为了揭示20世纪90年代上海地区降水资源的变化特点,根据1991—2003年上海地区11个站降水资料,在与前30年(1961—1990年)平均比较的基础上,统计分析1991年以来降水量、降水日数、相对湿度、蒸发量、降雪日的变化情况,结果表明:20世纪90年代以后,上海地区年平均降水量增加11%,汛期平均雨量增加18%,年平均降水日数却略有减少,这样使年平均降水强度增强了12%,季节分配格局改变,区域分布格局未变;年平均相对湿度和年平均蒸发量略减小,年平均降雪日数减少5d。

Precipitation has become more concentrated in Shanghai since the 1990s.For revealing the changing characteristics of precipitation resource in Shanghai since the 1990s and working out more scientifically measures of controlling flood and combating drought in Shanghai,the statistical characteristic changes of precipitation,the number of precipitation days,relative humidity,evaporation,and the number of snowfall days since the 1990s were studied based on analysis of precipitation data of 11 meteorological stations during the last 13 year(1991-2003) in Shanghai and compared with the mean values of the first 30 years(1961-1990).The results showed the annual average precipitation increased 11%,the average precipitation of flood season increased 18%,the annual average precipitation days decreased 2d,the annual average precipitation intensity increased 12%,the seasonal distribution pattern of precipitation changed,and the regional distribution pattern of precipitation remained unchanged;the annual average relative humidity and evaporation decreased slightly,the annual average snowfall days decreased 5d in Shanghai since the 1990s.The summer precipitation increased evidently and the autumn precipitation decreased.Such a variational difference resulted in changes in precipitation distribution pattern of the four seasons,and much more prominence in drought and waterlogging phenomena in Shanghai.However,the geographic distribution pattern of precipitation of various seasons did not change,only the regional difference became greater. Since waterlogging rather than drought has always been a headache in Shanghai,the flood control departments of the city should attach importance to dealing with serious disasters induced by concentrated summer precipitation.