2020年10月海南一次持续强降雨过程分析

Analysis of a Continuous Heavy Rainfall in Hainan in October 2020

利用常规观测资料、多普勒雷达、NCEPFNL1°×1°全球再分析等资料对2020年10月15—19日海南一次持续性强降雨过程进行分析,此次持续强降雨过程是在西太平洋副热带高压较弱、冷空气与南海辐合带相互作用、持续低空急流带来良好动力和水汽条件下形成的。2个强降雨时段(16日20时至17日08时和18日08时至20时)的成因表明:冷涌导致海南岛东北急流长时间维持,东北急流和偏东急流在海南岛中部陆地辐合,有利于对流不稳定能量释放,是第一阶段暴雨形成的主要机制;随着第一次暴雨过程冷空气下沉,释放不稳定能量,假相当位温面逐渐接近垂直,MPV1呈弱负值,低层MPV2出现较大正值,斜压不稳定加强,同时倾斜涡度发展,是南海辐合带略有加强并逐渐北移的主要天气学机制,为海南岛南部陆地带来东南急流,与南压的东北急流辐合,使得不稳定能量重建加强,造成第二次暴雨。

A continuous heavy rainfall process in Hainan from October 15 to 19,2020 was analyzed based on the conventional observation data,Doppler radar and NCEP FNL1°×1°global reanalysis and other data.The continuous heavy rainfall process was caused by the weak subtropical high in the Western Pacific,the interaction between cold air and the South China Sea convergence zone,and the good power and water vapor brought by the continuous low-level jet.Comparison of the causes of the two heavy rainfall periods(20:00 on the 16th to 08:00 on the 17th and 08:00 to 20:00 on the 18th)showed that cold surge led to the long-term maintenance of the northeast jet in Hainan island and the convergence of the northeast jet and the easterly jet in the central part of Hainan island,and was conducive to the release of convective unstable energy,which was the main mechanism of the formation of the first stage rainstorm.With the cold air sinking the unstable energy was released during the first rainstorm,the pseudo equivalent potential temperature surface gradually turned vertical,MPV1 presented a weak negative value,and MPV2 appeared to have a higher positive value in the lower layer,the baroclinic instability strengthened and the inclined vorticity developed.It is the main synoptic mechanism that the convergence zone of the South China Sea slightly strengthened and gradually moved northward,which brought the southeast jet to the southern land of Hainan Island,converging with the southerly northeast jet,and the reconstruction of unstable energy was strengthened,resulting in the second rainstorm.