基于SPEI的南水北调中线水源区干旱时空特征

利用多种统计方法对南水北调中线水源区降水和气温序列进行趋势诊断,识别了不同气象站点序列的时空变化趋势;以标准化降水蒸散指数(SPEI)为干旱指标,建立考虑降水和气温共同对干旱过程影响的评价模型,研究分析了水源区不同时间尺度和分期(汛期、非汛期和全年期)干旱过程动态变化特征。分析表明:降水量呈现不显著的下降趋势,气温总体呈现显著性上升趋势;短时间尺度SPEI对降水和气温变化更加敏感,随着时间尺度增大,SPEI值变化更加平缓;非汛期和全年期水源区发生严重干旱的概率增大,不同气象站点3个不同时期发生特旱或重旱的年份与历史发生干旱的资料相一致;干旱严重程度从上游到下游逐渐衰减,整个汉江上游和西北部地区干旱发生频次略高于下游和南部地区;对比标准化降水指标(SPI)计算结果,SPEI指数较SPI指数补充考虑了降水和气温对干旱过程的综合影响,可作为SPI指数的一个重要补充分析手段,可应用于描述南水北调中线水源区不同时间尺度的干旱特征。

Spatio-temporal drought characteristics in water source area of Middle Route Project of South-to-North Water Diversion based on SPEI

A variety of statistical techniques were used to detect the trend of precipitation and temperature series from different meteorological sites in the water source area of the Middle Route Project of South-to-North Water Diversion. Based on the standardized precipitation evapotranspiration index (SPEI), a number of drought evaluation models considering the combined impact of precipitation and temperature on the drought process were established, and the dynamic characteristics of the drought process at different time scales and periods (flooding season, dry season and the whole year) were analyzed. The results indicated that the precipitation showed an insignificant decreasing trends, and the temperature exhibited a significant upward trend. The short-term SPEI was more sensitive to precipitation and temperature variations, and the SPEI value fluctuated less as the time scale increased. The probability of severe drought in the water source area showed an increase trend in non-flooding season and the entire year. The occurrence year and frequency of severe drought in three different periods at different meteorological stations were consistent with the historical drought data. The severity of drought gradually declined from upstream to downstream, and the frequency of drought in the upper reaches and northwestern regions of the Hanjiang River was slightly higher than that in the downstream and southern regions. Compared with the standardized precipitation index (SPI) calculation value, the SPEI index supplements the combined effects of precipitation and temperature on the drought process. It can be used as an important supplementary analysis method for the SPI index and applied to describe the drought characteristics of different time scales in the water source area of the Middle Route Project of South-to-North Water Diversion.