2017年华西秋雨的环流特征及成因

Anomalous Circulation Characteristics of Autumn Rain and Its Cause over West China in 2017

利用NCEP/NCAR再分析逐日资料、国家气候中心降水逐日资料等,分析了2017年华西秋雨的大尺度环流和物理量场配置。结果表明:2017年秋季,华西地区雨量大、雨日多,多雨区位置偏东,强降水过程频繁。北欧阻塞高压强大且位置偏西,副高强度偏强且位置偏西、偏北,贝加尔湖至乌拉尔山南部为一宽广槽区,冷空气主要从西路影响华西地区,同时还有北方弱冷空气,经渤海从对流层低层回流到华西地区;高空急流轴在30°N—38°N稳定维持,华西地区位于急流入口区南侧的高空辐散区,低层对应辐合区;在110°E附近存在一强能量锋区,弱冷气流从对流层低层侵入,加剧了能量锋区强度,易于触发不稳定能量爆发,导致华西区域性大暴雨过程。

Based on NCEP/NCAR reanalysis data and National Climate Center precipitation data,the large-scale atmospheric circulation characteristics and physical variables field configuration of autumn rain over West China in 2017 were analyzed.The results show that the amount and days of precipitation over West China in autumn of 2017 were bigger and more than those of normal year,the location of rainfall region was to the east and south,and the strong rainfall events were frequent.Compared with the normal state,the blocking high over Northern Europe was strong and its position leaned toward west,the subtropical high was strong and its position moved westward and northward in autumn of 2017,and the wide trough dominated over Baikal Lake to the south of the Urals Mountains.West China was mainly affected by cold air from the west path in autumn of 2017.At the same time,the weak cold air from the North flowed back to West China from the lower troposphere.The upper level westerly jet axis maintained over 30°N to 38°N,and West China located in the upper-level divergence area in southern side of the jet entrance,and corresponding convergence in low level of troposphere.A strong energy front zone appeared nearby 110°E,and the easterly weak cold air from the North invaded into the front zone from the lower troposphere,which strengthened the energy front zone,triggered unstable energy,and consequently caused regional heavy rainfall in West China.