海河流域近50年降水量时空变化特征分析

依据海河流域1960—2010年逐日降水资料,采用泰森多边形方法将各站点的降水量展布到全流域,并采用M-K法计算Kendall倾斜度,分析降水的时空变化特征。结果表明:时间上,海河流域总体降水呈减少趋势,春季降水虽然呈增加趋势,但仍是少雨季节,夏季降水变化趋势缓慢,少雨现象出现的频率相对较小,秋季降水逐渐减少,少雨现象出现的频率与春季相似,冬季出现极端降水情况,降水呈增加趋势,降水等级集中在极度少雨,另外,存在春夏连续少雨、秋冬连续少雨,甚至四季连续少雨的情况;空间上,整个流域年降水量由南向北逐渐减少,春季五台山、天津变化显著,夏季全流域降水量呈增加趋势,且渤海西南地区增加显著,秋季全流域中东部分降水趋势下降显著,冬季全流域降水上升、下降趋势变化均较缓慢。

Characteristics of temporal and spatial variation of precipitation in Haihe River Basin during recent 50 years

According to the precipitation data of Haihe River Basin during 1960—2010,the Tyson polygon is applied in the study to distribute the precipitation in every station of the whole basin.The Kendall tilt is calculated with the M-K and the characteristics of spatial and temporal variation of precipitation in the area is analysed.The results show that the overall precipitation is decreasing in time.Although the precipitation is increasing in spring,there is still very little rain.The variation of precipitation in summer is slow and the frequency of drought is relatively small.The precipitation in autumn is gradually decreasing and the drought level is similar to that of spring.There are no significant changes of precipitation and the level of precipitation is extremely little in winter.Besides,the continuous rainless phenomenon occurs in the period from spring to summer,or from autumn to winter,or even consecutively for four seasons.In space,the annual precipitation of the whole basin is gradually decreasing from south to North.Significant changes have taken place in Wutai Mountains and Tianjin in spring.The precipitation in the basin is increasing in summer,especially in the southwest part of Bohai area.It is decreasing significantly in the midle and east part of the whole basin.The precipitation is increasing in winter and the downtrend is slow in the whole basin.