首页|2020年7月一场梅雨暴雨的异常空间分布及形成机制

2020年7月一场梅雨暴雨的异常空间分布及形成机制

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  • 国家科技期刊平台
  • NETL
  • NSTL
  • 万方数据
利用GPCP逐日降水资料、NCEP/NCAR和ERA5再分析资料，研究了 2020年7月17-19日长江梅雨大暴雨异常空间分布及成因。结果表明，强降水主雨带在长江下游呈纬向分布，与长江干流位置重合、走向一致、长江中游雨带为西南—东北走向。中高层大气环流出现"两脊一槽"的异常大气环流型，南亚高压主体强盛东伸，副高西北侧水汽通道持续维持，为暴雨的形成和维持提供了有利环流背景。17-18日高空西风急流呈纬向分布、副高控制华南、低空西南急流持续加强并东移;19日高空西风急流转为"V"型分布，江淮气旋形成，长江中下游位于高空急流入口区南侧、副高的西北侧和低空西南急流出口区北侧。"两脊一槽"和"V"型大气环流配置结构使得上层的"抽吸"作用和下层的抬升活动相重叠，伴有江淮气旋的辐合作用，导致强烈的上升运动，易产生大暴雨。过程内高低空急流和副高位置和形态的变化是暴雨空间分布出现变化的主要原因。诊断结果显示，热力因子对抬升活动起主要作用，位涡垂直输送和非绝热加热随气压变化项均有利于位涡增强，假相当位温在500 hPa与850 hPa之差的峰值、强上升运动和位涡高值区与强降水中心重合为本次大暴雨形成提供了有利的热力与动力条件。假相当位温在500 hPa与850 hPa之差的谷值具有较好前期预报指示意义。
Abnormal precipitation pattern of a Meiyu rainstorm event and its dynamical and thermodynamically mechanism in July,2020
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.

Meiyu rainstormupper westerly jetabnormal spatial distributionpotential vorticitycoupling of upper and lower jets

何春杨、杜银、谢志清

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南京信息工程大学大气科学学院,南京 210044

南京信息工程大学气象灾害教育部重点实验室/气象灾害预报预警与评估协同创新中心,南京 210044

江苏省气候中心,南京 210041

大暴雨 高空西风急流 异常空间分布 位涡 高低空急流耦合

国家自然科学基金资助项目国家自然科学基金资助项目国家自然科学基金资助项目国家重点研发计划资助项目大学生创新创业训练计划

4207502742075118419309692020YFA0608901XJDC202210300005

2024

10.12306/2022jms.0098

气象科学
江苏省气象学会

气象科学

CSTPCD
影响因子：0.925
ISSN：1009-0827
年,卷(期)：2024.44(3)
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