A mechanism for the interannual variation of East Asia-Pacific teleconnection wave train in early summer

Using 500 hPa height, surface air temperature and China summer rain belt type data from 1978 to 2002, 25 spatial spectrum function sets representing the variation of large scale atmospheric circulation were retrieved with the least square method. A mechanism for the interannual variation of the East Asia-Pacific teleconnection wave train in early summer was found through a low-order truncation spectral method and the statistical hypothesis test method. The results indicate that, when the large scale wave-wave and waveflow interactions are significant, there are obvious nonlinear features in the evolution of the atmospheric circulation, and the East Asia-Pacific teleconnection presents a “-,+,-” spatial distribution from low to high- latitudes in early summer. The corresponding index of the EAP is positive the western Pacific subtropical high shifts northward, and anomalous heavy rainfall occurs in the Huaihe Valley and its north in summer. On the contrary, when the large scale wave-wave and waveflow interactions are weak, there appear linear features in the evolution of the atmospheric circulation, the East Asia-Pacific teleconnection shows a “+,-,+” distribution from low-to high- latitudes. The corresponding index of EAP is negative, the western Pacific subtropical high does not move northward significantly, and anomalous heavy rain happens in the Yangtze and Huaihe River valleys and their south.