Analysis on Formation Reason of an Extreme Gale in Sichuan Basin
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Abstract:
Convective extreme gale is one of the main types of severe convective weather that causes meteorological disasters. It has the characteristics of strong locality, short life history, and difficulty in forecasting. In recent years, extreme gale events occur frequently in China, causing serious economic losses to the society and public. However, the characteristics, impact systems, and causes of extreme gale vary in different regions. At present, there are many studies on the background of extreme gales in the Sichuan Basin, but research on convective potential and Doppler radar characteristics is still relatively limited. Therefore, it is necessary to conduct detailed research on typical cases of extreme gales that occur. On 11 April 2022, a rare extreme gale process occurred in Sichuan Basin with maximum wind speed reaching 37.4 m/s. During this period, there were also hail and short-time heavy rain. To explore the causes of this extreme gale process, this paper conducts research and analysis on circulation situation, convective environmental conditions, and meso-small scale system characteristics by using surface hourly meteorological observation data, upper-air observation data, Doppler radar products, and black body temperature data from the FY-2H satellite, providing reference for future forecasting of extreme gale weather in the Sichuan Basin. The conclusions are as follows: (1) This extreme gale process was triggered by the dry and cold air entering the basin, and the forced uplift of the ground convergence line strengthened the storm weather; the unstable stratification featuring “upper dry and lower humid”, a large temperature lapse rate, vertical wind shear with moderate intensity, and high CAPE value, all provided favourable convective environmental conditions for this extreme gale process, (2) The severe weather of this process mostly occurred during the period of severe development and consolidation of the Mesoscale Convective System, and was located in the high-value area of TBB gradient in front of the convective cloud clusters and near the low-value centre of TBB, (3) The main factors causing extreme strong wind on the ground included the cold pool effect when the squall line passed through, and the strong pressure gradient and density current, (4) The front inflow and the rear inflow of the storm together with the strong mid-altitude radial convergence were favourable conditions for the emergence of extreme strong wind; the sharp decrease of the reflectivity factor core and the maximum vertically integrated liquid water implied the humid critical strike flow caused by a sharp drop in temperature in the system, which increased the intensity of strong wind.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.