Research on a hailstorm process in Chongqing based on multi-source observation data

doi:10.11755/j.issn.1006-7639(2024)-04-0598

Abstract

Abstract:

In order to understand the thermodynamic evolution characteristics of the convective system before and after the occurrence of hailstorm, and strengthen the application of new detection data in hailstorm monitoring and early warning, a strong hailstorm weather process occurring in the western of Chongqing in the early morning of April 18, 2014 was analyzed by using the observation data of microwave radiometer, wind profiler radar and Doppler radar. The results show that the hailstorm process was a typical strong convective weather forced by low-level warm advection, and the radar echo overhanging characteristics and radial velocity convergence were obvious. Before the occurrence of the hailstorm, the temperature and humidity retrieved by microwave radiometer data increased significantly. From 1.0 to 3.0 hours before the occurrence of hailstorm, K index, 850 hPa and 500 hPa pseudo-equivalent potential temperature differenc (θ_se850-500), CAPE (Convective Available Potential Energy), vertical wind shear from 0 to 3 km (SHR_0-3) etc. increased significantly with time. The atmospheric refractive index structure constant (Cn²) increased to its peak within 0.2 to 0.5 hours before the occurrence of hailstorm, and the vertical velocity observed by wind profile radar in middle and lower layers, fluctuated significantly with height. The commonness of the parameters of multiple hail processes show that the brightness temperature of 25.00 GHz, Cn² and the area of atmospheric refractive index structure constant (S_Cn2) of microwave radiometer had a significant increase trend within half hour before the occurrence of hail, and S_Cn2 was greater than the threshold of -500 dB·km within 10 minitutes before the occurrence of hailstorm. The vertical integral liquid water and the vertical velocity difference from the ground to the high altitude reached the maximum when the hail fell on the ground, and the Cn² jumped to the threshold value of -120 dB in the middle and low layers. All the characteristics mentioned above have a good indication for identifying the occurrence of hail.

Key words: “4.18” hailstorm, microwave radiometer, wind profile radar, instability parameters

摘要：

为认识风雹发生前后对流系统的热动力演变特征，加强新型探测资料在风雹监测预警中的应用，利用微波辐射计、风廓线雷达、多普勒雷达等观测资料，对2014年4月18日凌晨发生在重庆西部地区的一次强风雹天气过程进行分析。结果表明：此次风雹过程为典型的低层暖平流强迫类强对流天气，雷达回波悬垂特征和径向速度辐合明显。风雹发生前，微波辐射计反演的温湿度跃增明显，风雹发生前1.0~3.0 h，K指数、850 hPa与500 hPa假相当位温差（θ_se850-500）、对流有效位能（Convective Available Potential Energy， CAPE）、0~3 km垂直风切变（Vertical Wind Shear，SHR_0-3）等指数随时间临近明显递增，大气折射率结构常数（Cn²）在风雹发生前0.2~0.5 h达到波峰，风廓线雷达显示中低层的垂直速度随高度波动较大；多次风雹过程的参数共性显示，风雹发生前0~0.5 h，微波辐射计25.00 GHz亮温、Cn²和大气折射率结构常数面积（ $S C n 2$ ）都有明显增加趋势，风雹发生前0~10 min， $S C n 2$ 均大于-500 dB·km阈值。观测站降雹时，垂直积分液态水和地面到高空的垂直速度差均达到最大，Cn²在中低层跃增大于阈值-120 dB。以上特征对识别风雹的发生有较好指示意义。

关键词: “4·18”风雹, 微波辐射计, 风廓线雷达, 不稳定参数

CLC Number:

P412

ZOU Qian, ZUO Chunyan, WU Zhengqian, ZHAI Danhua, MU Rong. Research on a hailstorm process in Chongqing based on multi-source observation data[J]. Journal of Arid Meteorology, 2024, 42(4): 598-610.

邹倩, 左春艳, 吴政谦, 翟丹华, 牟容. 基于多源观测资料研究重庆地区一次风雹过程[J]. 干旱气象, 2024, 42(4): 598-610.

