高层环境场对台风"黑格比"(2020)迅速增强的影响分析OA北大核心CSTPCD

Rapid intensification(RI)remains a challenge in typhoon intensity forecasting.In order to enhance the understanding of the mechanism behind typhoon intensity variation and to improve the accuracy of typhoon intensity forecasts,this study analyzed the characteristics of the upper-tropospheric environmental field during the RI of Typhoon Hagupit(2020).Using the CMA Tropical Cyclone Best Track Dataset and the ERA5 reanalysis data,the present study discussed the possible mechanisms by which the upper-tropospheric environmental field affected typhoon intensity.The results show that:(1)The upper-level weather systems affecting the intensity of Typhoon Hagupit(2020)mainly included the South Asian high,the tropical upper-tropospheric trough,and the mid-latitude trough.(2)The upper-tropospheric environmental field facilitated the intensification of Typhoon Hagupit(2020)through its interaction with the upper-level outflow of the typhoon.On the one hand,favorable upper-tropospheric circulation enhanced the upper-level outflow by directing the eddy flux convergence of relative angular momentum to propagate toward the typhoon center.This process promoted the secondary circulation formed by the outflow and upward motion,leading to a decrease in the central pressure of Typhoon Hagupit(2020)and an increase in its intensity.On the other hand,the enhanced outflow restricted the development of the vertical wind shear and,consequently,weakened the ventilation effect and intensified the typhoon.(3)On the 360-K isentropic surface,the presence of small-scale positive potential vorticity(PV)anomalies atop the typhoon circulation enhanced the typhoon's intensity.At the same time,the"high-PV pool"in the stratosphere was connected with the positive PV anomaly region in the middle troposphere,which could promote the formation of the upper-level warm core and intensify the typhoon.The present study shows that a comprehensive analysis of the upper-tropospheric environmental field can offer insights for typhoon intensity forecasting.