乌鲁木齐机场两次强降雪过程对比分析

Comparative Analysis of 2 Snowstorms at Urumqi Airport

本文选取乌鲁木齐机场2021年年初和年末两次强降雪天气过程,利用常规地面、高空形势场资料、FNL再分析数据对两场降雪的天气配置、水汽输送路径、动力条件进行诊断分析。结果表明:1) 中空和高空强盛持久的西南急流为暴雪提供了有利的水汽输送,中低空明显的风向切变、风速辐合为引起上升运动起到了有效作用,但降雪发生前“11·26”过程在新疆西部国境线的西南急流轴明显短于“1·23”过程。2) 两次天气过程均存在低空风与地形结合的强迫抬升运动,但“11·26”过程的强迫抬升运动明显弱于“1·23”过程。3) “1·23”过程的垂直上升运动的厚度显著大于“11·26”过程,“1·23”过程的强降雪发生时段与上升运动最强的时段相吻合,但“11·26”过程的强降雪时段与上升运动的高度和厚度增加相对应。两场降雪过程的垂直上升运动的减弱时间与降雪减弱的时间一致。

In this paper, selecting 2 snowstorms weather processes at Urumqi Airport at the beginning and end of 2021. The weather configuration, water vapor transport path and dynamic conditions of the 2 snowstorms are diagnosed and analyzed by using conventional ground and upper air situation field data and FNL reanalysis data. The results show: 1) the strong and persistent Southwest jet in the middle and upper levels provides favorable water vapor transport for the blizzard, and the obvious wind shear and wind speed convergence in the middle and low levels play an effective role in causing the upward movement. However, the Southwest jet axis in western Xinjiang during the “Nov. 26” process before the snowstorm is significantly shorter than that during the “Jan. 23” process. 2) There is forced uplift in a combination of low-level wind and terrain in both weather processes, but the forced uplift in the process of “Nov. 26” is significantly weaker than that in the process of “Jan. 23”. 3) The thickness of the vertical ascending motion in the process of “Jan. 23” is significantly greater than that in the process of “Nov. 26”. The period of snowstorm in the process of “Jan. 23” is consistent with the period of the strongest ascending motion, but the period of snowstorm in the process of “Nov. 26” corresponds to the increase of the height and thickness of the ascending motion. The weakening time of vertical upward motion of the 2 snowfall processes coincides with the weakening time of snowfall.