Impacts of SST Anomalies in Different Tropical Oceans on the Asian Summer Monsoon

The relationship between the sea surface temperature anomaly (SSTA) in different tropical oceans and the intensity of the Asian summer monsoon has been analyzed. To analyze the differences in air-sea interaction of different regions, the WRF model is used to understand the impacts of SSTAs in the South China Sea (SCS), the Bay of Bengal (BOB), and the Arabian Sea (AS) on the variations of tropical Asian summer monsoon circulation and precipitation. The result shows that warm SST in April generates anomalous latent heat flux, which influences the atmospheric circulation over the oceans. In three ocean domains, warm SST triggers cyclonic circulation anomaly, resulting in lower atmospheric convergence anomaly and upper atmospheric divergence anomaly. This pattern of atmospheric circulation favors intensifications of atmospheric convection and monsoon activity. The impact of warm SST in May is similar to that for April, but the negative effect on the convective activity over eastern China is different. In general, the warm SSTA in May is not conducive to northward propagation of SCS summer monsoon. According to the comparison of sensitive experiments, the impacts of SCS SSTA in April are most evident, and the impacts of BOB SSTA in May are most evident. Among the sensitivity experiments of April, warm SSTA of SCS favors the monsoon activities over AS, north of BOB and SCS; the positive anomaly of precipitation has wider range in BOB and AS. Among the sensitivity experiments of May, warm SSTA in SCS has less impacts on the westerly over tropic comparing to that in BOB; locally, the impacts of SSTA in BOB and AS are more evident than those of SCS SSTA.