松花江流域盛夏降水分布型的环流差异及影响机制

Circulation Differences and Influence Mechanisms of Distribution Modes of Midsummer Precipitation in the Songhua River Basin

利用1961-2017年松花江流域盛夏降水资料、NCEP再分析资料和NOAA/CPC遥相关型指数等资料,采用多种统计方法,研究了松花江流域盛夏降水的主要时空分布及环流特征、影响机制。结果表明:松花江流域盛夏降水有全流域一致型、西北-东南反位相型和东北-西南反位相型三个主要模态。第一模态受PEA(Polar/Eurasiol Pattern)遥相关指数影响,PEA遥相关型负位相年,极涡偏弱,流域上空呈东高西低分布特征,西南低空急流加强的水汽输送至松花江流域;PEA和EAP(East Asia-Pacifio Pattern)相互配合共同作用对产生第二模态降水分布型起主要作用,贝加尔湖呈现显著负距平,冷空气沿超极地路径南下,暖湿气流沿异常偏北的副高边缘向流域输送,并在东南部与冷空气交绥;第三模态降水正异常时,贝加尔湖至鄂霍次克海地区呈显著负距平,东亚夏季风偏强导致副高北抬,呈南高北低分布。

Based on midsummer rainfall data in the Songhua River Basin,NCEP reanalysis dataset and NOAA/CPC teleconnection indice from 1961 to 2017,the main spatial and temporal distribution,circulation characteristics and influence mechanisms of the midsummer precipitation in the Songhua River Basin are studied by varied statistical approaches.Results indicate that there mainly exist three dominant rainfall modes in the Songhua River Basin:The whole basin consistent rainfall mode,the northwest-southeast anti-phase rainfall mode and the northeast-southwest anti-phase rainfall mode.The first mode is affected by the PEA teleconnection type.In the years when the PEA teleconnection index is negative,the polar vortex being weak,circulation of the area is characterized by high-east and low-west distribution,and the vapor enhanced by the southwest low-level jet stream is transported to the Songhua River Basin.The interaction of PEA and EAP plays a major role in the generation of the second mode rainfall distribution.The Baikal Lake exhibits a significant negative anomaly,the cold air flows south along the ultrapolar path,and the warm and humid airflow is transported along the anomalous northerly subtropical high edge to the basin and intersects with the cold air in the southeast.When the third rainfall mode is positively abnormal,there is a significant negative anomaly from the Baikal to the Okhotsk Sea area,the strong East Asian summer monsoon causes the subtropical high to move northward,the circulation situation poses high-south and low-north distribution.