“天鸽”台前飑线环境场及雷达回波特征分析

Characteristics of Circulation Patterns for a Pre-Tropical Cyclone Squall Line of Typhoon Hato and Corresponding Doppler Echoes

利用地面观测资料、ERA5和多普勒天气雷达资料,对2017年8月23日发生在台风“天鸽”前沿的一次飑线过程进行分析。结果表明:(1)近地面显著升温、低层大气暖湿不稳定及CAPE值达2000 J·kg^(-1)以上,为台前飑线形成提供了前期热力条件;(2)对流单体在地面辐合线附近触发并迅速发展成为高度组织化的飑线,其强度、移向与地面风的辐合强弱及位置高度一致;(3)水汽通量中低层辐合、高层辐散的配置保证了短时强降水发生时高效的水汽供应;(4)雷达图上台前飑线发展旺盛阶段中尺度辐合带特征最明显,出现多个55 dBz以上强中心及RIJ特征;(5)当飑线两侧的风向辐合特征减弱时,其带状结构快速断裂且强度减弱,伴随的强对流天气消失。

Based on the ground observation data,ERA5 reanalysis data and Doppler weather radar data,a Pre-Tropical Cyclone(Pre-TC)squall line of typhoon Hato on August 23,2017 was studied.The results show that:(1)the significant near-surface warming,warm and humid instability of the lower atmosphere and the CAPE above 2000 J·kg^(-1) provide the early thermal conditions for the Pre-TC squall line;(2)the convective cells trigger near the surface convergence line and rapidly develop into a highly organized squall line,whose intensity and direction of movement were highly consistent with the convergence strength and location of the surface winds;(3)the configuration of middle and low-level convergence and high-level dispersion of water vapor flux ensures efficient water vapor supply during the occurrence of short-term heavy precipitation;(4)the Doppler radar chart shows that the characteristics of mesoscale convergence zone in the vigorous stage of Pre-TC squall line was the most obvious,with multiple CR centers above 55 dBz and RIJ features;(5)when the convergence characteristics of wind directions on both sides of the squall line was weakened,the band structure broke up rapidly and the intensity diminished,the accompanying strong convective weather disappeared.