夏季西亚副热带西风急流位置对长江源区沱沱河流域径流量的影响

Impact of Position of West Asian Subtropical Westerly Jet in Summer on Runoff over Tuotuo River Basin in Source Region of Yangtze River

基于1979~2016年沱沱河水文站的夏季径流量实测资料、沱沱河气象站的降水和气温资料以及ERA-interim再分析资料,利用相关、回归、EOF等分析方法,研究了夏季西亚副热带西风急流(West Asian Subtropical Westerly Jet,WASWJ)位置对长江源区沱沱河流域径流量的影响特征及其物理机理。结果表明:(1)夏季WASWJ南北位置异常对沱沱河流域径流量有重要影响。当WASWJ偏南(北)时,沱沱河流域径流量偏多(少)。(2) WASWJ位置主要通过调制降水的变化来影响径流量。当WASWJ偏南时,南亚高压明显偏东,沱沱河流域位于对流层中层的负高度异常控制区,全区存在显著的上升运动异常,有利于高原低值系统活动。同时伴随低层明显的西南风异常,加强了来自低纬的水汽输入,导致流域降水增加,径流量偏多。(3)夏季北极涛动(Arctic Oscillation,AO)可通过影响西亚至中亚的对流层中上层温度变化进而对WASWJ南北位置产生明显影响,二者存在显著的负相关关系。研究成果可为气候变化背景下长江源区水资源的合理开发利用提供科学参考依据。

Based on the runoff data from Tuotuo River hydrological station,the precipitation and temperature data from the Tuotuo River meteorological station,the ERA-interim reanalysis data in summer from 1979 to2016,the influence of the position of West Asian Subtropical Westerly Jet( WASWJ) in summer on the runoff over Tuotuo River Basin in the source region of Yangtze River and the corresponding physical mechanism have been investigated,using the methods of correlation,regression,and EOF analysis.Results show that the latitudinal position of the WASWJ has a significant influence on runoff of theTuotuo River Basin in summer.In detail,the southward( northward) WASWJ axis could result in more( less) runoff over there by modulating the change of precipitation.When the jet position is further south,the South Asian high inclines to more eastward position,and the anomalous negative geopotential height and significant ascending movement over the Tuotuo River Basin is conductive to the development of the plateau low-value system,resulting in more precipitation.Meanwhile,the anomalous southwesterly flow is favorable for the water vapor transport from the lower latitudes into the study region,leading to increased precipitation and more runoff formation,and vice versa.Further analysis shows that the Arctic Oscillation( AO) in summer can significantly affect the latitudinal position of WASWJ by affecting the temperature variations in the upper and middle troposphere from West Asia to Central Asia,and there is significant negative correlation between them.The results of this research have important implications for the water resources management in the source region of Yangtze River under global warming.