“天鸽”台前飑线环境场及雷达回波特征分析

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55dBZ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。

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

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 2000J?kg-1 provide the early thermal conditions for the Pre-TC squall line; (2)the convective cells triggered near the surface convergence line and rapidly develops 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 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 showed 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 55dBZ 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.