Causes analysis of an extreme warm-sector rainstorm in Beijing-Tianjin-Hebei region

doi:10.11755/j.issn.1006-7639-2026-01-0115

Abstract

Abstract:

With the increasing frequency of warm-sector heavy rain events in North China, it is of great significance to study the occurrence and evolution mechanism of mesoscale convective systems during warm-sector heavy rain processes to improve the forecasting ability of warm-sector heavy rain. This research conducts a numerical simulation on the circulation background, thermodynamic structure, and moisture transportation characteristic of an extreme warm-sector rainstorm event in the Beijing-Tianjin-Hebei region using the high-resolution (3 km) WRF (Weather Research & Forecasting Model) mesoscale model, combined with the 0.25°×0.25° reanalysis data from the fifth generation global climate reanalysis dataset (ERA5) of the European Centre for Medium-Range Weather Forecasts, along with conventional and radar observation data for rapid assimilation updates. The results demonstrate that: (1) The high-resolution WRF model, which has been rapidly updated with assimilated observational data, can effectively simulate this warm-sector rainstorm process, accurately representing the radar echo characteristics and propagation mechanisms of meso-small scale systems, verifying the model’s capability to characterize key processes of warm-sector rainstorms. (2) The dynamic characteristics of this process are characterized by synergy of “three jet streams”: the 950 hPa ultra-low-level jet, the 850 hPa low-level jet, coupled with the strong divergence in the exit region on the right side of the 200 hPa upper-level jet, forming a vertical suction structure. The phased evolution characteristics of the low level (the establishment of the ultra-low-level jet, the fluctuation of the low-level jet intensity, the enhancement and maintenance of the low-level jet) are the key factors for the occurrence and maintenance of the heavy precipitation process. (3) Enhanced upward motion induced by low-level jet intensity fluctuation and convergence continuously lifts warm-moist airflow, promoting water vapor condensation and precipitation. Meanwhile, downward intrusion of mid-level weak dry air into high warm-moisture areas triggers the release of unstable energy, further intensifying the process. (4) The low-level high-humidity environment provides abundant water vapor conditions for the heavy rain. With the strengthening of the low-level southeast jet stream, water vapor from the Bohai Bay continuously flow into the Beijing-Tianjin-Hebei region. The strong accumulation of water vapor, combined with powerful dynamic conditions, is the main cause of local short-term heavy precipitation.

Key words: warm-sector rainstorm, low-level jet, upper-level jet, numerical simulation

摘要：

随着华北暖区暴雨事件增多，研究暖区暴雨过程中尺度对流系统发生及演变机制对提升暖区暴雨预报能力具有重要意义。基于高分辨率（3 km）WRF（Weather Research & Forecasting Model）中尺度模式，结合欧洲中期天气预报中心第五代全球气候再分析数据集（ERA5）0.25°×0.25°再分析资料，利用常规、雷达观测数据快速更新同化，对京津冀地区一次极端暖区暴雨过程的环流背景、热动力结构、水汽输送特征进行数值模拟研究。结果表明：（1）经快速更新同化观测资料的高分辨率WRF模式能较好地模拟此次暖区暴雨过程，对中小尺度系统回波及传播机制有很好体现，验证了模式对暖区暴雨关键过程的表征能力；（2）此次过程动力特征表现为“3支急流”协同作用：950 hPa超低空急流、850 hPa低空急流配合200 hPa高空急流右侧出口区的强辐散，形成垂直抽吸结构。低层阶段性演变特征（超低空急流的建立-低空急流强度脉动-低空急流的增强与维持）是强降水过程发生并维持的关键因素。（3）在低空急流强度脉动及辐合造成的上升运动增强下，暖湿气流不断被抬升，促进水汽凝结并产生降水。同时中层弱干空气向下侵入高暖湿区，触发不稳定能量释放对此次过程也有加强作用。（4）低层高湿环境为暴雨提供了充沛水汽条件，随着低空东南急流的增强，促使来自渤海湾的水汽不断汇入京津冀地区。强水汽聚集再配合强有力的动力条件，是局地短时强降水发生的主要原因。

关键词: 暖区暴雨, 低空急流, 高空急流, 数值模拟

CLC Number:

P456
P458

DONG Qiru, WANG Ying, LI Yinghua, YANG Xu, LIANG Kangzhuang. Causes analysis of an extreme warm-sector rainstorm in Beijing-Tianjin-Hebei region[J]. Journal of Arid Meteorology, 2026, 44(1): 115-125.

董琪如, 王莹, 李英华, 杨旭, 梁康壮. 京津冀地区一次极端暖区暴雨成因分析[J]. 干旱气象, 2026, 44(1): 115-125.

