Numerical study on influence of anomaly of sea ice in the Weddell Sea on seasonal transition in East Asia during early summer

By employing the CCM1 (R15L7) model which was formed from NCAR'S CCM1 (R15L12) model by making some changes for being more suitable to the long-range numerical weather prediction, three numerical experiments-the climatic monthly mean ice boundary in the Weddell Sea (60°W~30°E),the maximum extent and the minimum extent of that-have been carried out to investigate the influence of ice boundary in Antarctica on the seasonal transition in the early summer in East Asia.The recults show that when sea ice boundary is at its maximum extent, the characteristics of circulation in East Asia are more like that in winter, the divergence of north and south westerly jet stream in East Asia is clear, and the activities of rnld air in North Asia are still active and their intensity is still strong.More ice in the Weddell Sea has no benefit to the seasonal transition in East Asia.When sea ire is at its minimum extent, on the contrary, the activities of cold air in North Asia are weakened, the warm-damp flow in South Asia becomes strong and moves more northward and the trend of confluence of two westerly jet stream-the northern one and the southern one-is more clear in East Asia, and the characteristics of circulation are favourable to advance the seasonal transition in East Asia.On the basis of model results, we conclude that ice margin anomalies in the Weddell Sea are capable of influencing the circulation and climate in East Asia.The anomalies of ice boundary will hinder or advance the seasonal transition in East Asia during the early summer.