黄河气旋暴雨过程发展演变成因分析

Analysis on the Causes of Development and Evolution of the Yellow River Cyclone Rainstorm Process

2016年7月19-21日华北地区出现了一次影响范围广、累积雨量大、持续时间长、局地雨强大的极端强降水过程,强度仅次于1963年8月8-9日极端降水事件,河北多地及北京的降水总量和持续时间超过2012年"7·21"特大暴雨。本文利用地面自动气象站、气象卫星以及NCEP再分析等资料对导致此次特大暴雨的环流配置尤其是黄河气旋的发生发展等特征进行分析。结果发现,深厚的华北低涡、与低涡相联系的西风槽、副热带高压以及低涡诱发的黄河气旋是此次暴雨的直接影响系统。副高的阻挡使得气旋移动缓慢,且移动过程中两次呈现逆时针旋转路径。地面气旋中心总是沿中低层暖平流和其下游高低层正涡度平流之差较大的区域移动。同时,由于降水产生的凝结潜热释放和上升运动产生的正反馈作用,引导气旋向上升运动强的地方移动。强降水造成的潜热反馈对低层位涡增长起了重要的作用,有利于地面黄河气旋系统生成。同时,高空高位涡沿等熵面下传与低空系统耦合,并与地面气旋上空的暖平流成正反馈作用,进而导致地面黄河气旋迅速发展。卫星水汽图像水汽暗区的干带具有高位涡特征,将其与高层位涡场结合分析,有助于在水汽图像上对高空动力特征的发展演变进行判断,为温带气旋的监测提供参考。

On 19-21 July 2016 North China experienced an extreme rainfall event,which is characterized by wide influence range,large accumulated rainfall,long duration and locally large rainfall intensity. In terms of the rainfall amount,it is the most severe rainfall event since August 1963. The intensity and duration of rainfall in Hebei province and Beijing exceeded that of "7. 21" in 2012. The characteristics of the weather system development,the path of the Yellow River cyclone are analyzed with the data of ground automatic station,satellite and NCEP data. The deep low vortexes over North China,the westerly trough associated with the low vortex,the subtropical high and the Yellow River cyclone induced by the low vortex are the direct influencing systems of the rainstorm. Because of the blocking of the subtropical high,the cyclone moved very slowly. Additionally,the path appears counterclockwise rotation twice during the movement. It is found that the surface cyclone center always moves along the warm advection in the middle and lower layers and the region with large differential vorticity advection in the lower and upper layers. Meanwhile the positive feedback generated by the latent heat release and the vercital movement,guides the cyclone moving to the place where the vertical movement is strong. The latent heat plays an important role in the growth of low level potential vorticity,which is beneficial to the generation of cyclone. At the same time,the high-altitude vortex is coupled with the low-altitude system,and has a positive feedback effect with the warm advection over the surface cyclone,which leads to the rapid development of the surface Yellow River cyclone. The dry zone in the dark region of water vapor in satellite water vapor image has the characteristics of high vortex,which is analyzed by combining it with the high level potential vortex field,which is helpful to judge the development and evolution of high-altitude dynamic characteristics in the water vapor image,and provides reference for the monitoring of extratropical cyclones.