气候变化背景下长江源区径流变化特征及其成因分析

Changing characteristics and cause analysis of the runoff in the source regions of the Yangtze River under the background of climate change

利用1960-2011年历年逐月长江上游通天河流域直门达水文站观测的流量资料、长江源区气象台站观测资料以及NCEP/NCAR逐月再分析资料,研究分析了长江源区径流变化特征及其气候归因.结果表明:2005年之前,长江源区年及夏、秋、冬季的平均流量呈持续下降趋势,2005年以后,长江源区年及四季的平均流量均呈显著增加趋势.其中,以夏季平均流量的增幅最为明显,年平均流量有4 a左右及12 a左右的变化周期.高原夏季风、长江源区夏季7、8月地面感热、流域降水量、蒸发量、气温及冰川和积雪融水均对长江源区流量变化有明显影响.2005年以后,长江源区年及四季的降水量呈明显的增加趋势,而蒸发量呈明显的减少趋势.同时,温度急剧上升导致的冰川和积雪融水增多,是2005年以来长江源区流量急剧增加的重要原因.

Using the monthly hydrological and meteorological observational data in the source regions of the Yangtze River and the NCEP / NCAR reanalysis monthly data from 1960 to 2011,the variation characteristics of the runoff in the source regions of the Yangtze River and its climate cause have been analyzed by a variety of analytical methods in this paper. Results showthat the annual mean runoff and runoffs in summer,autumn and winter had a persistent declining trend in the source regions of the Yangtze River before 2005,and the annual mean runoff and seasonal mean runoffs have a notable increasing trend in the source regions of the Yangtze River after 2005; especially in summer,the increasing trend is very obvious. In a long-term,the annual mean runoff in the source regions of the Yangtze River varies obviously,with quasi-periods of 4-year and 12-year. The plateau summer monsoon, the surface sensible heat in the source regions from July to August, precipitation,evaporation,temperature and the meltwater from snowand glaciers have evident contribution to the variation of runoff. After 2005,the annual and seasonal precipitations in the regions have increased notably,but the annual and seasonal evaporations in the regions have decreased significantly; the meltwater from snowand glaciers has increased due to temperature increasing notably; all of these have caused runoff sharp increase in the source regions of the Yangtze River since 2005. Under the above background of climate change,the runoff has sharply increased in the source regions of the Yangtze River since 2005.