北京“7·21”特大暴雨过程时空特征解析

Spatial and Temporal Characteristics of a Summer Rainstorm in 2012 in Beijing

利用高密度自动站观测记录和长序列气象站观测资料,对2012年7月21日北京地区特大暴雨过程的时空演化规律进行了分析。结果表明:"7·21"特大暴雨期间,全市累积降雨量大于100mm的站数达到211个,占全部测站数的92%,96个站累积雨量大于200mm,12个站大于300mm;多数地区降雨时长超过16h,密云大成子站降水时间最长,达到20h,强降雨时长在西南房山和门头沟最大;最大小时雨强中心出现在东北和西南区域,东北部最大雨强中心较突出;平均雨强高值阶段出现在21日18:00—21:00,其中19:00雨强最大,达到22mm/h,但最大雨强在70mm/h以上的高强度降雨发生在21日13:00—14:00(门头沟龙泉站)和19:00—22:00,20:00—21:00平谷挂甲峪站高达100.3mm/h;城区及其附近地带20mm以上量级的小时降雨强度较大,同时傍晚阶段平均累积雨量增长速率快,平均小时降水强度偏大;房山站21日雨量位居1961年以来逐年最大日降水量第2位,仅次于1979年7月18日降雨量,而全市15站平均21日雨量打破了1961年以来的最大日降水量记录,比处于第2位的1963年8月9日平均雨量高出43mm。

Based on the high-density precipitation data of automatic weather stations （AWS）, the spatial- temporal characteristics of extremely intensive precipitation on 21and 22 July 2012 over the Beijing area are analyzed. The results show that during the rainstorm, there were 211 stations recorded greater than 100 mm cumulative rainfall except for Yanqing Station, 96 stations recorded greater than 200 mm cumulative precipitation, and 12 stations greater than 300 mm. In most regions, the durations of precipitation were above 16 hours, with the largest in the southwestern Beijing, and the secondary in the northeast of Beijing. The average precipitation intensity exceeded 16 mm/h in Fangshan, and 14 mm/h in northeastern parts of the urban zone, in spite of the fact that precipitation intensities were less than 6 mm/h in the mountains of the north and northwest. The maximum hourly precipitation intensity was found in the northeast of Beijing and the second in the southwest. The larger average precipitation intensities occurred during 18：00-21：00 of 21 July, with the maximum of 22 mm/h recorded at 19：00. Abnormally strong precipitation intensities of more than 70 mm/h appeared during 19：00--22：00 over the whole city and 13：00 14：00 at Longquan Station. The analysis also shows that the 24-h maximum precipitation of Fangshan on 21 July 2012 ranks the second for the time period of 1961 to 2012. The average 24 h maximum precipitation of 15 stations broke the record of Beijing since 1961, much larger than the second （9 August 1963）.