Figures/Tables 10

Tab.1 Main parameterization schemes of the model

物理方案	选项设置
微物理方案	新Tompson
近地面方案	MM5相似理论
陆面方案	Noah
行星边界层方案	ACM2 PBL
积云参数化方案	Kain-Fritsch（d02区无）
长波辐射方案	RRTM
短波辐射方案	Dudhia

Fig.1 The 3 km inner forecast area of rapid update assimilation system （The shaded for terrain height，Unit： m）

Fig.2 The 24 h accumulative precipitation （R） from 00：00 August 12 to 00：00 August 13，2020 （Unit： mm）

Fig.3 The 500 hPa geopotential height （contour lines，Unit： dagpm），wind field （arrow vectors，Unit： m·s-1） and 200 hPa high-level jet （the shaded，Unit： m·s-1）（a，b），and 850 hPa geopotential height （contour lines，Unit： dagpm），wind field （arrow vectors，Unit： m·s-1），and low-level jet （ the shaded，Unit： m·s-1）（c，d） at 06：00 （a，c） and 15：00 （b，d） August 12，2020

Fig.4 Distribution of observed （a，c） and simulated （b，d） accumulated precipitation at 10：00 （1 hour）（a，b） and from 09：00 to 15：00 （6 hours）（c，d） August 12，2020 （Unit： mm）（The AB line denotes the core region of the 6-hour accumulated precipitation maximum along the orientation of the rainfall belt）

Fig.5 Simulated maximum radar reflectivity （Unit： dBz） at different forecasting time from 10：00 to 15：00 on August 12，2020 （The black box represents the mesoscale convective system that influenced the rainstorm）

Fig.6 The simulated 850 hPa wind field （wind vectors，Unit： m·s-1） and divergence （the color shaded，Unit： 10-4 s-1） at 11：00 （a），13：00 （b），15：00 （c） on August 12，2020 （The black box indicates the area of strong convergence，and the ellipses represent the convergence point of the wind field）

Fig.7 The simulated vertical cross sections of wind vectors （wind vectors，Unit： m·s-1），vertical velocity （the color shaded，Unit： m·s-1） and wind velocity （isolines，Unit： m·s-1） along the AB line of the Fig.4（d） from 10：00 to 15：00 on August 12，2020 （a）10：00，（b）11：00，（c）12：00，（d）13：00，（e）14：00，（f）15：00 （The red box indicates the area where the low-level easterly wind is gradually strengthening，and the purple box indicates the intensity pulsation zone of the low-level jet）

Fig.8 The simulated vertical cross sections of potential pseudo-equivalent temperature （isolines，Unit： K） and divergence （the color shaded，Unit： 10-4s-1） along the AB line of the Fig.4（d） at 11：00 （a），13：00 （b），15：00 （c） on August 12，2020

Fig.9 The simulated water vapour fux divergence （the color shaded，Unit： 10-6 g·cm-2·hPa-1·s-1），wind field （wind vectors，Unit： m·s-1），specific humidity （green isolines，Unit： g·kg-1） and terrain height （the area filled with line segments，Unit： m） at 950 hPa at 11：00 （a），13：00 （b），15：00 （c） on August 12，2020 （The black box denotes the region of intense water vapor convergence）

