1958—2007年天津降水量和降水日数变化特征

采用1958—2007年天津逐日降水观测数据，探讨降水变化特征。结果表明：近50 a来天津年降水量和年降水日数总体减少，二者每10 a分别减少8.9 mm和4.1 d，其中年降水日数的减少比年降水量的减少显著；四季中，夏冬季降水量明显减少而春秋季呈增加趋势，四季的降水日数均减少；年降水日数在1980年前后有一次明显突变，夏季降水量和春夏秋的降水日数在20世纪70年代和80年代均存在一次明显突变。降水日数和降水量的不同步变化反映发生极端降水事件的概率增加，这对农业生产和生态环境不利。

Characteristics of precipitation and precipitation days from 1958 to 2007 in Tianjin

Based on daily precipitation data from 1958 to 2007 in Tianjin, the characteristics of precipitation were analyzed. The results indicate that annual precipitation and annual precipitation days decrease with 8.9 mm/10 a and 4.1 d/10 a in recent 50 years in Tianjin, respectively. The decreasing trend of annual precipitation days is more significant than that of annual precipitation. Precipitation decreases obviously in summer and winter, while it increases in spring and autumn. Precipitation days are the decreasing trends in four seasons. The obviously abrupt changes of annual precipitation days and summer precipitation occur about 1980 and in 1989 respectively, while abrupt changes of precipitation days in different seasons are in 1970s or 1980s, except in winter. The nonsynchronous variations of precipitation days and precipitation show that extreme precipitation events will increase, which is unfavorable for agricultural production and ecological environment.