滦河流域多时间尺度干旱时空特征分析

Temporal and Spatial Characteristics of Drought on Multiple Time Scales in the Luanhe River Basin

以滦河潘家口水库控制流域26个雨量站1959-2011年逐月降水数据为基础,应用经验Copula函数建立了联合降水亏缺指数,与标准化降水指数的干旱评价结果进行了对比,并依据联合降水亏缺指数分析了1959-2011年间流域干旱时空变化特征。结果表明:(1)联合降水亏缺指数综合了多时间尺度水分亏缺信息,充分考虑干旱的累积效应,避免了采用不同时间尺度标准化降水指数表征干旱时结论不一致的情况,可以实现更全面客观的干旱监测及评估。(2)1959-2011年,滦河潘家口水库控制流域干旱发生频率总体上呈现夏秋多冬春少、东南高西北低的规律;干旱事件随时间持续增多,特别是2010-2011年极端干旱频繁发生;相比西北部,流域东南部的干旱事件历时更长、强度更大;在汛期(尤其是8-9月)全流域存在较一致的干旱加剧趋势,东南部趋势显著。联合降水亏缺指数能够有效地反映干旱时空特征及演变规律,为区域干旱研究提供了新的技术途径。

In order to provide more objective description of the overall drought status,this paper employed a joint precipitation deficit index by empirical Copula function to evaluate drought condition.The Panjiakou Reservoir catchment of Luanhe River basin was chose as the study area.The accumulated precipitation from 1-to 12-month were selected from the monthly precipitation data from 26 rain gauges during the period of 1959-2011.Based on the values of standardized precipitation index and joint precipitation deficit index,we assessed and analyzed the drought conditions in the study area.It was demonstrated that the joint precipitation deficit index integrates the information of water deficit status at various time scales and takes a full consideration of the cumulative effects of drought.It also can avoid the inconsistent conclusions resulting from using standardized precipitation index with different time scales.In addition,the drought characteristics of the study area were analyzed according to the series of joint precipitation deficit index.The results indicated that the occurrence frequency of the drought generally increases from northwest to southeast,with higher frequency in summer and autumn.Compared with the northwestern part of the area,the drought events in the southeast are characterized with longer duration and more serious severity.Furthermore,a general tendency of drying was found in the flood season across the area,while significant aggravating trends in drought were detected in the southeastern part.The joint precipitation deficit index is capable of reflecting the drought spatial and temporal characteristics and evolution laws,thereby taking as a new technical way of studying regional drought.