Evolution Mechanisms of Surface Winds under the Influence of Cold Pools during a Squall Line Process

As a key boundary-layer feature of squall line systems, the evolution of cold pool intensity is closely related to the generation mechanisms of strong winds. To further investigate the evolutionary mechanisms of strong winds triggered by squall line cold pools, this study conducted a numerical simulation of a squall line event over Jiangsu on July 26, 2022, based on observational data and the WRF (Weather Research and Forecasting) model. Sensitivity experiments were designed by adjusting evaporation process parameters to systematically examine the mechanisms of wind evolution under the influence of cold pools. Results show that, in observations, extensive cold pool boundaries correspond to areas of maximum 10 m wind speed near the surface. Sensitivity experiments revealed that increasing the CONSTB parameter significantly enhances raindrop evaporative cooling, expanding the cold pool’s coverage, causing an average temperature decrease of approximately 4 °C near the cold pool boundary, and an increase of 2.74 m/s in the maximum near-surface wind speed. The temperature gradient at the cold pool boundary widens, leading to an increased pressure gradient and strengthened density current. Consequently, the gust front intensifies, resulting in higher surface wind speeds. Meanwhile, stronger cold pools correspond to more pronounced downdrafts and negative dynamical vertical acceleration in the lower layers. The intense downdrafts facilitate the downward transport of horizontal momentum from upper levels, generating and enhancing strong winds near the surface.