摘要
Based on the 500-hPa geopotential height, surface air temperature, and China summer rain-belt type data from 1978 to 2002, the spatial spectrum function sets which well represent the variation of large scale atmospheric circulations were obtained using the least square method. A mechanism for the interannual variation of the East Asia-Pacific teleconnection （EAP） wave train in early summer was identified with the low-order spectral method and the hypothesis-test method. The results indicate that, when nonlinear wave- wave and wave-flow interactions on large scale are stronger in the inner dynamic process of the atmosphere, there are obvious nonlinear features in the evolution of the atmospheric circulation, and the EAP exhibits a negative-positive-negative （＂- ＋ -＂） spatial distribution in low to high latitudes in early summer. The corresponding EAP index is positive, which leads to a northward shift of the western Pacific subtropical high （WPSH） and the China rain-belt is located in the Huaihe River valley and its north in summer. On the contrary, when nonlinear wave-wave and wave-flow interactions on large scale are weaker, there appears a linear feature in the evolution of the atmospheric circulation, and the EAP shows a positive-negative-positive （＂＋ - ＋＂） spatial distribution in low to high latitudes. The corresponding EAP index is negative, which inhibits the WPSH against moving northward, and the China rain-belt is located in the Huaihe and Yangtze River valleys and their south.
Based on the 500-hPa geopotential height, surface air temperature, and China summer rain-belt type data from 1978 to 2002, the spatial spectrum function sets which well represent the variation of large scale atmospheric circulations were obtained using the least square method. A mechanism for the interannual variation of the East Asia-Pacific teleconnection （EAP） wave train in early summer was identified with the low-order spectral method and the hypothesis-test method. The results indicate that, when nonlinear wave- wave and wave-flow interactions on large scale are stronger in the inner dynamic process of the atmosphere, there are obvious nonlinear features in the evolution of the atmospheric circulation, and the EAP exhibits a negative-positive-negative （＂- ＋ -＂） spatial distribution in low to high latitudes in early summer. The corresponding EAP index is positive, which leads to a northward shift of the western Pacific subtropical high （WPSH） and the China rain-belt is located in the Huaihe River valley and its north in summer. On the contrary, when nonlinear wave-wave and wave-flow interactions on large scale are weaker, there appears a linear feature in the evolution of the atmospheric circulation, and the EAP shows a positive-negative-positive （＂＋ - ＋＂） spatial distribution in low to high latitudes. The corresponding EAP index is negative, which inhibits the WPSH against moving northward, and the China rain-belt is located in the Huaihe and Yangtze River valleys and their south.
基金
the National Natural Science Foundation of China under Grant Nos.40875054 and U0933603
the Natural Science Foundation of Yunnan Province under Grant No.2009CC002.
