台风"烟花"影响下一次午后强对流雨带的成因分析OA

Under the influence of the weakened low-pressure circulation of Typhoon"IN-FA"after landfall,a narrow convective rainband developed in Tianchang area along the border of Jiangsu and Anhui provinces in the afternoon of July 28,2021.The rainband moved in the direction of east by north,causing severe wind and rainfall in Tianchang and surrounding areas.Based on multi-source observations and high-resolution simulations using the Weather Research and Forecasting(WRF)model,this study investigates the formation mechanisms of the convective rainband from both dynamic and thermodynamic perspectives.Results indicate that the typhoon's low-pressure circulation provided a warm and humid environment favorable for convection.Afternoon solar radiation increased surface temperatures,enabling the near-saturated air to hold more moisture.Combined with water vapor transport by southerly flow on the eastern flank of the low-pressure circulation,low-level humidity and convective available potential energy(CAPE)increased,leading to the development of convective instability.The interaction between the low-pressure circulation and the westerly trough introduced dry and cold air in the mid-troposphere,further enhancing instability through an upper-dry and lower-wet stratification.Perturbation convergence of low-level winds triggered local convection,while convergence in the middle and lower levels and upward vorticity transport contributed to local vorticity growth.After initiation,convective cells organized into a north-south-oriented severe convective rainband that propagated east-northeastward under the influence of the low-pressure circulation.Sensitivity experiments highlight the critical role of afternoon radiative heating in increasing low-level humidity and CAPE,thereby facilitating the development of the severe convective rainband.