中文摘要：

利用2011年北京加密自动观测站降水资料、北京站（54511）24 h降水量多年历史资料及NCEP再分析资料,对北京2011年6月1日—8月11日（下称北京汛期）城市暴雨过程、暴雨灾害特点、极端降水特征以及城市化进程对暴雨灾害的影响和成因进行了初步分析。结果表明：（1）2011年6月和7月北京降水量分布不均,呈现从城区向郊县递减的特点,最大降水量中心位于北京城区;汛期共发生8次较强降水天气过程,其中3次造成的气象灾害较大。（2）2011年汛期北京降水量比常年同期偏多54.8 mm,降水量距平自1999年连续12年呈负距平后首次转为正距平。（3）2011年北京极端降水频次、强度分别达到3次和80.7 mm,极端降水量占总降水量的61.4%,较前10年显著提高。（4）2011年北京降水频次变化不大,但暴雨频次显著上升,比前10年同期多2～3次,暴雨量占总降水量比例达60%以上。（5）2011年汛期北京多暴雨是由大气环流和城市化特征共同影响所致。

英文摘要：

Based on the precipitation data from Beijing automatic？weather？station,the 24 h precipitation of historical data from Beijing Station（54511） and NCEP reanalysis data,the urban rainstorm events from 1 June to 11 August of 2011 are tentatively studied including rainstorm disaster features,extreme precipitation characteristics,and influence of urbanization on rainstorm disaster and cause of rainstorm disaster by urbannization.The result shows that the precipitation in June and July 2011 in Beijing tends to be inhomogeneous and decreases from the urban area to the suburbs,and the maximum rainfall center is located in urban area.There are eight heavy precipitation weather processes in Beijing in 2011,resulting in three main weather disasters.The precipitation of Beijing flood season in 2011 is 54.8 mm heavier than usual showing a positive anomaly after the negative anomalies have lasted for 12 years since 1999.The extreme precipitation frequency and intensity in Beijing station in flood season of 2011 is increased to 3 times and 80.7 mm respectively,and the extreme precipitation accounts for 61.4% of the total precipitation,all have significantly increase over the last 10 years.The precipitation frequency in Beijing in 2011 changed a little,but the frequency of heavy rainfall is increased significantly to 2～3 times more than that of the corresponding period over the last 10 years,and the heavy rainfall proportion accounts for more than 60% of the total.The joint function of atmospheric circulation and urbanization factors resulted in more urban rainstorm events in Beijing in 2011.