东移型西南涡对长三角地区区域性暴雨的影响分析

Analysis of impact of eastward-moving southwest vortices on regional heavy rainfall in Yangtze River Delta

摘要

【目的】东移型西南涡是影响我国长三角旱涝变化的重要天气系统,但该系统对长三角地区的具体影响尚不完全明确。为研究西南涡东移对长三角地区区域性暴雨的具体影响特征,【方法】基于《西南低涡年鉴》、CN05.1格点降水数据和ERA5再分析资料,对西南涡移动特征和受西南涡东移影响而产生的长三角区域性暴雨特征进行了统计分析和个例对比。【结果】结果显示:2012—2019年共形成716例西南涡,其中西南涡移出源地的路径特征主要表现为向东移动,东移型西南涡约占生成总数的30%,其影响的降水贡献占比约为长三角地区总降水量的10%以上。【结论】结果表明:当东亚大槽和西北太平洋副热带高压的强度偏强时,有利于西南涡的东移发展;东移型西南涡对长三角降水的影响存在明显的空间不均匀性,最大贡献区域主要位于长三角西部;降水大值区与西南涡移动路径、低涡南侧西南暖湿气流的强度、高低空强辐合辐散区位置基本一致。东移型西南涡影响长三角暴雨的具体特征,大型环流形势及中小尺度动力配置,显示了其对长三角暴雨的独特影响,为实际预报东移型西南涡可能导致长三角暴雨天气提供一定的理论参考。

Abstract

[Objective] The eastward-moving southwest vortex is an important weather system affecting drought and flood variations in the Yangtze River Delta region of China. However, its specific impact on the Yangtze River Delta region remains incompletely understood. The aim is to investigate the detailed characteristics of regional heavy rainfall in the Yangtze River Delta influenced by eastward-moving southwest vortex. [Methods] Using the “Southwest Vortex Almanac”, CN05. 1 gridded precipitation data, and ERA5 reanalysis data, statistical analysis and case comparisons were conducted on the movement characteristics of southwest vortices and the characteristics of regional heavy rainfall in the Yangtze River Delta region caused by eastward-moving southwest vortices. [Results] The result showed that from 2012 to 2019, a total of 716 southwest vortices were generated. The primary movement path of southwest vortices exiting their source region was eastward. Eastward-moving southwest vortices accounted for approximately 30% of the total cases generated, contributing more than 10% of the total precipitation in the Yangtze River Delta region. [Conclusion] The findings indicate that the eastward movement and development of southwest vortices are favored when the East Asian Trough and the Northwestern Pacific Subtropical High are relatively strong. The impact of eastward-moving southwest vortices on precipitation in the Yangtze River Delta region exhibits significant spatial heterogeneity, with the maximum contribution mainly located in the western part of the region. The areas of heavy precipitation are generally consistent with the movement paths of the southwest vortices, the intensity of the southwesterly warm and moist airflow on the southern side of the vortices, and the locations of strong upper-and lower-level convergence and divergence zones. The specific characteristics of heavy rainfall in the Yangtze River Delta region influenced by eastward-moving southwest vortices, including the large-scale circulation patterns and meso-and micro-scale dynamic configurations, demonstrate their unique impact on heavy rainfall events in this region. These findings provide theoretical references for the operational forecasting of heavy rainfall in the Yangtze River Delta region potentially caused by eastward-moving southwest vortices.

关键词

西南低涡 / 东移型 / 暴雨 / 统计分析 / 长三角地区 / 环流形势 / 动力分析 / 水汽诊断

Key words

southwest vortex / eastward-moving / heavy rainfall / statistical analysis / Yangtze River Delta region / circulation pattern / dynamic analysis / moisture diagnostic

基金资助

国家自然科学基金项目(42505020)

上海市气象局科技人才类项目(KJRC202403)

上海市气象局科技人才类项目(KJRC202411)

中国气象局创新发展专项(CXFZ2024J001)

中国气象局气象能力提升联合研究专项(23NLTSZ002)

中国气象局青年创新团队(CMA2023QN06)