The Configuration Between The East Asia Pacific And The Eurasian Teleconnection Patterns And Their Influence On The Climate Of China

By using NCEP/NCAR reanalysis data and the precipitation data of stations in China, we examined two summertime teleconnection patterns, the East Asia Pacific (EAP) and the Eurasian (EU) patterns, and highlighted the effects of the configuration of EAP and EU on abnormal distribution of the summer precipitation in China in the interannual scale and in the30-60day low frequency oscillation, respectively. Our results are summarized as follows:1. The East Asia Pacific Teleconnection pattern (EAP) and Eurasian Teleconncetion pattern (EU) in the interannual scale are independent of each other with a correlation coefficient of-0.03from1951to2010. There are four configurations between EAP and EU:the significant in-phase configuration (configuration one); the significant out-of-phase configuration (configuration two); EU is dominated (configuration three) and EAP is dominated (configuration four). The different configurations of EAP and EU result in different anomalous circulation and therefore induce the difference of rainfall anomalies in summer, China. When configuration one exists, the area of anomalies of summer rainfall is in the North of China, the Yangtze River becomes the cut-off line of the rain belt. The leaning south wind prevail in most region of China, leading to more rain in the northern region of the Yangtze River than in the southern region as the phases of both EAP and EU are positive; and vice versa. When the configuration between EAP and EU is configuration two, the negative (positive) phase of EAP coexists with the positive (negative) phase of EU, the rainfall will be unusually great (less) in the Yangtze River whereas the rainfall in south China will be less (more) than usual. Furthermore, it should be noted that the anomalous anticyclone (cyclone) circulation and the anomalous cyclone (anticyclone) circulation exist in the southern and northern region of the Yangtze River respectively; resulting in a strong convergence (divergence) in this region. When the EU is dominated, i.e. configuration three exists, the positive (negative) EU led to more (less) rainfall in the upper and middle reaches of the Yangtze River and the southern region of the Yellow River. However, when configuration between EAP and EU is type four, i.e. the negative EAP is dominated, the middle and lower reaches of the Yangtze River becomes the main rainfall anomaly area. The rain belt is northeast-southwest direction. While the positive EAP is dominated, the middle and lower reaches of the Yangtze River have less rainfall.2. The Lake Baikal and Philippines were selected as the reference domains to elucidate the changes of the EAP and EU in the low frequency scale of30to60days. It was found that there are four different phase configurations of these two patterns, and different configurations lead to different characteristics of rainfall.(1) When the peaks of wave of EU and EAP locate at Lake Baikal and Philippines respectively (type one) at the same time, there are "-+-" anomalies which are identified to belong to EU pattern in the low frequency height field in Eurasia middle and high latitude areas. The centers of the anomalies locate at Europe, Lake Baikal and Okhotsk Sea. The East Asia EAP pattern shows "+-" anomalies in the low frequency height field, and the center of its positive anomaly is near Philippines and South China Sea whereas the negative center is over Japan. It is also found that the center of anomaly of EU locates at Okhotsk Sea could couple with that of EAP over the Japan. A northeast-southwest rain belt appears in the low frequency rainfall field under this kind of configuration. As a consequence, the rainfall in the Huanghuai, Yangtse-Huaihe River, Southwest, Northeast areas and Yangtze valley is more than normal whereas the rainfall in other areas of China is less than normal.(2) When the peak locates at Lake Baikal and trough peak at Philippines (type two), a "-+" configuration appears in the Eurasia with its centers at Europe and Lake Baikal. The center of negative anomalies at Okhotsk Sea is relatively weak. Furthermore, configurations of "-+" appear from low to high latitudes in East Asia. When this type of configuration exists, the lower-middle reaches of the Yangtze River have less rainfall than normal although the higher-middle reaches of the Yangtze River and Inner Mongolia show different behaviors.(3) When the trough locates at Lake Baikal and peak at Philippines (type three), a "+-configuration appears in the Eurasia. Furthermore, configurations of "+-" appear from low to high latitudes in East Asia. This kind of configuration of EU and EAP in low frequency scale corresponds to different characteristics of rainfall from that of configuration two. The lower-middle reaches of the Yangtze River have more rainfall than normal although the higher-middle reaches of the Yangtze River and Inner Mongolia have less rainfall.(4) When the troughs of wave of EU and EAP locate at Lake Baikal and Philippines respectively (type four) at the same time, both "+-+" anomalies and "-+" anomalies exist in the low frequency height field. For the "+-+"anomalies, the positive centers locate at Europe, Okhotsk Sea whereas the negative one at Lake Baikal. However, the positive and negative centers locate near Philippines and South China Sea and over Japan. For this configuration, the rainfall in Inner Mongolia and Sichuan basin are more than normal whereas the rainfall in other areas in china is less than normal.