A Mechanism for the Interannual Variation of the Early Summer East Asia-Pacific Teleconnection Wave Train |
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| Authors: | YANG Ruowen TAO Yun CAO Jie |
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| Institution: | [1]Department of Atmospheric Sciences, Yunnan University, Kunming 650091 [2]Yunnan Institute of Meteorological Sciences, China Meteorological Administration, Kunming 650034 |
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| Abstract: | 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. |
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| Keywords: | East Asia-Pacific teleconnection wave train wave-wave interaction wave-flow interaction interannual variation anomaly |
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