Diagnostic analysis of trigger and maintenance mechanism associated with a rainstorm over Liaodong Peninsula

doi:10.11755/j.issn.1006-7639-2025-03-0435

Abstract

Abstract:

The heavy precipitation occurred in the northeastern region of Liaodong Peninsula from 20:00 on 3 to 14:00 on 5 August 2017, with the daily rainfall breaking historical records. Based on observations from automatic weather stations, radiosonde and Doppler weather radars, FY-2G temperature of brightness blackbody product, and European Centre for Medium-Range Weather Forecasts ERA5 reanalysis data, diagnostic analyses are made on the torrential rain processes in Liaodong Peninsula during 3-5 August 2017. The synoptic background, mesoscale environment and triggering mechanism of the mesoscale convective systems (MCSs) are focused. The results show there were two stages of this extreme rainstorm and it was influenced by upper trough, low-level shear line, the warm and moist flows in the border of the subtropical high near Japan, the intrusion of north cold-dry current, and the surface convergence line. The differences in short-term heavy precipitation between the two stages are significant, which is closely related to the low-level moisture, vertical shear of the environmental wind, and the intensity of frontogenesis. When there is abundant low-level moisture, large vertical shear of the horizontal wind, and strong frontogenesis, there is more precipitation. Frontogenesis process in the lower layer and the coupling dynamic structure of positive vorticity center and the divergence center over Liaodong Peninsula, further uplift the air, thus enable those initial convective cells to move northeastward alongside the shear line, to merge and develop, promoting higher organization and more stronger of the convection system. As shown on the surface wind field in Liaodong Peninsula, there were two north-south convergence lines and at their meeting location, convective cells merged and intensified, which was the main cause of extreme short-term heavy precipitation (hourly precipitation ≥50 mm). The surface convergence line was formed by the cold-dry current from the northeastern of Liaodong Peninsula spreading southwestward and the southerly airflow on its eastern side. In addition, the terrain blocking effect and the cold pool effect caused by heavy precipitation promoted the southward extension of the northeasterly or northerly air flow, and the backward propagation of convective cells, which was conducive to the maintenance and intensification of heavy precipitation.

Key words: rainstorm, Liaodong Peninsula, shear line, cold dry air, surface convergence line

摘要： 2017年8月3日20：00—5日14：00（北京时）辽东半岛东北部发生了一次强降水过程，其日降水量突破历史极值。利用地面自动气象站资料、探空资料、多普勒雷达资料、FY-2G卫星云顶亮温数据、欧洲中期天气预报中心ERA5再分析资料，对2017年8月3—5日辽东半岛大暴雨过程的天气形势、中尺度对流系统的发展过程及其触发机制进行诊断分析。结果表明：此次大暴雨过程分为两个强降水阶段，主要由高空槽、低层切变线、副热带高压边缘的暖湿气流、北方干冷空气和地面辐合线共同影响所致；两个阶段短时强降水差异较大，这与低层水汽、环境风垂直切变、锋生强度密切相关，低层水汽丰沛、水平风垂直切变较大、锋生较强时，降水较多；辽东半岛对流层低层的锋生过程、正涡度中心和辐合中心耦合的动力结构，进一步加强了抬升作用，促使对流系统组织化程度更高、强度更强；辽东半岛地面南北辐合线交汇处对流单体合并增强，是产生极端短时强降水（小时降水量≥50 mm）的主要原因，地面辐合线由辽东半岛东北部向西南扩散的干冷空气与其东侧偏南气流所形成；地形阻挡作用和强降水的冷池效应促使东北或偏北气流向南延伸，对流单体后向传播，利于强降水的维持和加强。

关键词: 大暴雨, 辽东半岛, 切变线, 干冷空气, 地面辐合线

CLC Number:

P445

LIANG Jun, JIA Xuxuan, ZHANG Shengjun, FENG Chengcheng, LI Tingting, CHENG Hang, LIU Xiaochu. Diagnostic analysis of trigger and maintenance mechanism associated with a rainstorm over Liaodong Peninsula[J]. Journal of Arid Meteorology, 2025, 43(3): 435-449.

