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一次伴随高架雷暴的极端暴雪不稳定机制分析

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  • 万方数据
  • 维普
利用常规观测资料、闪电定位监测、雷达资料和ERA5再分析资料等，分析了2023年12月14日山东地区的一次"雷打雪"天气过程的不稳定机制，利用锋生函数、假相当位温的密集区和地面温度的变化特征等，确定了地面冷锋的位置，结合物理过程的触发和不稳定机制，给出了高架对流暴雪的概念模型。结果表明:雷暴和强降雪出现在地面冷锋后部，低空有深厚稳定的冷垫，逆温层之上存在强盛的暖湿空气，具有产生高架雷暴的环境。暴雪发生期间，存在对流-对称不稳定机制，且对称不稳定和位势不稳定存在于不同层次上:对称不稳定主要位于700 hPa以下，当暖湿气流沿低层冷垫强迫爬升，倾斜对流发展;而位势不稳定位于700～500 hPa，是伴随中低层西南急流的推进逐步建立的。当对称不稳定导致的倾斜对流发展到700～500 hPa层次时，位势不稳定能量得以释放，发展出深厚强烈的垂直对流。位势不稳定的建立与700～500 hPa上20 m·s-1风速前沿的向北推进在时间上具有高度的一致性，超前于最强降雪和雷电，提前1～2 h。高架雷暴的触发除了低层冷垫的动力抬升外，还与中层700～500 hPa附近风速的增强有关，700～500 hPa风速增强后，槽前正涡度平流加强，上升气流发展，进而触发对流，造成强降雪和强烈、高频的雷电活动。尽管本次高架雷暴强降雪时段的回波主要集中在20～35 dBz，但回波顶高超过了-30℃层高度，35 dBz回波伸展到达-10℃层高度之上，仍需高度关注冬季雷电的发生。
Analysis of Instability Mechanism of an Extreme Blizzard Accompanied by Elevated Thunderstorms
Based on conventional observation,three-dimensional lightning locator,Doppler weather radar and ERA5 reanalysis data,the characteristics of a convective event on 14 December 2023 in Shandong Province are analyzed.The position of the ground cold front is determined by using the frontogenesis func-tion,the dense zone of pseudo-equivalent temperature,and the temperature variation.A conceptual model diagram of the physical process is proposed.The results show that thunderstorm and heavy snowfall oc-curred at the rear of the ground cold front,with a deep and stable cold cushion in the low altitude,and strong warm and humid air above the temperature inversion layer,forming the environment for elevated thunderstorm.During the blizzard,there was convective-symmetric instability,and the symmetric insta-bility and potential instability were at different levels.The symmetric instability was below 700 hPa,and the tilting convection developed during the forced uplift of warm and humid air flow along the low-level cold cushion.The potential instability was located at 700-500 hPa and was established with the advancement of the southwest jet.When the tilting convection caused by symmetric instability reached a level of 700-500 hPa,the energy of potential instability was released,leading to the development of deep and strong vertical convection.The establishment of potential instability was consistent with the northward advance of 20 m·s-1wind speed at 700-500 hPa,which was 1-2 h ahead of the heaviest snowfall and thunder.The triggering of elevated thunderstorm was not only related to the uplift of the low-level cold cushion,but also to the enhancement of wind near 700-500 hPa in the middle layer.With the increase of wind speed at 700-500 hPa,the positive vorticity advection was strengthened,and then the upward airflow fur-ther developed,causing severe snowfall and high-frequency lightning.The convective property of this ele-vated convection was not typical and the echo intensity was mainly concentrated in 20-35 dBz,but the echo top height exceeded the-30℃ layer height and the 35 dBz echo extended above the-10℃ layer height.Therefore,it is still necessary to pay close attention to the occurrence of lightning in winter.

thundersnowextreme blizzardelevated thunderstormconvective-symmetric instability

万夫敬、李博、罗江珊、侯淑梅、庞华基

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青岛市气象局,青岛 266003

山东省菏泽市气象局,菏泽 274100

山东省气象台,济南 250031

雷打雪 极端暴雪 高架雷暴 对流-对称不稳定

山东省自然科学基金项目山东省自然科学基金项目山东省自然科学基金项目山东省预报员专项山东省预报员专项淮河流域基金项目山东省气象局创新团队项目青岛市气象局重点课题

ZR2021MD010ZR2021MD062ZR2023MD118SDYBY2019-07SDYBY2017-06HRM201807SDCXTD2023-12023qdqxz02

2024

10.7519/j.issn.1000-0526.2024.071202

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(9)