Squall lines are a common form of severe convective weather,characterized by their abrupt onset,short duration,and localized spatial extent.Due to the limitations of conventional observational networks in capturing their detailed structural and dynamic characteristics,high-resolution numerical simulations are essential for in-depth analysis.In mesoscale modeling,microphysics parameterization schemes exert a significant influence on the vertical distribution of temperature and humidity,making them a key factor in accurately reproducing extreme weather events.Therefore,evaluating the performance and mechanisms of different microphysics schemes under specific convective scenarios is critical for improving forecasting and early warning capabilities.Located in the East Asian monsoon region,Jiangsu Province frequently experiences severe convective weather in spring.On April 30,2021,a squall line associated with a severe convective event impacted Nantong,Jiangsu,producing extreme surface winds,including a gust of 47.9 m·s^-1 (Beaufort scale 15) in Tongzhou Bay.This study investigates the event using observational and reanalysis data,along with numerical simulations conducted with the Weather Research and Forecasting (WRF) model employing three microphysics schemes:Lin,Morrison-Gettelman (MG),and WSM6.The analysis focuses on the synoptic environment,structural characteristics,and physical mechanisms associated with the extreme winds and provides a comparative evaluation of the simulation performance.The results indicate the following:1) The squall line developed under the influence of a deep upper-level cold vortex and a strong surface warm-moist low-pressure system,with instability and energy accumulation evident aloft.The system followed a broken-areal development pattern,evolving through initiation,maturity,and dissipation between 1200 and 1300 UTC.Radar observations revealed a bow echo and a V-notch signature.2) The Lin scheme most accurately simulated the life cycle and vertical structure of the squall line,with maximum updrafts of 23.55 m·s^-1 and downdrafts of -13.21 m·s^-1.The MG scheme showed a temporal lag in simulating convective cell evolution,while the WSM6 scheme failed to reproduce a distinct squall-line echo.However,the MG scheme performed best in capturing the intensity and spatial distribution of extreme surface winds,successfully reproducing a maximum gust of 44.47 m·s^-1 consistent with observations.The Lin and WSM6 schemes showed comparable overall performance,with the Lin scheme providing a more realistic thermodynamic structures.3) At the surface,a mesoscale system comprising a rear-wake low,thunderstorm high,and pre-squall mesolow was identified near the squall line.These features,along with cold pool outflows,strong pressure gradients,and cold frontal passage,collectively contributed to the formation of damaging surface gusts.4) Vertically,the convective system was characterized by upper-level divergence,low-level convergence,a mid-level warm layer,and a cold lower layer.Intense updrafts and latent heat release ahead of the squall line,in conjunction with strong vertical wind shear,created a favorable environment for the development of severe surface winds.
This study provides insights into the dynamic and thermodynamic processes driving squall-line-induced damaging winds and assesses the capability of different microphysics schemes in simulating such events.The findings contribute to the advancement of numerical modeling of convective systems and offer reference values for future research.However,as the conclusions are based on a single case study,further validation using multiple events is required.Future work will examine the effects of model horizontal and vertical resolution on the simulation of gust front dynamics and associated thermodynamic processes.