邵阳地区2024年三次低温雨雪冰冻过程分析

Analysis of Three Cryogenic Freezing Rain and Snow Weather Processes in Shaoyang Area in 2024

摘要: 利用常规观测资料和ERA5再分析资料，分析了2024年1~2月影响邵阳地区的3次低温雨雪冰冻天气过程的特征及成因差异。结果表明：(1) 3次过程500 hPa均受“两槽一脊”环流和偏强西太平洋副高影响。过程I乌拉尔山以北阻塞形势有利于冷空气快速南下，冷空气强度强，降雪量大且短暂；过程II和过程III冷空气分股东移南下，强度偏弱，降水相态复杂且历时长。(2) 3次过程中低层均伴有较强偏南风发展，过程I冷暖气流在邵阳地区交汇最剧烈；过程I和II中700 hPa邵阳上空存在较强水汽辐合，与雨雪的量级和强度有较好对应。(3) 700 hPa、850 hPa 0℃线，925 hPa −4℃线以及地面0℃线，可作为雨转雪相态变化的参考值。当中低层存在显著暖性逆温，地面 ≤ −1℃，可作为雨转冻雨的参考值。双偏振雷达产品在本次过程中对降水相态的演变及判定有较好的指示作用。

Abstract: Based on conventional observation data and ERA5 reanalysis data, three cryogenic freezing rain and snow weather processes that affected the Shaoyang region from January to February 2024 were analysised. The results showed that: (1) three processes were influenced by the “two troughs and one ridge” circulation and the stronger western Pacific subtropical high at 500 hPa. In Process I, the blocking situation in the northern Ural Mountains facilitated the rapid southward movement of cold air, resulting in intense cold air, heavy but brief snowfall. In Processes II and III, the cold air masses split and moved eastward and southward with weaker intensity, complex precipitation phases, and a longer duration. (2) During three events, there was a development of strong southerly winds in the middle and lower layers, the convergence of cold and warm air currents was most intense in Shaoyang area during Process I. Strong water vapor convergence was observed over Shaoyang at 700 hPa in Processes I and II, which correlated well with the magnitude and intensity of precipitation. (3) The 0˚C isotherms at 700 hPa and 850 hPa, the −4˚C isotherm at 925 hPa, and the ground-level 0˚C isotherm can serve as reference points for the phase change from rain to snow. When there is a significant warm inversion in the middle and lower layers and the ground temperature is ≤−1˚C, these conditions can serve as a reference for the transition from rain to freezing rain. The dual-polarization radar product provided valuable indications for the evolution and determination of precipitation phase states during these events.