中文摘要：

合成分析了La Nina年东亚夏季风和东亚夏季降水的季节内变化。结果表明。La Nina年夏季暖池对流偏强，西太平洋出现异常气旋，西太平洋副高偏向东北。这种异常型随季节进程有明显变化，7月异常达到最大。La Nina年东亚降水呈纬向型分布，中国东部降水偏少，西太平洋海面降水偏多。与此相比，EI Nina年降水呈经向型分布，热带降水偏少，副热带和中纬度降水偏多。因此，不能简单将La Nina的影响认为是EI Nina的反对称。

英文摘要：

Based on the composite result of six major the intraseasonal variation of the East Asian La Nina events during 1979-2012, the authors reveal summer monsoon （EASM） and summer rainfall in East Asia in La Nino years. Due to a higher SST over the western Pacific warm pool in the proceeding winter and spring, warm pool convection in summer is enhanced, leading to a cyclonic anomaly in the subtropical western Pacific. As a result, the western Pacific subtropical high is located more northeastward, and the seasonal march in East Asia is thus accelerated.This anomalous pattern tends to change with the seasonal march, with a maximum anomaly in July. Besides, there is less Mei-yu rainfall in the Yangtze River basin, with an earlier start and termination. The rainfall distribution in East Asia during La Nino years is characterized bya zonal pattern of less rainfall in eastern China and more rainfall over the oceanic region of the western Pacific. By comparison, a meridional pattern is found during El Nino years, with less rainfall in the tropics and more rainfall in the subtropics and midlatitudes. Therefore, the influence of La Nino on the EASM cannot be simply attributed to an antisymmetric influence of El Nino.