青藏高原江河源区干湿变化特征及影响因素分析

Characteristics of Dry and Wet Variation and Its Influences in the Source Region of the Yangtze and Yellow River in the Qinghai-Tibet Plateau

基于青藏高原江河源区内6个气象站点1961~2014年逐日气象资料,采用Penman-Monteith模型计算了标准降水蒸散指数SSPEI,研究了不同时间尺度下的干湿演变特征及其干旱频率空间分布特征,并分析了影响因素。结果表明,年际变化上,长江源区1969年后SSPEI整体呈显著上升趋势,并在2008年发生突变,黄河源区不同年代变化趋势不同,但整体呈不显著的下降趋势,无突变发生;季节变化上,对研究区影响较大的中旱和重旱集中在5~6月,湿润化趋势和干旱化趋势主要出现在长江源区夏季和黄河源区秋季,春季均无明显趋势;区内夏季SSPEI的Hurst指数几乎都大于0.5,有较好的持续性,春秋两季恰好相反,更多体现了反持续性。趋势分析和偏相关性分析发现,整体上长江源降水增多和风速减小是其湿润化的主要原因,黄河源平均气温上升和相对湿度下降是其干旱化的主要原因。

Based on the daily meteorological data of 6meteorological stations in the source region of the Yangtze and Yellow River in the Qinghai-Tibet Plateau from 1961 to 2014,standardized precipitation evapotranspiration index（SSPEI）was calculated by using Penman-Monteith model.Subsequently,it was analyzed the spatial distribution characteristics of wetting and drying climatic change,drought frequency and its influences in various time scales.The results show that the annual SSPEI,which changed abruptly in 2008,had a significant rising tendency in the source region of Yangtze River after1969.Annual trend of SSPEI without abrupt change was different in different eras but non-significantly decreased as a whole in the source region of the Yellow River.Moderate drought and severe drought which influenced the study area seriously,mainly concentrated in May and June.Wetting in the source region of Yangtze River and drying in the source region of Yellow River mostly occurred in summer and autumn.Almost all Hurst indexes of summer SSPEIin the regions were greater than 0.5,which means good persistence,while contrary to spring and autumn in which SSPEIexpressed anticontinuity.By trend analysis and partial correlation analysis in these regions,wetting was mainly due to more precipitation and less wind,and drying was mainly due to temperature rising and humidity decreasing.