2022年昌吉州一次特强寒潮过程诊断分析

Diagnostic Analysis of an Extremely Severe Cold Wave Process in Changji Prefecture in 2022

摘要: 本文利用常规实况观测资料和ERA5 0.25˚ × 0.25˚再分析资料，通过天气学原理和天气动力学诊断分析等方法对2022年11月26~29日昌吉州特强寒潮天气进行诊断分析。结果表明：此次寒潮天气具有历时长、范围广、降温幅度大、低温极端性显著、灾害性天气种类多等特点，出现在乌拉尔山高压脊发展后向东南衰退，引导西西伯利亚强冷空气南下东移的大尺度环流背景下；进入昌吉州的850 hPa冷空气中心达−32℃，冷高压沿西北路径侵入；强冷平流是造成本次寒潮剧烈降温的主要原因；强风的形成与冷平流和强烈的变压梯度有关。降水强盛时期，200 hPa天山南侧出现西风急流、300~500 hPa北疆西边境线风切变线(冷式风切变)、500 hPa槽前偏西气流转为西南急流、700 hPa中上游的塔城和克拉玛依站存在弱的风切变，加之有充分的水汽输送(中低层为水汽的辐合，高层为水汽的辐散)和动力条件(散度和垂直速度)，这种高低空的配置为此次寒潮天气提供了必要条件。

Abstract: In this paper, using the actual observation data and ERA5 0.25˚ × 0.25˚ reanalysis data, through methods such as synoptic principles and synoptic-dynamic diagnostic analysis, the extremely severe cold wave weather in Changji Prefecture from November 26 to 29, 2022 was diagnostically analyzed. The results show that this cold wave weather had the characteristics of a long duration, a wide range, a large temperature drop range, significant extreme low temperature, and multiple types of disastrous weather. It occurred under the large-scale circulation background where the high-pressure ridge over the Ural Mountains developed and then declined to the southeast, guiding the strong cold air from West Siberia to move southward and then eastward. The cold air center entering Changji Prefecture reached −32˚C at 850 hPa, and the cold high pressure invaded Changji Prefecture along the northwest path. The strong cold advection was the main reason for the sharp temperature drop during this cold wave. The formation of strong winds was related to cold advection and intense pressure change gradients. During the strong precipitation period, a westerly jet stream appeared on the south side of the Tianshan Mountains at 200 hPa, a wind shear line (cold wind shear) was present along the western border of northern Xinjiang at 300~500 hPa, the westerly air flow in front of the trough at 500 hPa turned into a southwest jet stream, and there was a weak wind shear at Tacheng and Karamay stations in the middle and upper reaches at 700 hPa. Coupled with sufficient water vapor transport (water vapor convergence in the middle and lower layers and water vapor divergence in the upper layer) and dynamic conditions (divergence and vertical velocity), the configuration in the upper and lower air provided the necessary conditions for this cold wave weather.