The Analysis Of Feature Of Anomalies Of Summer Westerly Jet Over East Asian And Relationship Between It And Summer Rainfall In China

Anomalies of the summer westerly jet over East Asian have important impacts on East Asian summer monsoon climate anomalies. Based on the reanalysis data from ERA - 40 datasets supplied by ECMWF with resolution 2. 5°x2. 5° and monthly precipitation of 160 Chinese stations from 1958 to 2000 supplied by National Meteorological Information Center, the climate and space - time characteristic and the interannual variability of summer westerly jet over East Asian are analyzed, then an index—East Asian summer westerly jet index (SWJI)—is defined to represent the location fluctuation of East Asian summer westerly jet (EASWJ). In addition, we study the general circulation feature of SWJI anomaly, relationship between it and Summer Rainfall in China and preceding signal of SWJI anomaly. The results demonstrated that: I. The strongest center of summer zonal wind over East Asian lies in 200hPa, there are two centers in 90°E and 150°E separately. It is shown that the location fluctuations of East Asian summer westerly jet have important impact on Summer Rainfall in China, high SWJI year relates to EASWJ moving north from the average,;vice versa. Variation of SWJI exhibit notable three years and six years low frequency oscillation.II .Anomalies of EASWJ have important effects on Summer Rainfall in China, we find that high SWJI year relates to less rainfall in the mid and lower reaches of Yangtse river and more in south China, the mid-reaches of the Huanghe river;vice versa. III. When the EASWJ moves south from the average, the west Pacific subtropical high andwesterly belt in 500hPa also move south from the average, the cross-equatorial flow in 105cE andEast Asian summer monsoon is weak, there is a negative EAP pattern in 500hPa. The northernflow from higher latitudes and southern flow from lower latitudes converge in the mid and lowerreaches of Yangtse river, resulting in the strengthening and maintenance of Meiyu Front, rainfallin the mid and lower reaches of Yangtse river are more than average.IV.It is shown that the changes of subtropical high, SST of the middle and east equatorial Pacificand subtropical north Pacific have important impact on variability of EASWJ.V. The preceding Nino3 index, zonal wind in 200hPa, Arctic Oscillation Index (AOI) and SLPover East Asian could be used to predict the variability of EASWJ and offer some predictivesignals for the summer precipitation forecasting in China...