References 35

[1]	谌芸, 陈涛, 汪玲瑶, 等, 2019. 中国暖区暴雨的研究进展[J]. 暴雨灾害, 38(5): 483-493.
[2]	谌芸, 吕伟绮, 于超, 等, 2018. 北方一次暖区大暴雨降水预报失败案例剖析[J]. 气象, 44(1): 15-25.
[3]	谌芸, 孙军, 徐珺, 等, 2012. 北京721特大暴雨极端性分析及思考(一)观测分析及思考[J]. 气象, 38(10):1 255-1 266.
[4]	段伯隆, 张文龙, 刘海文, 等, 2017. 北京“7·21”特大暴雨过程暖区降水和锋面降水的时空分布特征[J]. 暴雨灾害, 36(2): 108-117.
[5]	段宇辉, 孙云, 刘昊野, 等, 2025. 一次华北暖区暴雨的边界层环境条件分析[J]. 暴雨灾害, 44(2): 156-166.
[6]	高守亭, 周玉淑, 冉令坤, 2018. 我国暴雨形成机理及预报方法研究进展[J]. 大气科学, 42(4): 833-846.
[7]	何立富, 陈涛, 孔期, 2016. 华南暖区暴雨研究进展[J]. 应用气象学报, 27(5): 559-569.
[8]	黄美金, 俞小鼎, 林文, 等, 2022. 福建沿海冷锋前暖区和季风槽大暴雨环境背景与对流系统特征[J]. 气象, 48(5): 605-617.
[9]	黄士松, 1986. 华南前汛期暴雨[M]. 广州: 广东科技出版社:9-10.
[10]	雷蕾, 邢楠, 周璇, 等, 2020. 2018年北京“7·16”暖区特大暴雨特征及形成机制研究[J]. 气象学报, 78(1): 1-17.
[11]	李向红, 庞传伟, 梁维亮, 等, 2015. 孟加拉湾旺盛对流作为广西连续暴雨的前兆信号特征分析[J]. 气象, 41(11):1 383-1 389.
[12]	祁璇, 平凡, 沈新勇, 2021. 云微物理对一次吉林暖区降水过程的影响[J]. 大气科学, 45(5): 943-964.
[13]	沈晓玲, 冯博, 李锋, 等, 2024. 一次弱天气背景下浙江局地暖区暴雨成因分析[J]. 气象, 50(2): 170-180.
[14]	孙继松, 何娜, 王国荣, 等, 2012. “7·21”北京大暴雨系统的结构演变特征及成因初探[J]. 暴雨灾害, 31(3): 218-225.
[15]	孙建华, 赵思雄, 傅慎明, 等, 2013. 2012年7月21日北京特大暴雨的多尺度特征[J]. 大气科学, 37(3): 705-718.
[16]	孙密娜, 王秀明, 胡玲, 等, 2018. 华北一次暖区暴雨雷暴触发及传播机制研究[J]. 气象, 44(10):1 255-1 266.
[17]	徐珺, 杨舒楠, 孙军, 等, 2014. 北方一次暖区大暴雨强降水成因探讨[J]. 气象, 40(12):1 455-1 463.
[18]	杨晓亮, 杨敏, 段宇辉, 等, 2021. 京津冀一次暖区大暴雨的成因分析[J]. 暴雨灾害, 40(5): 455-465.
[19]	俞小鼎, 2012. 2012年7月21日北京特大暴雨成因分析[J]. 气象, 38(11):1 313-1 329.
[20]	张芹, 苏莉莉, 张秀珍, 等, 2019. 山东一次暖区暴雨的环境场特征和触发机制[J]. 干旱气象, 37(6): 933-943.
[21]	张芹, 王洪明, 张秀珍, 等, 2018. 2017年山东雨季首场暖区暴雨的特征分析[J]. 高原气象, 37(6):1 696-1 704.
[22]	周玉淑, 刘璐, 朱科锋, 等, 2014. 北京“7·21”特大暴雨过程中尺度系统的模拟及演变特征分析[J]. 大气科学, 38(5): 885-896.
[23]	DU Y, CHEN G X, HAN B, et al, 2020. Convection initiation and growth at the coast of South China. Part II: Effects of the terrain, coastline, and cold pools[J]. Monthly Weather Review, 148(9):3 871-3 892. DOI URL
[24]	DU Y, CHEN G X, 2018. Heavy rainfall associated with double low-level jets over Southern China. Part I: Ensemble-based analysis[J]. Monthly Weather Review, 146(11):3 827-3 844. DOI URL
[25]	LUO Y L, ZHANG R H, WAN Q L, et al, 2017. The southern China monsoon rainfall experiment (SCMREX)[J]. Bulletin of the American Meteorological Society, 98(5): 999-1 013. DOI URL
[26]	MAO J H, PING F, YIN L, et al, 2018. A study of cloud microphysical processes associated with torrential rainfall event over Beijing[J]. Journal of Geophysical Research: Atmospheres, 123(16):8 768-8 791. DOI URL
[27]	MENARD R D, FRITSCH J M, 1989. A mesoscale convective complex-generated inertially stable warm core vortex[J]. Monthly Weather Review, 117(6):1 237-1 261. DOI URL
[28]	SUN J H, ZHANG Y C, LIU R X, et al, 2019. A review of research on warm-sector heavy rainfall in China[J]. Advances in Atmospheric Sciences, 36: 1 299-1 307.
[29]	WANG H, LUO Y L, JOU B J, 2014. Initiation, maintenance, and properties of convection in an extreme rainfall event during SCMREX: Observational analysis[J]. Journal of Geophysical Research: Atmospheres, 119(23):13 206-13 232.
[30]	WU M W, LUO Y L, 2016. Mesoscale observational analysis of lifting mechanism of a warm-sector convective system producing the maximal daily precipitation in China mainland during pre-summer rainy season of 2015[J]. Journal of Meteorological Research, 30(5): 719-736. DOI URL
[31]	ZENG W X, CHEN G X, DU Y, et al, 2019. Diurnal variations of low-level winds and precipitation response to large-scale circulations during a heavy rainfall event[J]. Monthly Weather Review, 147(11):3 981-4 004. DOI URL
[32]	ZHANG L, MA X Y, ZHU S P, et al, 2022. Analyses and applications of the precursor signals of a kind of warm sector heavy rainfall over the coast of Guangdong, China[J]. Atmospheric Research, 280: 106425. DOI:10.1016/j.atmosres.2022.106425.
[33]	ZHANG M R, MENG Z Y, 2018. Impact of synoptic-scale factors on rainfall forecast in different stages of a persistent heavy rainfall event in South China[J]. Journal of Geophysical Research: Atmospheres, 123(7):3 574-3 593. DOI URL
[34]	ZHONG L Z, MU R, ZHANG D L, et al, 2015. An observational analysis of warm-sector rain fall characteristics associated with the 21 July 2012 Beijing extreme rainfall event[J]. Journal of Geophysical Research: Atmospheres, 120(8):3 274-3 291. DOI URL
[35]	ZHOU C H, LI Y Q, 2024. Dynamic and thermodynamic characteristics of warm-sector rainstorms caused by the southwest China vortex in Sichuan basin[J]. Theoretical and Applied Climatology, 155:7 095-7 108. DOI