1918—2010年天津降水指数变化特征

利用天津1918—2010年逐日降水资料,分析了天津7个降水指数的长期变化趋势。结果发现:天津年降水量和降水日数年际差异较大,没有显著的趋势性变化。从1980年开始天津降水量和日数开始变小(少),方差也变小,四季中秋季降水量呈显著的增加趋势,夏季呈减少趋势,冬、春季变化较小。各极端降水指数中,均表现为线性趋势不明显,年际变化较大,20世纪90年代以来降水强度偏小,但呈缓慢的增加趋势,大雨日数也处于偏少阶段,大雨贡献率偏小,并呈减小趋势。四季中秋季连续5 d最大降水量呈显著的增加趋势,减少了秋季干旱的发生,最长连续无降水日数多发生在冬春季,近年来有增加的趋势。

Variations of Precipitation Indexes in Tianjin During 1918-2010

According to the daily precipitation observation data during 1918-2010 in Tianjin,the long-term tendency of precipitation and extreme precipitation indexes are analyzed.The results show that the annual rainfall and precipitation days have significant interannual fluctuations,but without significant tendencies.The rainfall and precipitation days have displayed a decreasing tendency since 1980,and their variances also become smaller.The rainfall significantly increased in autumn,decreased in summer,and only has small changes in winter and spring.In 1918-2010,all extreme precipitation indexes exhibited no notable linear variation tendency but with large interannual fluctuations.After the1990s,the precipitation intensity was smaller than normal,but showed a slow increasing tendency.The number of heavy rain days was also in a low stage,and its contribution rate to the total precipitation was smaller than normal,and showed a reducing tendency.The maximum rainfall of consecutive 5 days increased significantly in autumn,which reduced the occurrences of autumn drought.The longest consecutive dry days often happened in winter and spring and have increased in recent years.