李新峰 陈博 梅珏

摘 要：利用实况资料、FNL再分析资料和客观预报资料，对2017年8月7日夜间上海空域雷暴天气过程的大尺度环流条件、中尺度触发机制进行天气学分析，讨论了客观预报在此次雷暴天气过程的可预报性问题。结果表明：此次上海空域雷暴天气过程的环流背景是东北冷涡底部的短波槽配合低层切变发展东伸，在副高北部形成了西南急流和上干下湿的不稳定层结，700 hPa露点锋南侵导致大面积强对流天气发生;影响上海地区的中-β尺度对流由近地面辐合线触发，配合高空不稳定能量的集聚和垂直风切变的增大，为对流风暴强烈发展提供条件;RUC因能快速吸收最新观测，对流范围预报效果在逐次循环中得到提高，但对上海空域的中-β尺度对流均为漏报，没有可预报性。Nowcasting能够提前1.5 h准确预报雷暴移动和强度变化。

关键词：雷暴;露点锋;辐合线;可预报性

中图分类号：P458.123;P457.5 文献标识码：A 文章编号：1003-5168（2021）22-0134-05

Abstract： A thunderstorm weather that seriously impacted air traffic on 7 August 2017 in Shanghai is studied. Using Doppler radar and FNL reanalysis data， synoptic weather conditions and mesoscale triggering mechanism for this event are analyzed， the predictability of forecasts in this thunderstorm weather process are discussed. Results are as follows： this event occurred under the condition of a deformation field. The short wave at the bottom of the northeast cold vortex extends eastward with the development of low-level shear， forming southwest jet and upper dry and lower wet unstable stratification in the north of the Western Pacific Subtropical High. The southward invasion of 700 hPa dew point front leads to a large area of strong convective weather; β-mesoscale convictive systems affecting Shanghai is triggered by the near surface convergence line， combined with large-scale uplift， which provides conditions for the strong development of convective storms; RUC can quickly absorb the latest observations， the convective range forecasting is improved in successive cycles， but β-mesoscale convictive systems in the Shanghai airspace is underreported. Nowcasting can accurately predict the movement rate and intensity of thunderstorms 1.5h in advance.

Keywords： thunderstorm;dew point front;convergence line;predictability

2017年8月7日19：30至8日02：00，上海終端区及虹桥机场、浦东机场出现了一次强雷暴天气过程。虹桥机场观测雷暴时间长达4 h，气温在2 h内骤降10 ℃，气压涌升4 hPa，最大小时雨量为25.9 mm。此次雷暴天气过程对民航上海终端区、虹桥机场和浦东机场的正常运行造成较大影响，均有较多航班延误和返航。

雷暴天气对民航飞行安全构成严重威胁，因其具有较小的时空尺度与剧烈的垂直运动，一直是航空气象预警的重要内容。长期以来，气象学家对雷暴发生发展的大、中尺度环境进行了广泛而深入的研究，发现了许多对风暴形成和结构演变具有重要影响的环境因素，如大气稳定度、高低空急流以及边界层辐合线等。……