自贡市极端大风过程特征分析

Analysis of Characteristics of Extreme Gale Processes in Zigong

摘要: 本文对自贡地区2018~2023年发生的15次9级以上对流性大风过程进行分析，探究其发生时间特征、环境条件、雷达回波及地面要素特征，结果表明：① 自贡发生9级以上对流性大风分为混合性大风和雷暴大风两类，其中混合性大风高发于春末夏初，雷暴大风高发于盛夏，且以16时和21时为峰值时段；② 物理环境方面，低层和中高层喇叭口状层结是有利层结结构，且Shr500 hPa与对流有效位能(Convective Available Potential Energy, CAPE)呈一定负相关，Pearson相关系数−0.46；③ 雷达回波形态以非线性对流系统为主(29%)，且大多回波强度 ≥ 65 dBZ，短临监测上中层径向辐合(MARC)、低层辐散、低空急流、阵风锋及垂直液态含水量(Vertically Integrated Liquid, VIL)突降为关键监测指标；④ 过程普遍伴随气温骤降、气压涌升及5分钟雨量 ≥ 7 mm的短时强降水。

Abstract: This paper analyzes 15 convective gale processes of magnitude 9 and above that occurred in Zigong from 2018 to 2023, exploring their temporal characteristics, environmental conditions, radar echo features and surface element characteristics. The results show that: ① The convective gales of magnitude 9 and above in Zigong are divided into two categories, namely mixed gales and thunderstorm gales. Mixed gales occur frequently in late spring and early summer, while thunderstorm gales are prevalent in midsummer, with peak hours at 16:00 and 21:00 local time. ② In terms of physical environment, the trumpet-shaped stratification in the lower and middle-upper troposphere is a favorable stratification structure. Moreover, there is a negative correlation between the vertical wind shear at 500 hPa (Shr500 hPa) and Convective Available Potential Energy (CAPE), with a Pearson correlation coefficient of −0.46. ③ The radar echo morphology is dominated by nonlinear convective systems (accounting for 29%), and most of the echo intensities are ≥65 dBZ. For short-range monitoring, mid-altitude radial convergence (MARC), low-level divergence, low-level jet, gust front and sudden drop in Vertically Integrated Liquid (VIL) are the key monitoring indicators. ④ These processes are generally accompanied by abrupt temperature drop, pressure surge and 5-minute rainfall ≥ 7 mm.