中文摘要：

利用1961-2004年NCEP／NCAR再分析逐候资料和全国160站月平均降水资料，分析了初夏至盛夏东亚副热带急流北跳和急流中心西移发生早晚对7月东亚大气环流和我国降水的影响。结果表明，急流北跳时间与7月长江中下游地区降水异常正相关，急流中心西移时间则与7月淮河流域降水异常正相关，与华北和河套地区降水异常负相关。急流北跳时间与南亚高压和西太平洋副热带高压南北位置异常及高纬贝加尔湖以东高压脊强度相关；而急流中心西移时间与南亚高压和西太平洋副热带高压的东西伸展及贝加尔湖以西高压脊强度相关，在急流中心西移偏晚年，南亚高压西缩，贝加尔湖西南侧高压脊增强，南下至华北和河套地区冷空气偏强，且西太平洋副热带高压东撤，冷暖空气在淮河流域交汇，使得华北和河套地区降水减少而淮河流域降水偏多；偏早年情况与偏晚年情况相反。

英文摘要：

Using the pentadly averaged NCEP/NCAR reanalysis dataset and the daily precipitation dataset of 714 stations in China from 1961 to 2004, impacts of early or late occurrence of the northward jump of East Asian subtropical westerly jet（EASWJ） and the westward movement of the EASWJ core on the East Asian circulation and the rainfall over eastern China in July are studied. The results are as follows ： （ 1 ） There is closely positive correlation between the date of the northward jump of the jet and July precipitation in the middle-lower Yangtze River basin;the date of the westward movement is positively correlated with July precipitation in the Huaihe River basin, and negatively with July precipitation in North China and the Great Bend of the Huanghe River. （2） The date of the northward jump is related with the meridional locations of the South Asia high ridge and West Pacific subtropical high ridge, and the intensity of the high ridge east of the Baikal Lake; whereas the date of the westward jump is as- sociated with the east-west stretch location of the South Asia high and West Pacific subtropical high, and the intensity of the Baikal Lake high ridge. That is to say, in the later westward movement years, the South Asia high withdraws westwards, and the high ridge southwest of the Baikal Lake strengthens, transporting stronger cold air to North China and the Great Bend of the Huanghe River, meanwhile the West Pacific subtropical high withdraws eastwards, which leads to the confluence of the warm/wet and clod/dry air flows in the Huaihe River basin, bringing more rainfall in the basin and less rainfall in North China and the Great Bend region. The situation is reverse in the earlier years of the westward movement.