台风“艾云尼”(201804)引发肇庆地区暴雨的成因分析

Analysis of the Causation for a Heavy Rain in Zhaoqing Area Induced by Typhoon Ewiniar (201804)

利用NCEP/NCAR逐6 h 1°×1°全球分析资料、地面自动气象站资料等,从环流形势及主要物理量特征等对2018年首个登陆广东的台风"艾云尼"(1804号)给肇庆地区造成大雨到暴雨、局部大暴雨的天气过程原因进行分析。结果表明:菲律宾东面的热带低压加强,迫使副高东退,"艾云尼"处在弱的引导气流中,移动缓慢,降水时间较长;南海季风输送的暖湿气流、菲律宾以东洋面偏东气流和90°E越赤道北上气流为台风输送高温高湿的水汽,为暴雨产生提供了充沛的水汽;高层辐散、低层辐合,上升运动深厚而强盛,为暴雨的产生提供良好的动力条件;弱冷空气的侵入使斜压性增强,冷暖气流的对峙有利于降水幅度的增加。

Using global 1°×1° reanalysis available every 6 hours from NCEP./NCAR and observations from surface automatic weather stations, this paper studies, from the aspects of circulation patterns and main physical quantities, the causation for a weather process of heavy rain(unusually heavy rain in some locations) in the area of Zhaoqing induced by Typhoon Ewiniar(1804), the first tropical cyclone that ever made landfall in Guangdong in 2018. The result is shown as follows. As a tropical depression intensified to the east of the Philippines, a subtropical high in the western Pacific was forced to retreat eastward and Typhoon Ewiniar was in a weak steering air current so that it moved slowly and brought about rain that maintained over an extended period of time. A warm and humid airflow transported by a monsoon from the South China Sea, an easterly airflow over the ocean to the east of the Philippines and a north-going cross-equatorial airflow at 90°E provided warm and humid water vapor to the typhoon, supplying sufficient amount of water vapor for the generation of heavy rain. The upper level was divergent, the low level was convergent, and ascending motion was deep and intense, dynamically driving the heavy rain. The intrusion of weak cold air increased the baroclinicity of the atmosphere and the confrontation between cold and warm airflows helped increase the rain rate.