乌鲁木齐机场2021年“10.06~07”初雪天气过程及雨雪转化成因分析

Analysis on the Weather Process of First Snow and the Causes of Rain to Snow Transformation in Urumqi Airport during “10.06~07” in 2021

摘要: 本文利用FNL再分析数据、微波辐射计资料等对乌鲁木齐机场2021年10月6日~7日的初雪天气过程及复杂相态变化进行分析，结论如下：1) 巴尔喀什湖低涡系统是此次初雪天气的影响系统。前期低涡前部较强的偏西、西南急流为降水提供了较好的水汽输送，冷空气入侵造成的大尺度系统性抬升、低层较强的风速辐合及天山地形的强迫抬升为降水的持续和加强提供了有利条件，而低层温度迅速下降为雨雪相态转变提供了基本条件。2) 此次天气水汽输送和辐合主要在低层，前期低层显著的水汽输送，降水阶段明显的水汽辐合，整层长时间水汽饱和，均为降水加强、持续提供了有利的条件，而低层持续的上升运动为机场长时间的降水提供了较好的动力条件。3) 对机场产生复杂的雨雪相态变化分析发现，微波辐射计数据提供的高时间分辨率数据，为本次天气下复杂相态变化的分析提供了较好的数据基础。从温度演变来看，本次复杂相态变化可能是由于近地层水汽–雨–雪相态转变反馈导致。微波辐射计上温度在雨转雨夹雪时提前1~2小时的演变特征可作为雨雪相态转变临近预报的参考。

Abstract: In this paper, FNL reanalysis data and microwave radiometric data were used to analyze the weather process and complex phase changes of the first snow in Urumqi Airport from October 6 to 7, 2021. The following conclusions: 1) The low vortex system of Balkhash Lake was the influencing system of the first snow. The front of the early stage of the low vortex stronger by west, the south-west jet provides a better water vapor transmission, precipitation caused by cold air invasion of large-scale systemic lift and lower the stronger wind speed convergence and Mount Tianshan terrain forced uplift for the continuous and strengthening with the advantages of the precipitation, the temperature fell rapidly and the lower phase transformation provides the basic conditions for rain to snow. 2) The weather water vapor transport and convergence is mainly in the lower, the early stage of the lower significant water vapor transmission, precipitation phase clear water vapor convergence, the layer of water vapor saturation for a long time of precipitation strengthening continue to provide the favorable conditions, and low-level continuous upward movement to the airport for a long period of time precipitation provides better dynamic conditions. 3) The analysis of the complex phase changes of rain to snow in the airport shows that the high temporal resolution data provided by the microwave radiometer data for a better data basis on the analysis of the complex phase changes. From the perspective of temperature evolution, this complex phase change maybe caused by the feedback of water vaporrain-snow phase transition in ground layer. The evolution characteristics of temperature 1 to 2 hours in advance when rain turns to sleet on microwave radiometer can be used as a reference for the nowcasting forecast of rain to snow phase transition.