution process after the onset. From the coupled simulation results, it is also found that the south-to-north inflow in the southern South China Sea (SCS) and the summer monsoon current to the south of Sri Lanka do not occur until after mid-May, indicating that the ocean surface currents in the SCS and the Bay of Bengal regions are closely related with the SCS summer monsoon. The coupled simulation results show some differences with the individual uncoupled P-sigma RCM and POM. The obvious difference between the coupled and the uncoupled POM (also observation) is a cold tendency of simulated SST in the coupled model system. Two experimental groups are performed to investigate the reasons for the 'cold drift'. The results confirm that the 'cold drift' is mainly caused by the disagreement of the surface heat fluxes produced by the atmosphere model with those required by the POM. Therefore, a more accurate description and parameterization of the physical process in the atmosphere model is an important way to decrease the differences. Copyright 2005 Royal Meteorological Society.