梁军, 贾旭轩, 张胜军, 冯呈呈, 李婷婷, 程航, 刘晓初. 辽东半岛一次大暴雨过程触发和维持机制分析[J]. 干旱气象, 2025, 43(3): 435-449.

Figures/Tables 13

Fig.1 The distribution of rainfall amount in Liaodong Peninsula from 20:00 on 3 to 14:00 on 4 (a) and from 20:00 on 4 to 14:00 on 5 (b) August 2017 (Unit: mm)

Fig.2 The hourly precipitation at Shahekou (a), Taling (b) and Shihuiyao (c) stations from 14:00 on 3 to 11:00 on 4，Tongxing (d) and Donghualu (e) stations from 21:00 on 4 to 14:00 on 5 August 2017

Fig.3 The 500 hPa height fields （black solid lines， Unit： dagpm） and temperature fields （red dashed lines， Unit： ℃）， 200 hPa wind speed （the color shaded， Unit： m·s-1）at 20：00 on 3（a）and 20：00 on 4（c）August 2017；the 850 hPa wind fields （wind vectors， Unit： m·s-1） and water vapor flux fields （the color shaded， Unit： g·cm-1·hPa-1·s-1） at 02：00 on 4 （b） and 02：00 on 5 （d） August 2017 （The red solid dot indicates the TC centers of Noru， the black thick solid line is upper-level trough， the solid red line is the shear line； the red triangle shows Liaodong Peninsula， the same as below）

Fig.4 The distribution of TBB (the color shaded, Unit: ℃, TBB≤-15 ℃) from FY-2G satellite, 850 hPa water vapor flux divergence (purple dashed lines，Unit: 10-7 g·cm-2·hPa-1·s-1) and equivalent potential temperature（gray solid lines, Unit: K）at 02:00 (a) and 08:00 (b) on 4 August 2017 (The black thick solid lines are the shear lines, the same as below)

Fig.5 The distribution of TBB (the color shaded, Unit: ℃, TBB≤-15 ℃) from FY-2G satellite, 850 hPa water vapor flux divergence (purple dashed lines，Unit: 10-7 g·cm-2·hPa-1·s-1) and equivalent potential temperature（gray solid lines, Unit: K）at 02:00 (a) and 08:00 (b) on 5 August 2017

Tab.1 Convective available potential energy （CAPE）， convective inhibition energy （CIN）， total temperature （Tt）， lift condensation level （LCL）， K index， precipitable water （PW）， surface lifting index （LI）， ground pseudo-equivalent potential temperature （θse） and ground relative humidity （RH） calculated from sounding stations in the rainstorm area

时间	站点	CAPE/（J·kg^-1）	CIN/（J·kg^-1）	T_t/℃	LCL/hPa	K/℃	P_W/mm	LI	θ_se/K	RH/%
3日20：00	丹东	1 467.3	15.7	42	989	37	69	-3.9	361	94
	大连	893.1	6.7	47	975	42	63	-4.0	358	94
	荣成	1 193.9	2.0	44	978	39	74	-3.4	363	94
4日08：00	丹东	13.2	247.2	42	961	36	65	0.4	345	83
	大连	114.1	145.0	41	976	34	56	0.4	354	94
	荣成	663.4	0	41	992	40	78	-2.0	362	100
4日20：00	丹东	404.5	163.1	43	975	35	56	-1.2	345	83
	大连	1 175.9	0.1	41	991	39	59	-1.0	354	94
	荣成	1 222.8	24.2	43	980	40	64	-2.3	362	100
5日08：00	丹东	1.1	501.2	47	976	34	60	1.4	340	89
	大连	131.5	84.7	45	976	38	68	-1.6	354	94
	荣成	1 204.0	8.9	43	980	30	63	-4.3	363	94

