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2024年2月我国两次大范围冻雨过程对比分析

Comparative analysis of two major widespread freezing rain events in China in February 2024

  • 摘要: 2024年2月1—4日(以下简称过程Ⅰ)及2月19—24日(以下简称过程Ⅱ),我国先后出现两次大范围雨雪冰冻过程,在这两次过程中冻雨影响范围广、持续时间长、灾害强度大,是我国有气象资料以来冻雨最为严重的一年。利用多源实况观测和ERA5再分析资料,对比分析了这两次冻雨过程发生的环境条件和温度层结特征。结果表明:(1) 两次过程中500 hPa环流形势和影响系统比较相似且均稳定维持,有利于大范围雨雪冰冻天气形势的持续,但低层温度配置和冷空气移动速度不同造成了冻雨落区存在差异。过程Ⅰ由于冷空气移速较慢,造成冻雨分布较为集中。相较于过程Ⅰ,过程Ⅱ初期西南急流强度更大、位置更北,导致冻雨初始发生位置偏北,但后期强冷空气迅速南下,造成冻雨落区移动速度更快,影响范围更大。(2) 两次过程中,中层暖层主要位于700—850 hPa之间,低层冷层则主要位于900 hPa以下,较通常冻雨概念模型中700 hPa暖层及850 hPa冷层位置偏低,易导致预报员对天气类型的误判,同时过程Ⅱ逆温层强度强于过程Ⅰ。(3) 采用面积元法分析了两次过程的中层暖层强度及低层冷层强度,结果表明过程Ⅰ冷暖层强度弱于过程Ⅱ,与温度特征分析结果一致。同时两次过程冻雨主要发生在中层暖层强度与低层冷层强度接近的地区。

     

    Abstract: Two large-scale snow and rain weather processes occurred in china from February 1-4, 2024 (Process 1, hereinafter), and February 19-24, 2024 (Process 2, hereinafter). During these two weather processes, the impact of freezing rain was extensive, the intensity of the disaster was severe, and the duration was long, which was rare in history. This study utilized multi-source observational data and ERA5 reanalysis data to focus on analyzing the environmental conditions and temperature layer characteristics of these two freezing rain events. The results indicate: (1) During both weather events, the 500 hPa weather patterns and influencing systems were quite similar, which were stably sustained, providing favorable conditions for widespread snow, rain, and freezing weather. However, there were differences in the low-level temperature configuration and the speed of movement. In Process 1, due to the slower movement of the cold air, the distribution of freezing rain was more concentrated. The initial southwest jet stream in Process 2 was stronger and positioned further north compared to Process 1, leading to the occurrence of freezing rain further northward. However, in the later stages, the rapid southward movement of strong cold air caused a fast-moving rain, snow, and ice, and thus a larger impacting range of the freezing rain. (2) In both processes, the mid-level warm layer was mainly located between 700 hPa and 850 hPa, while the low-level cold layer was mainly located below 900 hPa. The positions were lower than the classic conceptual model of a warm layer at 700 hPa and a cold layer at 850 hPa, which could easily lead to misjudgment of the weather situations and types. (3) Using the area method, the strength of the mid-level warm layer and the low-level cold layer was calculated separately for both processes. The results show that the strength of the warm and cold layers in Process 1 was weaker than in Process 2. In addition, the freezing rain in both processes mainly occurred in areas where the strength of the mid-level warm layer and the low-level cold layer were close.

     

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