洞庭湖流域雨季极端降水事件的环流演变特征分析
龙浠玉1, 张新主1, 章新平1, 李巧媛2

(1.湖南师范大学 资源与环境科学学院, 长沙 410081; 2.湖南省气象台, 长沙 410118)

极端降水; som-k聚类; 环流演变

Analysis on the Characteristices of Circulation Evolution of Extreme Rainfall Events During the Rainy Season in Donting Lake Basin
LONG Xiyu1, ZHANG Xinzhu1, ZHANG Xinping1, LI Qiaoyuan2

(1.College of Resources and Environmental Sciences, Hunan Normal University, Changsha 410081, China; 2.Hunan Provincial Meteorological Station, Changsha 410118, China)

extreme rainfall; som-k clustering; circulation evolution

备注

基于洞庭湖流域85个气象站点1961—2016年日降水数据和美国NCEP再分析数据,分析了洞庭湖流域1961—2016年雨季(5—9月)极端降水事件环流演变特征,考虑到极端降水的空间差异性,先采用som-k方法对极端降水数据聚类,再分析不同类型极端降水事件的环流演变规律。结果 表明:低对流层气旋性涡旋的发展、500 hPa低压槽的加强、洞庭湖流域东南侧辐合带增强是该区域极端降水发生的重要原因,辐合上升运动区明显增强北移。各类别极端降水异常水汽输送通道并不一致,但异常水汽都主要来源于孟加拉湾、南海、西太平洋,受西太平洋副热带高压西侧的异常水汽流影响。西太平洋副热带高压的季节变化配合大气环流形势差异,导致动力上升条件不同,造成了洞庭湖流域极端降水事件的时空差异:北部型分布在27°—30°N,集中在6月、7月; 中部型分布在26°—27°N,集中在5月、6月; 南部型分布在25°—26°N,集中在5月、6月。

Based on the daily precipitation data of 56 years(1961—2016)in 85 meteorological stations and daily reanalysis dataset from NCEP, a detailed analysis is performed to understand the circulation evolution characteristices of extreme rainfall events(ERT)during the rainy reason(May to September)in Dongting Lake Basin. Som-k(Self Organizing Map and kmeans)is used to cluster the ERT. Based on the foregoing work, the evolution characteristices of different regions of ERT are explored. The results show that there are many reasons for the extreme rainfall, such as the development of low tropospheric cyclonic vorticity, the enhancement of trough at 500 hPa and the enhancement of convergence zone in the southeast side of Dongting Lake Basin, and the central area of upward flow is enhanced and moves northward. Although the anomalous moisture transport channels of ERT in various regions are not consistent, the source of anomalous moisture is basically the same. The excessive anomalous moisture transported from the Bay of Bengal, the South China Sea and the Western Pacific plays an important role in producing environmental conditions favorable for ERT. The seasonal variation of the Western Pacific subtropical high pressure and the difference of synoptic condition cause the spatial variability of the main extreme rainfall rain-band together in Dongting Lake Basin: the ERT of northern region cover about 27°—30°N, which concentrate in June and July, ERT of the central region cover about 26°—27°N, which concentrate in May and June; and ERT of the south region cover about 25°—26°N, which concentrate in May and June. The extreme precipitation rain-band and the location of the anomalous moisture convergence center zone of each category region are coincident.