云南大理州一次风雹天气过程诊断分析

Diagnostic Analysis of a Hail Weather Process in Dali Prefecture of Yunnan Province

摘要: 本文以2025年8月5日大理州一次典型风雹天气过程为例，综合利用地面常规观测资料、探空资料及再分析数据，对其环流背景、相关诊断量特征及中尺度触发机制等诊断分析，结果表明：500 hPa环流场中，高纬度低涡引导冷空气南下，中低纬度副热带高压边缘引导暖湿气流北上，二者在大理附近交汇，同时风场辐合促使暖湿空气强烈上升，构建了有利的大尺度环流背景。动力条件上，天气过程期间，禾甸镇中高层存在显著上升运动，为强对流提供关键动力，下沉运动与之配合形成强烈垂直气流切变，且风场有效输送暖湿气流和不稳定能量，成为强对流发生的直接动力因素。热力条件方面，禾甸镇假相当位温垂直分布的不均匀性是不稳定能量积累的重要基础；西南地区K指数空间差异显示云南西部及部分中部大气不稳定度高、对流潜力大；温度平流变化，尤其是中层冷平流侵入，加大大气垂直温度梯度，进一步增强大气不稳定度，提供了充足热力条件。此外，丽江探空站资料表明，强天气发生前大气已处于不稳定状态，具备强对流所需的充足不稳定能量(较高CAPE值)及有利动力抬升条件(低CIN、负SI、利于边界层空气抬升的BLI)，为灾害发生提供了必要局地条件。

Abstract: In this paper, a typical wind hail weather process in Dali Prefecture on August 5, 2025 is taken as an example. Based on the conventional ground observation data, sounding data and reanalysis data, the circulation background, related diagnostic characteristics and mesoscale triggering mechanism are analyzed. The results show that in the 500 hPa circulation field, the high-latitude vortex leads the cold air to the south, and the edge of the subtropical high in the middle and low latitudes leads the warm and humid air to the north. The two converge near Dali, and the wind field convergence promotes the warm and humid air to rise strongly, which constructs a favorable large-scale circulation background. In terms of dynamic conditions, during the weather process, there was a significant upward movement in the middle and upper layers of Hedian Town, which provided the key power for the strong convection. The sinking movement cooperated with it to form a strong vertical airflow shear, and the wind field effectively transported warm and humid airflow and unstable energy, which became the direct driving factor for the occurrence of strong convection. In terms of thermal conditions, the inhomogeneity of the vertical distribution of pseudo-equivalent potential temperature in Hedian Town is an important basis for the accumulation of unstable energy. The spatial difference of K index in Southwest China shows that the atmospheric instability is high and the convective potential is large in western and central Yunnan. The change of temperature advection, especially the intrusion of cold advection in the middle layer, increases the vertical temperature gradient of the atmosphere, further enhances the atmospheric instability, and provides sufficient thermal conditions. In addition, the data of Lijiang sounding station show that the atmosphere was in an unstable state before the occurrence of strong weather, with sufficient unstable energy (higher CAPE value) and favorable dynamic uplift conditions (low CIN, negative SI, BLI conducive to boundary layer air uplift) required for strong convection, which provided the necessary local conditions for the occurrence of disasters.