中文摘要：

2013年夏季中国降水总体呈北涝南旱的分布特征,华北地区、东北地区和西北大部降水异常偏多,而淮河流域、云贵高原至江南地区降水异常偏少.2013年夏季降水异常有其特定的环境场和物理机制,首先从东亚大气环流系统相互配置的角度分析了2013年夏季北涝南旱对应环境场的异常,结果表明：2013年夏季东亚夏季风偏强,西太平洋副热带高压（以下简称副高）偏强,位置偏西偏北,加强了水汽向北输送;同时欧亚中高纬地区为冷性低压控制,阻塞高压活动偏少,不利于冷空气南下;冷暖空气在我国北方地区长时间对峙,导致北方降水偏多.其次,探讨了前冬海洋和积雪等外强迫异常对东亚大气环流的可能影响,发现2013年前冬至夏季,赤道太平洋中东部海温偏冷,而北印度洋和西北太平洋海温偏暖,夏季热带沃克（Walker）环流和西太平洋哈得来（Hadley）环流异常,西太平洋南部尤其是菲律宾海附近热带辐合带对流活动偏强,使得副高偏北,东亚夏季风偏强;前冬欧亚积雪异常偏多,有利于夏季贝加尔湖以东盛行深厚的冷性低压,东亚副热带西风急流增强,也有利于副高加强、西伸和北扩.东亚夏季风环流系统既受海温和积雪等外强迫的影响,同时系统之间也存在相互作用,环流系统之间的不同配置是造成区域旱涝异常分布的直接原因.

英文摘要：

On the whole, the distribution of summer precipitation over China in 2013 is lfood in the north and drought in the south. The precipitation anomaly is more than usual in North China, the Northeast and Northwest, while that in the Huaihe River, Yungui Plateau and the south of Yangtze River is less than usual. The summer precipitation anomaly in 2013 has its particular background and physical mechanism. In this paper, we have analyzed the reason of the summer precipitation anomaly in two main aspects: ifrstly, the East Asian atmospheric circulation systems anomaly, which is corresponding with the summer rainfall anomaly, is analyzed. Results show that in 2013 the East Asian summer monsoon (EASM) is stronger, the Western Paciifc Subtropical High (WPSH) is also stronger with the anomalous westward and northward movements of the WPSH, all of which strengthen the water vapor transport northward movements. At the same time, Eurasia mid-high latitude area is controlled by the cold low pressure, blocking high resistance less activity, which is adverse for the cold air moving southward. Cold and warm air masses confront each other in north China for a long time, leading to more precipitation in this area. Secondly, the prophase anomalies, such as previous winter sea surface temperature (SST) anomaly and the snow anomaly, which has a major impact on the atmospheric circulation in East Asia, have been discussed. Results show that from the previous winter to the summer in 2013, the east-central equatorial Paciifc Ocean SST is lower while the north Indian Ocean and the northwest Paciifc SST is higher. The summer tropical Walker circulation and Hadley circulation of West Paciifc ocean is abnormal. In the south of West Paciifc ocean especially near the sea of the Philippines, the convection of the tropical convergence zone is stronger, resulting in the northward of the WPSH and the strengthening of the EASM. The previous winter Eurasian snow anomaly is more than usual, which beneifts for the cold deep low pressure in the south o