Preliminary results of a regional air-sea coupled model over East Asia

We have established a regional air-sea coupled model over East Asia and conducted a 20-year integration to evaluate its performance in reproducing the present climate. The coupled model consists of RegCM3 and HYCOM controlled by the OASIS3 coupler with resuolution of 60 km for the atmosphere and 33 km for the ocean, respectively. Unlike some other regional air-sea coupled models, a one-way nesting method is employed in the oceanic component and a heat flux adjustment for solar radiation is used to remove an about 2°C cold bias in SST. The primary analysis for this 20-year integration shows that the coupled model successfully reproduces the main features of the circulations over East Asia, both in the atmosphere and the ocean, including climatology, seasonal and interannual variations. Improvements are seen in the coupled model compared to the uncoupled one, especially in the simulation of precipitation, the most important element of the East Asian monsoon, although there are still obvious discrepancies that come mainly from the model components themselves. Further analyses show that the rainfall simulation benefits from the enhancements of the Northwest Pacific Subtropical High in summer, which leads to the improvement of the moisture flux simulation at the middle-lower atmospheric circulation. The results indicate that the regional air-sea coupled model is more suitable for the East Asia monsoon simulation.