北京地区夏季极端降水变化特征及城市化的影响

摘要

Based on the summer precipitation data of 20 stations in Beijing and its urban development statis-tical data during 1971-2010,and defining the 95th percentile as the threshold of extreme precipitation for each station,the characteristics of the spatio-temporal distribution and the linear trend of extreme precipi-tation events with different durations and city effect of local precipitation are analyzed.The results indicate that the extreme precipitation event frequency shows a gradual decreasing trend from west to east,which is remarkably different from the precipitation distribution.There exist distinctive spatial differences in the distributive features and changes of the threshold values,frequencies,and rainfall of extreme precipitation events.The averaged intensity and frequency of extreme precipitation in Beijing Area show a descending trend in the past 40 years and have significant difference at interannual and interdecadal changes.The im-pact of urbanization on the intensity and frequency of extreme precipitation has become more and more ap-parent.Urbanization can not only enhance rain island effect but also make an influence on precipitation in downwind areas;moreover,urbanization can also increase the intensity and frequency of local extreme pre-cipitation.%提应用北京地区20站1971-2010年降水记录及城市发展数据，采用百分位方法定义极端降水事件的阈值，分析了北京地区夏季极端降水事件的时空变化特征及城市化的影响。结果表明：（1）北京夏季极端降水阈值及频数存在较强局地性特征，基本沿地形高度分布，极端降水频数多发区与高阈值区不完全对应；（2）近40年极端降水频率及强度均呈现下降趋势，年际及年代际差异显著；（3）城市化发展不同阶段极端降水强度及频数均有不同的分布形态，城市化对城市不同区域极端降水影响不一样，城市化导致城市下风向近郊区极端降水强度、次数均表现为增多趋势；（4）城市对极端降水的影响还与天气过程强度有关，强天气背景下城市对极端降水频数的影响程度高于对降水强度的影响。