大渡河流域降水时空变化及环流特征分析

Temporal and Spatial Variation of Precipitation and Circulation Characteristics in Dadu River Basin

为全面了解大渡河流域降水变化规律,将大渡河流域分成4个区域,利用降水融合数据、地面观测数据和NCEP/NCAR再分析资料,对大渡河流域降水时空分布特征,降水变化主模态及其与大气环流的关系进行研究。结果表明,大渡河流域降水时空分布差异较大,最大中心位于二区,其中一、二、三区的降水呈现减少趋势,主要发生在夏秋季,而四区呈现增加趋势,主要发生在春季和夏季。大渡河流域降水变化前三主模态为全区一致型,西北东南反向型和"+-+"三极子型。合成分析表明大渡河流域夏季降水偏多时,西太平洋副热带高压位置偏西,南亚高压偏东,高原夏季风偏强,大渡河流域上空对流层中低层风场为南风异常。

In order to comprehensively understand the law of precipitation change in Dadu River Basin,the Dadu River basin was divided into four regions.The spatial and temporal distribution characteristics of precipitation,the main modes of precipitation change in Dadu River Basin and their relationship with atmospheric circulation were analyzed by using precipitation fusion data,ground surface observations and NCEP/NCAR reanalysis data.The results show that the Dadu River Basin has a great difference in the spatial and temporal distribution of precipitation,and the largest center is located in the second region,among which the precipitation in the first,second and third regions presents a decreasing trend,whichmainly happens in summer and autumn.While the precipitation in the fourth region presents an increasing trend,which mainly happens in spring and summer.The first three main modes of precipitation change in Dadu River Basin are region-wide consistent pattern,northwest-southeast reverse pattern and"+-+"tripole pattern.The synthetic analysis shows that the Dadu River Basin has more summer precipitation,when the position of the western Pacific subtropical high is to the west and the South Asia high is to the east,the plateau summer monsoon is stronger.In that case,the wind field in the middle and lower troposphere over the Dadu River Basin is anomaly southerly wind.