Figures/Tables 13

Fig.1 The temperature profile （a） and water vapor density profile （b） from radiosonde and retrieved by microwave radiometer data and their average errors （c） at Shapingba Station from March to August 2014 （The error bars represent the standard deviation σ， and the line segment length is 2 σ. the same as below）

Fig.2 The evolution of reflectivity factors on the elevation of 0.5° （the left）， 4.3° （the middle） and average radial velocity on the elevation of 0.5° （the right） of Yongchuan radar in Chongqing from 23：44 April 17 to 00：02 April 18， 2014 （The black circle is the position of Zengjia in Shapingba， the azimuth of Zengjia relative to Yongchuan radar is 52°， and the distance is 57 km）

Fig.3 The variation of different meteorological elements observed by microwave radiometer and the measured minute-by-minute precipitation at Shapingba Station in Chongqing from 18：00 on 17 to 02：00 on 18 April 2014

Fig.4 The vertical profiles of temperature （a）， humidity （b） and liquid water content （c） observed by microwave radiometer at Shapingba Station in Chongqing at 00：00， 00：05 and 00：10 April 18， 2014

Fig.5 The brightness temperature observed by microwave radiometer and simulated brightness temperature at 20：00 on 17 April 2014 （a）， the average brightness temperature from 00：04 to 00：07 on 18 April 2014 and the 24 h average brightness temperature of K-band water vapor channel （b）， and V-band oxygen channel （c） at Shapingba Station in Chongqing

Fig.6 The variation of horizontal wind field of windprofile radar with time at Shapingba Station in Chongqing from 18:00 on 17 to 02:00 on 18 April 2014 (a) and from 23:00 on 17 to 01:00 on 18 April 2014 (b) (Unit: m·s-1) (The color shaded indicates vertical wind field)

Fig.7 Vertical profile of vertical velocity and atmospheric refractive index structure constant （Cn2） of wind profile radar before and after hail at Shapingba Station on April 18， 2014 （a） hail time （00：05 on 18），（b） before the hail （23：55 on 17），（c） before the hail （00：00 on 18），（d） after the hail （00：10 on 18）

Tab.1 Comparison of some environment parameters calculated by microwave radiometer and wind profile radar data with radiosonde observations at 20：00 on April 17，2014

项目	K指数/℃	TT/℃	SI/℃	θ_se850-500/℃	CAPE/（J·kg^-1）	SHR_0-6/（m·s^-1）
探空观测	40.00	48.80	-3.20	25.20	2 042.00	21.30
探空时间内微波辐射计和风廓线雷达计算的平均值	42.70	51.80	-3.70	19.50	1 860.00	27.50
探空时间内微波辐射计和风廓线雷达计算的均方根误差	0.90	0.98	0.52	1.13	167.28	2.33
春季重庆地区风雹阈值	34.00	50.00	-1.90	16.00	872.00	14.00

Fig.8 The 30 min average value and variation ratio of 12 thermal and dynamic instability parameters calculated by microwave radiometer and wind profile radar data in 5 hours before the occurrence of hailstorm

Fig.9 The variation of the 5 min average value of brightness temperature （a）， atmospheric refractive index structure constant （b） and the area of atmospheric refractive index structure constant （c） in 2 hours before the occurrence of hailstorm

Tab.2 The weather phenomena during main periods of the three hailstorm processes in Chongqing

日期	主要时段	风雹中心区天气现象	冰雹最大直径/mm	风雹发生前5 h 观测站降雨情况	风雹中心离观测站距离/km
2014-08-04	16：30—17：00	风雹、小雨	20	无降雨	8.8
2017-05-10	23：30—次日00：30	雷暴、风雹、短时强降雨	<10（随降随化）	无降雨	19.9
2018-05-05	19：30—20：30	风雹、小到中雨	<10	弱降雨	29.4

Fig.10 Variation of 30 min average value of environmental parameters within 5 hours before the three hailstorm processes

Fig.11 The variation of brightness temperature of 25.00 GHz （a） and 58.80 GHz （b）， atmospheric refractive index structure constant （c） and the area of atmospheric refractive index structure constant （d） in 2 hours before the occurrence of the three hailstorm processes

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