偏东风和地形的相互作用对湖南极端强降水的影响分析

Analysis of the influence of interaction between easterly wind and topography on extreme heavy precipitation in Hunan Province

该文利用加密自动站雨量、实况观测资料、FY-2G卫星TBB以及NCEP/FNL每日4次的1°×1°全球再分析资料,对2018年6月19日湖南的中部喇叭口地形处的一次极端强降水天气过程成因进行详细分析。结果表明:①此次极端强降水是在大气环流形势稳定、弱的天气尺度背景下发生的;②不同地形影响下同等强度的对流云团在量级上存在显著差异,异常强的短时强降水出现喇叭口地形附近或迎风坡处。③低层浅薄的偏东风的渗入和中小尺度地形的阻挡和强迫抬升作用,是极端强降水区域出现异常旺盛的上升运动的主要原因;④中层偏东风携带干冷空气侵入近地面发展旺盛的暖倒槽内,是此次强对流天气发生的主要触发机制。地面浅薄的东风气流的长时间维持、南侧偏南气流的加强及地形的阻挡作用有利于地形峡口处的中尺度切变线的长时间维持是强降水持续的主要原因。

In this paper,1°×1° global reanalysis data of encrypted automatic station rainfall,live observation data,FY-2G satellite TBB and NCEP/FNL 4 times a day were used to conduct a detailed analysis on the cause of extreme heavy precipitation weather process in the north of central Hunan province on June 19,2018.The results show that:①the extreme heavy precipitation occurred under the stable atmospheric circulation and weak synoptic scale background;②under the influence of different topography,the convective clouds with the same intensity have significant differences in magnitude,and the short-time heavy precipitation with abnormally strong intensity occurs near the horn mouth topography or on the windward slope.③the infiltration of shallow easterly winds in the lower layer and the blocking and forced uplift of medium and small-scale topography are the main reasons for the extremely vigorous uplift movement in the extreme heavy precipitation region;④the middle easterly wind carrying dry cold air intruded into the warm trough where the development was flourishing near the ground,which was the main trigger mechanism for the occurrence of this severe convection weather. The long-term maintenance of shallow easterly airflow on the ground,the strengthening of southerly airflow on the south side and the blocking effect of the terrain are the main reasons for the continuation of heavy precipitation.