Abstract:

The analysis of the difference of forming environment of thunderstorm gales in different regions of Shaanxi Province is helpful to better understand thermal, dynamic and circulation characteristics of this kind of processes, and provide reference for the forecast and early warning of this kind of weather. Based on the surface observation data, lightning data and ERA5 reanalysis data of European Centre for Medium-Range Weather Forecasts from 2017 to 2022, the temporal and spatial distribution characteristics of thunderstorm gales in Shaanxi are analyzed, and the environmental parameters and circulation characteristics of warm type thunderstorm gales are compared and analyzed in different regions. The results show that northern Shaanxi and eastern Guanzhong are high-occurrence areas of thunderstorm gales, and warm type process is significantly more than cold type one. In summer this kind of weather process is much more than that in other seasons, and from June to August, the frequency of warm type processes in northern Shaanxi is significantly higher than that in Guanzhong and southern Shaanxi. The high occurrence period of thunderstorm gales is from 15:00 BT to 21:00 BT, and from 14:00 BT to 18:00 BT, the frequency of warm type processes in northern Shaanxi is significantly higher than that in Guanzhong and southern Shaanxi. There are some differences in thermal and dynamic conditions before the occurrence of warm type thunderstorm gales in different regions. Before the occurrence of warm type processes in northern Shaanxi, the energy and water vapor conditions are relatively weak, while the dynamic condition is relatively strong. But in southern Shaanxi, the energy and water vapor conditions are relatively strong, and the dynamic condition is relatively weak. The circulation types with frequency higher than 15% are northern Shaanxi west wind type and anticyclone with west wind type, Guanzhong west wind type and anticyclone with west wind type, southern Shaanxi cyclone with west wind type and anticyclone with west wind type. For the northern Shaanxi west wind type and anticyclone with west wind type, northern Shaanxi is located at the bottom of cold vortex or low trough, or between the bottom of low trough and the subtropical high, and the temperature difference between 850 and 500 hPa is larger, which provides certain unstable conditions for the occurrence of convective weathers. There is shear near the average occurrence position of warm type thunderstorm gales, which is conducive to the triggering of convective weather. For the west wind type in Guanzhong, the southerly airflow in the lower layer is stronger, and the dew point depression is smaller. For the cyclone with west wind type in southern Shaanxi, the T-ln P diagram shows a near-V shape and the energy condition is better. For the anticyclone with west wind type in Guanzhong and southern Shaanxi, the T-ln P diagram shows a near-V shape and the water vapor conditions are better.

Key words: thunderstorm gales, environmental parameters, circulation characteristics, Shaanxi

摘要：

分析陕西不同区域雷暴大风形成环境差异，有助于更好地掌握此类过程的热力、动力和环流特征，为该类天气的预报预警提供参考。基于2017—2022年地面观测资料、闪电资料和欧洲中期天气预报中心（European Centre for Medium-Range Weather Forecasts，ECMWF）发布的第五代全球气候再分析资料（ERA5），分析陕西雷暴大风时空分布特征，并分区域对比分析暖型雷暴大风的环境参数和环流特征。结果表明：陕北和关中东部为雷暴大风高发区，暖型雷暴大风明显多于冷型；夏季远多于其他季节，6—8月暖型雷暴大风陕北明显多于关中和陕南。雷暴大风高发时段为15：00—21：00（北京时，下同），且14：00—18：00暖型雷暴大风发生频率陕北明显高于关中和陕南。不同区域暖型雷暴大风发生前热力、动力条件存在一定差异，陕北过程前能量和水汽条件相对较弱，动力条件相对较强；陕南能量和水汽条件相对更强，动力条件相对较弱。频率高于15%的环流型为陕北西风型和反气旋配合西风型、关中西风型和反气旋配合西风型、陕南气旋配合西风型和反气旋配合西风型。陕北西风型和反气旋配合西风型，陕北位于冷涡低槽底部或低槽底部与副热带高压之间，850 hPa和500 hPa温差较大，为对流天气发生提供了一定的不稳定条件，过程平均发生位置附近有切变存在，有利于对流天气触发；关中西风型，低层偏南气流较强，温度露点差较小；陕南气旋配合西风型，T-ln P图表现为近V型且能量条件较好；关中和陕南反气旋配合西风型，T-ln P图表现为近V型且水汽条件较好。

关键词: 雷暴大风, 环境参数, 环流特征, 陕西