2018年10月乌鲁木齐暴雪过程锋面分析

Frontal Characteristics of the Snowstorm Process in Urumqi in October 2018

利用地面常规观测、NCEP/NCAR0.25°×0.25°再分析及风廓线雷达等资料诊断分析2018年10月17—18日乌鲁木齐极端暴雪天气过程的锋面特征。结果表明:在欧洲高压脊衰退,中亚长波槽分段东移的背景下,天山北坡强烈锋生并持续近30 h;此次锋生是热力和动力共同作用的,天山附近锋面呈带状准垂直分布,动力锋生激发的次级环流使垂直运动维持发展,为大暴雪提供动力条件;400~600 hPa西南和850 hPa至地面西北路径输送的水汽,在600~800 hPa强烈辐合,为乌鲁木齐暴雪提供充沛水汽。风廓线雷达监测资料中水平风向风速的垂直切变、C_n^2变化能够反映锋生和水汽的演变特征,也从观测事实上证实了锋面对动力抬升及水汽辐合的重要作用。

This investagation used conventional ground observation,the reanalysis data of NCEP/NCAR0.25°×0.25°and wind profile radar,the frontal characteristics of the extreme snow process in Urumqi on October 17-18,2018 were diagnosed and analyzed.The results show that under the background of the depression of European high ridge and the eastward movement of the long wave trough in Central Asia,the north slope of Tianshan Mountains was strongly frontogenetic and lasted for nearly 30 hours.This frontogenesis was generated by the combination of thermal and dynamic forced.The front near Tianshan Mountains was in a zonal quasi vertical distribution.The secondary circulation excited by dynamic frontogenesis keeped the vertical movement developing and provided the dynamic conditions for the blizzard.The water vapor between 400 hPa and 600 hPa transported by the southwest route and the northwest route of ground to 850 hPa,converged strongly between 800 hPa and 600 h Pa,where has abundant water vapor for the snowstorm in Urumqi.The vertical variation of wind speed in horizontal direction and the evolution characteristics of water vapor can be reflected by the wind profile radar monitoring data,and the important role of the front in dynamic uplift and water vapor convergence can also be confirmed by observation.