一次冷空气大风水平与垂直风场结构分析

Structural Analysis of Horizontal and Vertical Wind Fields of a Cold Air Gale

利用MICAPS天气和区域自动站观测资料、美国NCEP 1°×1°再分析资料、上饶市TWP8-L对流层风廓线雷达资料,以及赣东北地形资料,采用天气学分析方法,对2017年11月17-18日江西出现的冷空气大风天气过程进行分析。结果表明:在极涡偏心型的环流背景下,冷空气势力强,自蒙古向东南方向经河套地区南下影响江西境内,影响期间中低层温度梯度大,达1℃/纬度或以上,地面变压梯度达9 hPa或以上。风廓线上高空风大,随时间推移往下渗透,冷空气过境时近地面风向有个转换过程,由偏西风转为偏东风。V-3θ图上,随着冷空气入侵,700 hPa以下θsed线与θ*线明显降低且位温向左突出,700 hPa以下向左突出越明显,斜率越大,底层风速越强。浙赣皖3省交界的地形使得冷空气偏北大风转为东北大风,冷空气在由东向西沿狭窄地形移动过程中,由于狭管效应,风速不断加大形成大风区。而狭窄地形又导致大风减弱消失的时间有4-5 h的延迟。对于预测上饶地区的冷空气大风提供了依据。

Using MICAPS weather and regional automatic station observation data,U.S.NCEP 1°×1°re-analysis data,Shangrao city TWP8-L tropospheric wind profile radar data,as well as the terrain data of north-east Jiangxi,the cold air gale weather appeared in Jiangxi on November 17-18,2017 was analyzed by means of synoptic analysis method.According to the results,the cold air is strong in the background of extreme vortex eccentric circulation.It affects Hetao area from Mongolia to southeast and then south to Jiangxi.The high-altitude wind on the wind profile is strong and penetrates down with the passage of time.When the cold air passes through,the wind direction near the ground has a conversion process,from the westerly wind to the easterly wind.V-3θfigure shows that with the invasion of cold air,theθsed line below 700 hPa and theθ*line obviously decrease and the position temperature protrudes to the left.The more obvious the position temperature is below 700 hPa to the left,the greater the slope is,and the stronger the bottom wind speed is.During the movement of cold air from east to west along the narrow terrain,due to the narrow pipe effect,the wind speed is increasing to form a strong wind zone.The loss of the gale was delayed by four to five hours.It provides a basis for predicting the cold air gale in Shangrao area.