| 摘要: |
| 【目的】为了解2024年初长沙市3次低温雨雪冰冻天气过程差异。【方法】该文利用常规观测资料、地面自动站资料、ERA5再分析资料及风廓线雷达资料等多源资料，对1月21—22日暴雪（雨夹雪）过程及2月3—8日、2月21—25日低温雨雪冰冻灾害性天气过程进行综合分析，并总结降雪、冻雨发生条件。【结果】（1）3次过程在灾害类型、降水相态、降水强度、影响时间等方面存在较大差异。（2）1030 hPa线南压过长沙可作为长沙市低温雨雪天气发生条件之一。（3）融化层是决定降水相态转换（雨、雪、冻雨）的关键因子，冻雨的逆温层温差更大。长沙市降雪温度层结条件为：T₅₀₀≤−15 ℃、无融化层或融化层很浅薄（<0.1 km）、T₈₅₀≤−2 ℃、T地面≤0 ℃；冻雨温度层结条件为：−15 ℃1.2 km（或≥850 hPa）且融化层厚度>1.2 km。（4）风廓线雷达资料显示，降雪时段和雨夹雪时段冷暖气流交汇高度更高，3.5～4 km转西北风的时间可作为过程中降水停止的参考时间。【结论】雨夹雪下沉速度>降雪下沉速度；冻雨的下沉速度与降水量级有关：中雨量级的冻雨下沉速度>小雨量级的冻雨下沉速度。1月21—22日和2月3—8日过程大气湍流强，降水粒子对周围大气的拖拽作用更强。 |
| 关键词: 低温；暴雪；冻雨；风廓线雷达产品 |
| DOI： |
| 投稿时间：2024-04-30修订日期：2024-06-26 |
| 基金项目:湖南省自然科学基金项目(2025JJ80292); 长沙市自然科学基金项目(KQ2502335); 长沙市气象局科研项目(CSKY202406)。 |
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| Weather Analysis of Three Low-Temperature Freezing Rain/Heavy Snowfall Processes in Changsha in Early 2024 |
| yinlian,weiwenting,Shentianyao,Chenting |
| (Changsha Meteorological Bureau) |
| Abstract: |
| To understand the difference of the three low temperature freezing rain/heavy snowfall weather processes in Changsha City during early 2024, we comprehensively analyze the heavy snow (sleet) in January 21-22, low temperature freezing rain/heavy snowfall in February 3-8 and February 21-25 using conventional observation data, surface automatic station data, ERA5 reanalysis data and wind profiler radar data. Then, we summarize the occurrence conditions for snowfall and freezing rain. The results indicate that: (1) There are significant differences in disaster types, precipitation phases, precipitation intensities and influence time among the three processes. (2) The 1030 hPa line shifted southward and passed over Changsha, which can be considered as one of the indicators for the low temperature rain and snow weather in Changsha. (3) The melting layer plays a crucial role in determining the phase transition of precipitation (rain, snow and freezing rain), with larger temperature difference in the inversion layer of freezing rain. The temperature stratification conditions for snow and freezing rain in Changsha City areas as follows: snow: T500 ≤ -15℃, no melting layer or very shallow melting layer (<0.1 km), T850 ≤ -2℃, and Tground ≤0℃; freezing rain: -15℃ 1.2 km (or ≥850 hPa), and thickness of melting layer >1.2 km. (4) Wind profiler radar data suggest that during the periods of snowfall and sleet there is higher convergence height of cold and warm air. The time when wind turns northwest at an altitude range between 3.5-4.0 km can be used as reference time for precipitation to end during these processes. In conclusion, the sinking speed of sleet is larger than that of snowfall, the sinking speed of freezing rain is related to the precipitation magnitude, and the sinking speed of freezing rain in the scale of moderate rain is larger than the sinking speed of freezing rain in the scale of light rain. During the processes of January 21-22 and February 3-8, the atmospheric turbulence was strong, and the dragging effect of precipitation particles on the surrounding atmosphere was even stronger. |
| Key words: Low temperature; heavy snow; freezing rain; wind profile radar products |
