EF3年江苏阜宁级龙卷分析与多波段雷达监测预警技术Ⅰ：天气分析与多波段雷达观测

Analysis of the 19 September 2023 EF3 Tornado in Funing,Jiangsu, and Multi-Band Radar Monitoring and Early Warning Techniques Ⅰ: Weather Analysis and Multi-Band Radar Observation

关键词:  “9.19”阜宁龙卷  EF3级  天气分析  多波段雷达  监测预警

Key words:  “9.19”Funing tornado  EF3-level intensity  weather analysis  multi-band radar  monitoring and early warning

摘要:

为深入认识江苏龙卷形成的机理，提高龙卷监测预警业务精准性。本文以江苏历史上9月份罕见的2023年9月19日阜宁EF3级龙卷(简称“9.19”阜宁龙卷)个例为切入点，从实况与灾情、天气背景和环境条件、多波段雷达协同观测及效果3方面展开讨论。(1)“9.19”阜宁龙卷是梅雨天气背景下发生的强龙卷事件。200hPa天气形势图出现气流分支和13.3μm通道红外云图有楔状云，是“9.19”阜宁龙卷深对流强迫和提前研判的重要指标。(2)热力和动力条件急剧变化表明大气的极不稳定和强劲的垂直上升运动，是触发强龙卷的重要潜势指标。CAPE跃增为2288.7J·kg-1，CIN骤减至0.2J·kg-1，LCL骤降为1005.0hPa(69m)，K指数骤升为40.2℃；0~1km风切变跃增为10.9m·s-1，0~3km风切变跃增为19.2m·s-1，0~6km风切变跃增为21.9m·s-1。(3)苏北多波段天气雷达网可提供最低探测高度100~350m为主的超低空资料，为龙卷监测预警提供了有力条件。“9.19”阜宁龙卷过程中苏北多波段天气雷达自适应观测效果较好，非人工干预下宝应XD(X-bandDual-polarizationWeatherRadar)雷达能合理地进行RHI(RangeHeightIndicater)自适应扫描，较完整地观测到龙卷超级单体的演变过程和垂直流场特征。尤其中低层反射率因子核(RC)和穹隆结构、中高层高悬回波、3~5km高度后侧“V”型缺口和穹隆的悬挂回波和中高层高悬回波之间的东北-西南走向的弱回波带演变特征，以及前侧入流的涡管环流场、高空下沉气流和后侧入流(急流)分流的流场特征。研究结果为江苏多波段天气雷达监测预警龙卷以及龙卷物理过程的客观认识提供了参考依据。

Abstract:

In order to deepen the objective understanding of the formation mechanisms of tornadoes in Jiangsu and improve the accuracy of tornado monitoring and early warning, this paper investigates the rare EF3-level tornado case that occurred on 19 September 2023 in Funing, Jiangsu, an unprecedented event for September in the history of Jiangsu. The analysis focuses on the reality and disaster situation, weather background and environmental conditions, and multi-band radar collaborative observations. The results are as follows. (1) The“9.19”Funing EF3-Level tornado was a strong tornadic event that occurred under the background of Meiyu weather. The air flow branching in the 200 hPa weather pattern and the wedge- shaped cloud in the 13.3 μm infrared satellite imagery were important indicators of deep convective forcing and advanced prediction of“9.19”Funing tornado. (2) Sudden changes of thermal and dynamic conditions signaled an extremely unstable atmosphere with strong vertical ascent, serving as important potential indicators for the triggering of a strong tornado. At 20:00 BJT on September 19 at the Sheyang sounding station, the Convective Available Potential Energy (CAPE) increased to 2 288.7 J · kg -1, Convective Inhibition (CIN) decreased to 0.2 J·kg -1, the Lifting Condensation Level (LCL) plummeted to 1 005.0 hPa (69 m), and K index increased to 40.2 ℃. Vertical wind shear rose to 10.9 m · s -1 (0-1 km), 19.2 m · s -1 (0-3 km), and 21.9 m · s -1 (0-6 km). (3) The multi-band weather radar network in northern Jiangsu can provide ultra-low altitude data, with the lowest detection height ranging from 100 m to 350 m, which greatly meets the internal needs of tornado monitoring and early warning. The multi-band weather radar in northern Jiangsu had a good adaptive scanning capabilities on the“9.19”Funing tornado. Without manual intervention, Baoying XD radar can carry out reasonable Range Height Indicator (RHI) adaptive scanning, completely capturing the evolution and vertical flow field of tornadic supercell. The Scans clearly revealed key structural featares: a low-to-mid-level reflectivity factor core (RC) and dome structure; middle-to-high-level overhanging echoes; a "V"-shaped gap at 3-5 km height; and a northeast-to-southwest oriented weak echo band between overhanging echoes of the dome and the middle-to-high-level overhanging echoes. The flow field was characterized by the vortex tube circulation in the forward-flank inflow, high-altitude subsidence flow, and the divided rear-flank inflow jet. These results provide a valuable reference for the multi-band weather radar monitoring and warning of tornadoes using multi-band weather radar in Jiangsu and contribute to the objective understanding of tornadic physical processes.