资源环境科技发展态势分析平台

The present study investigates the intraseasonal wind variations over East Asia during boreal winter. It is shown that the wind variations less than 30 days are the main component of total intraseasonal signal. The intraseasonal variations in this time period are associated with two distinctive wave trains over Eurasia starting from the North Atlantic Ocean. One wave train propagates along the polar front jet eastward over Europe and Siberia and then southeastward after passing the Lake Baikal. The other wave train propagates along the subtropical jet southeastward through the Mediterranean region and the Arabian Peninsula to north India and then eastward to southern China. The East Asian wind and temperature anomalies are determined by the combination of the two wave trains. An anomalous cyclone forms over East Asia with large extent and intensity when the two wave trains work coherently, resulting in strong lower-level northerly wind anomalies with a large meridional extent. More cold air is transported southward from high latitudes by anomalous northerly winds, causing widespread and large temperature decrease in East Asia. When only a single wave train exists, lower-level wind and temperature anomalies are reduced. When there is a destructive interference of the two wave trains, the lower-level wind and temperature anomalies are weak in East Asia. Observational analyses and barotropic model experiments indicate that the formation of the two wave trains may be related to the combination of disturbances at different locations over the North Atlantic Ocean.