"21·11"极端暴雪过程多系统结构演变及热动力机制

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中文摘要：利用多种实时观测资料和ERA5再分析资料，对造成2021年11月6-8日华北、东北极端暴雪过程多系统的结构特征及热动力机制进行分析。结果表明:此次过程先后由500 hPa高空横槽、河套西风槽及高空冷涡接力影响，其上空的高空急流不断加强并呈现"S"型弯曲，同时低空偏南风急流形成与加强，并在东北地区与高空急流耦合。此次过程阶段性特征明显，其影响系统的结构特征和水汽输送存在差异。回流冷锋形成的冷垫锋面较为浅薄，暖湿气流在其上倾斜上升。寒潮冷锋则较为陡立，上升气流随高度西倾。而锋面气旋结构较为深厚直立，使得气流呈垂直上升运动。随着斜压强迫的不断增强，850 hPa切变线由准东西向分布转为南北向分布，再演变为低涡切变结构。对应的水平涡度由弱转强，其上空正涡度垂直分布也逐渐加强，由弱倾斜上升运动逐步演变为较强垂直上升运动区，并在系统东侧形成次级环流下沉支。此次过程的发生发展与锋生作用密切相关，降雪落区和强度与锋区走向及锋生函数大小较为一致。假相当位温锋区在降雪3个阶段逐渐加强，垂直锋区和低层锋生函数由倾斜状态演变为近乎直立结构;湿位涡诊断表明，3个阶段降雪落区均发生在湿位涡正压项＞0而斜压项＜0配置的区域，条件性对称不稳定是此次过程的主要动力机制。

外文标题：Multi-System Structure Evolution and Thermodynamic Mechanism of the Extreme Snowstorm During 6-8 November 2021

外文摘要：The structure characteristics and thermodynamic mechanism of the extreme snowstorm in the Northeast and North China during 6-8 November 2021 are analyzed with multiple observations and the fifth-generation European Centre for Medium-Range Weather Forecasts(ECMWF)reanalysis data.The results show that this process was successively affected by the upper transversal trough,the westerly trough in Hetao Plain and the upper cold vortex at 500 hPa.The high-level jet over the influence system was gradually strengthened,featuring an"S"curve.Meanwhile,the southern low-level jet was formed,strengthened,and coupled with the high-level jet in Northeast China.The influence systems of this process emanated distinct phased characteristics with significant differences in the structure characteristics and water vapor transport.The cold surface area formed by the return-flow cold front was relatively shal-low,and the warm moisture flow was rising obliquely along it.The cold front was relatively steep with a westward tilting updraft,while the ground cyclone front was deep and vertical,making the air flow ascend vertically.With the enhancement of baroclinic forcing,the 850 hPa shear line turned to north-south distri-bution from quasi-east-west direction and then evolved into a low vortex shear structure.Correspondingly,the horizontal vorticity changed from weak to strong,and the overlying vertical distribution of positive vorticity gradually strengthened,featured with a weak slantwise updraft evolving into a strong vertical as-cending zone and a secondary circulation sinking branch forming on the east of the system.Frontogenesis fostered this extreme snowstorm.The pseudo-equivalent potential temperature front area gradually strengthened in the three stages of snowfall,and the vertical front area developed from an inclined state in-to a nearly vertical structure.The snowfall area was consistent with the evolution of the front area and the snowfall intensity was proportional to the magnitude of frontogenesis function.The diagnosis of the moist potential vorticity shows that all the snowfall areas in the three stages occur in the configuration region where the barotropic(baroclinic)term is greater(less)than 0.Conditional symmetric instability is the main dynamic mechanism of this extreme snowstorm.

外文关键词：

multi-system structureground cyclonebaroclinic forcingconditional symmetric instabilitydynamic frontogenesis

作者：

齐道日娜、何立富、张乐英

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作者单位：

中国气象局气象干部培训学院,北京 100081

国家气象中心,北京 100081

江苏省南方现代林业协同创新中心/南京林业大学生物与环境学院,南京 210037

关键词：

多系统结构地面气旋斜压强迫条件对称不稳定动力锋生

基金：

国家自然科学基金项目国家自然科学基金项目国家自然科学基金国际合作与交流项目2023年复盘总结专项2023年干部学院重点科研项目

项目编号：

420050334227501342261144002FPZJ2023-1672023CMATCZDIAN05

出版年：

2024

DOI：

10.7519/j.issn.1000-0526.2023.091401

气象

国家气象中心

气象

CSTPCD北大核心

影响因子：2.337

ISSN：1000-0526

年,卷(期)：2024.50(1)

参考文献量32