Fig.6 The T-ln P charts at Shihuiyao Station at 00：00 on 4 （a）， Dalian Station at 03：00 on 4 （b） and Donghualu Station at 02：00 on 5（c）August 2017 （the red line for temperature curve， the green line for dew point curve， and the black line for state curve， the blue dotted line for the height of 0 ℃ layer）

Fig.7 The 10 m wind fields (wind vectors，Unit：m·s-1) and reflectivity at the elevation of 0.5° (the color shaded, Unit: dBZ) from Dalian radar at 21:00 （a）on 3, and 05:00 (b), 07:00 (c) on 4 August 2017 (The grey shaded area denotes topography, Unit: m; the red solid lines are for convergence lines, the same as below)

Fig.8 The 10 m wind fields (wind vectors， Unit：m·s-1) and reflectivity at the elevation of 0.5° (the color shaded, Unit: dBZ) from Dalian radar at 03：00 on 5 August （a），reflectivity at 0.5° elevation from Yingkou radar at 03:46 on 5 August (b) and the cross-section of reflectivity along the line in fig.8 (b) (Unit: dBZ) (c)

Fig.9 Vertical cross-sections along the line in fig.3 (b) （the shear line) for wind field (wind vectors, Unit: m·s-1), positive vorticity (solid lines) and divergence (the shaded areas for convergence areas) （Unit: 10-5s-1) (a)， for vertical speed （dotted lines, Unit: Pa· s-1)， specific humidity (the shaded areas， Unit: g·kg-1) and streamline of horizontal wind with vertical velocity (enlarged by 100 times) (b), the latitude-height cross sections along 123.1°E for relative humidity (the shaded areas， Unit: %) and the difference between temperature and dew-point (solid lines, Unit: ℃) (c)， for equivalent potential temperature (solid lines, Unit: K) and temperature advection (the shaded, Unit: 10-4 ℃·s-1) (d) at 02:00 on 4 August 2017 (○ denotes Shahekou Station， ▲ denotes Taling Station， ■ denotes Shihuiyao Station, and bold regions on the abscissa indicate the range of heavy precipitation，the same as below)

Fig.10 The longitude-height cross sections of frontogenesis function (Unit: 10-10 K·m-1·s-1) along 40.0°N at 02:00 on 4 (a) and along 39.8°N at 02:00 on 5 (b) August 2017

Fig.11 Vertical cross-sections along the line in fig.3 (b) （the shear line) for wind field (wind vectors, Unit: m·s-1), positive vorticity (solid lines) and divergence (the shaded areas for convergence areas) （Unit: 10-5s-1) (a)， for vertical speed （dotted lines, Unit: Pa·s-1)， specific humidity (the shaded areas for specific humidity≥12 g· kg-1) and streamline of horizontal wind with vertical velocity (enlarged by 100 times) (b), the latitude-height cross sections along 123.1°E for relative humidity (the shaded areas for relative humidity≥60%) and the difference between temperature and dew-point (solid lines, Unit: ℃) (c)， for equivalent potential temperature (solid lines, Unit: K) and temperature advection (the shaded, Unit: 10-4 ℃·s-1) (d) at 08:00 on 4 August 2017

Fig.12 Vertical cross-sections along the line in fig.3(d) （the shear line) for wind field (wind vectors, Unit: m·s-1), positive vorticity (solid lines) and divergence (the shaded areas for convergence areas) （Unit: 10-5s-1) (a)， for vertical speed （dotted lines, Unit: Pa·s-1)， specific humidity (the shaded areas for specific humidity≥12 g·kg-1) and streamline of horizontal wind with vertical velocity (enlarged by 100 times) (b), the latitude-height cross sections along 123.3°E for relative humidity (the shaded areas for relative humidity≥60%) and the difference between temperature and dew-point (solid lines, Unit: ℃) (c)， for equivalent potential temperature (solid lines, Unit: K) and temperature advection (the shaded, Unit: 10-4 ℃·s-1) (d) at 02:00 on 5 August 2017 (△ denotes Donghualu Station, □ denotes Tongxing Station, and bold regions on the abscissa indicate the range of heavy precipitation)

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