基于SPEI指数的长江中下游流域干旱时空特征分析

基于长江中下游流域1961—2015年129个气象站点的逐日气温和降水数据,利用标准化降水蒸散指数(SPEI),对长江中下游流域近55年年尺度及各季节干旱变化趋势、站次比、强度和频率进行了分析,并探讨了干旱和区域气温、降水变化及ENSO的关系。结果表明:(1)在区域尺度,近55年长江中下游流域年尺度、春季和秋季呈干旱化趋势,春季干旱化趋势显著;夏季和冬季呈湿润化趋势。空间变化上,对于年尺度,汉江流域、中游干流区及洞庭湖流域以干旱化趋势为主,鄱阳湖流域、下游干流区和太湖流域以湿润化趋势为主;春季和秋季分别有96.90%和92.25%的站点呈干旱化趋势;夏季和冬季分别有82.95%和72.87%的站点呈湿润化趋势。(2)年尺度、春季和秋季干旱站次比及强度均呈增加趋势,春旱站次比与强度增加趋势显著;夏季和冬季干旱站次比和强度均呈下降趋势。(3)年尺度和春季干旱频率在21世纪初均达到最高,年尺度、春季和夏季干旱频率从20世纪90年代到21世纪初均呈增加趋势。(4)春、秋季干旱化趋势与降水量的减少及气温的上升相关,夏、冬季降水量的增加使得夏、冬季呈湿润化趋势。冬季SOI和次年春季干旱相关性极显著,冬季发生拉尼娜事件时,次年春季更易发生干旱。

Spatial and temporal characteristics analysis of drought based on SPEI in the Middle and Lower Yangtze Basin

Drought is one of the major meteorological disasters in China. In the context of global warming, the losses caused by drought have increased significantly. As an important grain, edible oil, and cotton production area, the Middle and Lower Yangtze Basin is densely populated and economically developed. Although the area is rich in water resources, the temporal distribution of precipitation is uneven and interannual variation is large, which often induces terrible seasonal drought. Based on daily temperature and precipitation data of 129 stations in the Middle and Lower Yangtze Basin, the Standardized Precipitation Evapotranspiration Index (SPEI) was used to analyze the trends, stations proportions, severity, and frequency of annual and seasonal droughts. The relationships between drought and temperature, precipitation, and ENSO (El Niño-Southern Oscillation) were also considered. The regional analysis of SPEI indicated that annual, spring and autumn droughts have become more serious, especially in spring; summer and winter showed a wetter trend. For annual drought, the Han River Basin, Midstream River area, and Dongting Lake Basin were increasingly dry, whereas the Poyang Lake Basin,Downstream River area, and Taihu Lake Basin mainly showed a decreasing trend. For the stations, 96.90% and 92.25% showed a drought trend in the spring and autumn, respectively; 82.95% and 72.87% of stations showed a wetting trend in summer and winter, respectively. The station''s proportions and severity of annual, spring, and autumn droughts all showed an increasing trend. In spring, these trends are significant, while the proportion and severity of summer and winter droughts all showed a decreasing trend. Annual and spring drought frequency peaked at the beginning of the 21st century. Frequency of annual, spring, and summer droughts increased from the 1990s to the beginning of the 21st century. The drought trends of spring and autumn are related to decreases in precipitation and increases in temperature, with the increase in precipitation contributing to the wet trends in summer and winter. There is significant correlation between the spring drought and SOI (Southern Oscillation Index) of last winter. If a La Nina event occurred in winter, the next spring would be increasingly prone to drought.