2024年2月黄石市两次低温雨雪冰冻过程对比分析

Comparative Analysis of Two Low-Temperature Rain-Snow and Freezing Weather Processes in Huangshi City in February 2024

摘要: 本文利用常规观测资料、雷达、ERA5再分析资料等对2024年2月黄石市两次低温雨雪冰冻过程进行分析，得到以下结论：(1) 两次过程均持续时间长、影响范围广，雨雪相态复杂。第一次雨雪量更大，主要以雨为主；第二次降温幅度更大，以冻雨、冰粒、雨夹雪、雪为主。(2) 两次过程均发生在高空槽东移与低层冷空气共同作用的环流背景下，暖湿气流在冷垫上爬升，低空急流提供充沛的水汽条件，也使得中层逆温层和融化层建立并维持，导致降水相态复杂。(3) 两次过程均存在逆温区，但第二次逆温范围较第一次过程更广，冷空气也更强，冷垫更深厚，冷中心温度更低，融化层高度更高，持续时间更长，因此冻雨特征更明显，固态降水以冰粒为主。(4) 数值模式对于第一次过程的强降水落区及强度把握较好，第二次过程对风场预报存在偏差，低层切变线位置预报偏南，移动偏快，中层风向辐合预报偏弱，导致模式降水预报的量级较实况明显偏小。

Abstract: This paper analyzes two low-temperature, rain-snow and freezing weather events in Huangshi City in February 2024 by using conventional observation data, radar and ERA5 reanalysis data. The main conclusions are summarized as follows: (1) Both events were characterized by long duration, wide influence range and complex precipitation phases. The first event had larger precipitation amount and was dominated by rainfall; the second one witnessed a greater temperature drop, with dominant precipitation types including freezing rain, ice pellets, sleet and snow. (2) Both processes occurred under the circulation background of the eastward movement of the upper trough combined with low-level cold air. The warm and moist airflows climbed over the cold wedge. The low-level jet provided abundant water vapor conditions, facilitating the formation and maintenance of the mid-level inversion layer and melting layer, and consequently resulting in complicated precipitation phases. (3) Inversion layers existed in both events. Compared with the first process, the second one featured a wider inversion coverage, stronger cold air, a deeper cold wedge, lower temperature in the cold core, a higher melting layer and longer duration. Therefore, it presented more significant freezing rain features, with ice pellets as the major solid precipitation. (4) Numerical weather models performed well in predicting the falling area and intensity of heavy precipitation for the first event. However, obvious biases existed in the wind field forecast of the second event: the forecasted low-level shear line was located further south and moved faster, and the forecasted wind convergence in the middle level was weaker, which led to a significant underestimation of precipitation magnitude compared with the actual observation.