气象科学2024，Vol.44Issue(3)：512-526,15.DOI:10.12306/2022jms.0098
2020年7月一场梅雨暴雨的异常空间分布及形成机制
Abnormal precipitation pattern of a Meiyu rainstorm event and its dynamical and thermodynamically mechanism in July,2020
摘要
Abstract
Based on the GPCP daily precipitation data,the NCEP/NCAR and ERA5 reanalysis data,the abnormal spatial characteristics and the physical mechanism of a Meiyu rainstorm event in the middle and lower reaches of the Yangtze River on July 17-19,2020 were analyzed.Results reveal that this heavy rainfall event forms a zonal main rain belt in the lower reaches of the Yangtze River,with an orientation similar to the main stream of the Yangtze River.The main rain belt shows a southwest-northeast orientation in the middle reaches of the Yangtze River.Correspondingly,the atmospheric circulation in middle and upper troposphere shows an abnormal spatial structure that is a V-shape pattern with two ridges and one trough over the Eurasian region.The atmospheric circulation pattern consists of a strong eastward-extending South Asian high at the 100 hPa level,a quasi-barotropic structure in the middle and upper troposphere at the middle and high latitudes,and a baroclinic structure in the middle troposphere.The strong vapor transport stably maintains along the northwest frank of the subtropical high.Particularly,the upper westerly jet shows a zonally pattern on July 17-18,2020,with a subtropical high covering over the South China and a strengthened low-level southwest jet;the upper westerly jet transformed into a V-shaped structure,and the Jiang-huai cyclone formed on the July 19.The middle and lower reaches of the Yangtze River located on the south side of the upper westerly jet entrance and the northwest side of the subtropical high and the low-level jet.The"pumping"effects occurred in the upper troposphere owing to the atmospheric circulation structure of the V-shaped structure and overlapped with the uplifting activity in the lower troposphere,which is conducive to generating strong ascending motions and torrential rainfall.The position and shape of upper and lower jets and the subtropical high play an important role in determining the location,spatial distribution and intensity of heavy precipitation.The strong differences in pseudo-equivalent potential temperature between 500 and 850 hPa levels,the strong upward motions and the high potential vorticity values provided favorable thermodynamic and dynamic conditions for this Meiyu rainstorm event,in which thermal factors dominantly controlled the ascending motion and the vertical transport of the potential vorticity and the non-adiabatic heating term with the pressure are conducive to the enhancement of the potential vorticity according to the ω and potential vorticity tendency equations.The strong differences in pseudo-equivalent potential temperature between 500 and 850 hPa levels is a good significance indication for early prediction.关键词
大暴雨/高空西风急流/异常空间分布/位涡/高低空急流耦合Key words
Meiyu rainstorm/upper westerly jet/abnormal spatial distribution/potential vorticity/coupling of upper and lower jets分类
天文与地球科学引用本文复制引用
何春杨,杜银,谢志清..2020年7月一场梅雨暴雨的异常空间分布及形成机制[J].气象科学,2024,44(3):512-526,15.基金项目
国家自然科学基金资助项目(42075027 （）
42075118 （）
41930969) （）
国家重点研发计划资助项目(2020YFA0608901) （2020YFA0608901）
大学生创新创业训练计划(XJDC202210300005) （XJDC202210300005）
