中文摘要：

利用1951—2014年南京站逐日降水资料、NCEP/NCAR逐日再分析资料和NOAA逐月海表温度资料,分析了南京夏季降水的逐候演变特征及其异常环流。结果表明：1）南京夏季降水集中在6月第5候至7月第3候,在气候态上降水强度存在峰期位于6月第5候和7月第1候的双峰结构。降水峰期还存在准10 a的年代际变化。2）不同年份降水的候演变特征呈现为峰期在6月第5候、7月第2候的单峰结构以及双峰结构这三种状态之间转换。3）当降水单峰出现在7月第2候（6月第5候）时,同年6月第5候,西太副高偏弱（强）偏东（西）、东亚大槽和贝加尔湖浅槽偏弱（强）、南京附近对流层低层水汽异常辐散（辐合）、中层盛行下沉（上升）运动;同年7月第2候,西太副高偏强（弱）偏西（东）、东亚大槽和贝加尔湖浅槽偏强（弱）、南京附近对流层低层水汽异常辐合（辐散）、中层盛行上升（下沉）运动。4）南京夏季降水的峰期变化与前期冬季（175°E～50°W,10～20°N）区域的SST（Sea Surface Temperature）异常有着较好的相关性。

英文摘要：

Based on daily precipitation data from 1951 to 2014 in Nanjing, NCEP/NCAR daily reanalysis data, and NOAA monthly Extended Reconstructed Sea Surface Temperature data, the pentad evolution characteristics of summer precipitation in Nanjing and its associated anomalous circulation are analyzed using empirical orthogonal function（EOF） decomposition, wavelet analysis, composite analysis, and regression analysis. Results show that summer precipitation in Nanjing is concentrated between the 5th pentad of June and the 3rd pentad of July, and mean precipitation intensity during this period is 8.2 mm ·d-1 .Nevertheless, mean precipitation intensity between the 1st and 3rd pentad of June and between the 4th pentad of July and the 6th pentad of August are only 4 mm ·d-1 and 4.5 mm · d-1,respectively.Precipitation intensity shows a ＂double-peak＂ structure in the climatology, with the peak time occurring in the 5th pentad of June and the 1st pentad of July, with the precipitation intensity in these two pentads both reaching 9.4 mm · d-1.The wavelet analysis results show that the precipitation peak time also has a decadal variation of - 10 years.The pentad evolution characteristics of precipitation shows a conversion between three states-a ＂single-peak＂ structure with the peak time occurring in the 5th pentad of June, a ＂single-peak＂ structure with the peak time occurring in the 2nd pentad of July, and a ＂double-peak＂ structure-in different years.Regression analysis of atmospheric data demonstrates that it is the atmospheric circulation anomalies that lead to the ＂single-peak＂ structure of precipitation.When precipitation＇ s ＂single-peak＂ occurs in the 2nd pentad of July（5th pentad of June）, the western Pacific subtropical high（WPSH） tends to be weak（strong） and eastward（westward） ,the East Asia trough and Baikal shallow trough tend to be weak（strong） ,the vapor in the lower troposphere around Nanjing tends to be anomalously divergent（ convergent）, and the vertical velo