2025年7月南疆盆地东部两次冰雹天气成因的对比分析

Comparative Analysis of the Causes of Two Hail Events in the Eastern Tarim Basin, Southern Xinjiang in July 2025

摘要: 基于多源气象观测资料、雷达图像产品及ERA5再分析数据，对2025年7月2日和7月4日发生在南疆盆地东部的两次冰雹事件进行了对比分析。结果表明，两次事件在环流背景、触发机制、风暴结构及雷达特征等方面存在显著差异。(1) 2025702个例主要受500 hPa槽底短波及低层切变线的影响，近地面存在明显的风场辐合区，对流风暴的组织性强，CAPE值高达1669.5 J∙kg⁻¹；而2025704个例则为槽后偏北气流引发的局地强对流，具有一定CAPE值，对流风暴发展主要受地形和水汽条件驱动，低层辐合线触发作用显著。(2) 通过对比物理量参数，两次个例的−20℃层高度均 < 7.2 km，−20℃层距0℃层高度差 ≤ 2.78 km，850 hPa与500 hPa温度差 ≥ 35℃，这些环境参量阈值可作为本研究区域冰雹判识的有效指标之一。(3) 雷达图像产品显示，2025702个例的雷达强回波中心在短时间内迅速增强(68 dBz)，冰雹指数(HI)指数显著，垂直积分液态水含量(VIL)的急剧跃增及衰减与冰雹的发生、发展过程高度相关。相比之下，2025704个例的VIL值变幅较小，回波强中心剖面表现为低质心降水特征，显示出强降水过程的持续性。本研究有助于深入理解南疆盆地东部冰雹的形成机制，并为提高该区域冰雹的监测预警能力提供了科学参考。

Abstract: Based on multi-source meteorological observation data, radar image products, and ERA5 reanalysis data, a comparative analysis was conducted on two hail events that occurred in the Eastern Tarim Basin, Xinjiang, on July 2 and July 4, 2025. The results show significant differences between the two events in terms of atmospheric circulation background, triggering mechanisms, storm structure, and radar characteristics. (1) The July 2nd event was primarily influenced by a 500 hPa trough-bottom shortwave and low-level shear lines, with a distinct surface wind convergence zone. The convection was well-organized with a high CAPE value of 1669.5 J∙kg⁻¹. In contrast, the July 4th event was triggered by post-trough northerly winds, with a moderate CAPE value. The convection development was mainly driven by topographic effects and moisture conditions, with significant low-level convergence playing a key triggering role. (2) A comparison of physical parameters showed that for both events, the −20˚C layer height was <7.2 km, the height difference between the −20˚C and 0˚C layers was ≤2.78 km, and the temperature difference between 850 hPa and 500 hPa was ≥35˚C. These environmental parameter thresholds can serve as effective indicators for identifying hail events in this study region. (3) Radar image products revealed that for the July 2nd event, the radar reflectivity center rapidly intensified (68 dBz) within a short period, with a significant hail index (HI), and a sharp increase and subsequent decay of the vertical integrated liquid water content (VIL), which was highly correlated with the occurrence and development of hail. In contrast, the VIL value for the July 4th event showed a smaller variation, and the reflectivity profile exhibited low-echo precipitation characteristics, indicating the persistence of the strong rainfall process.