2020年3月18日中午至夜间,山西、河北、北京、天津和山东等地先后出现阵风10级及以上强风天气.利用风廓线雷达、国家级地面气象观测站和欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)第五代大气再分析数据(ECMWF Reanalysis v5,ERA5)等资料,对强风过程的天气学成因进行了分析.结果表明:强风发生在低空暖脊异常发展的热力环境条件下,冷锋自黄土高原下到华北平原,中层锋消,垂直方向上发生"断裂",低层冷锋先行侵入热低压,在锋生过程中发生.强风具有显著的非地转瞬变特征,低层强冷平流是强变压梯度产生的主要因素,变压风叠加在快速移动的冷锋系统中诱发大风,变压风是重要组成部分;低空动量下传效应引起低层风速波动,但不足以直接诱发强风.
Abstract
A cold-air windstorm processe(Beaufort wind force scale 10 or above)affects Shanxi,Hebei,Beijing,Tianjin,and Shandong successively from noon to night on 18 March 2020.The synoptic characteristics of the event are studied by using data of wind profile radars,national surface automatic weather stations,and ECMWF(European Centre for Medium-Range Weather Forecasts)Reanalysis v5(ERA5).The results show that the strong gale takes place in the abnormally developed thermal environment of low-level warm ridge when the cold front intrudes into the thermal low pressure with strong frontogenesis.The frontolysis occurs on the middle level when the cold front moves downward from the Loess Plateau to the North China Plain and shears off on the middle level.The strong wind has significantly ageostrophic character and transient variation.The low-level strong cold advection is the primary factor for severe allobaric gradient.The ageostrophic allobaric wind,which is superimposed on the fast moving cold front system,causes the highest wind speed,and the allobaric wind is the essential part of the strong wind.The lower-layer downward momentum effect induces the fluctuation of wind speed,but is not powerful enough to produce the strong wind directly.
关键词
春季冷空气/10级大风/锋生/变压风/动量下传/地转适应
Key words
spring cold air/windstorm/frontogenesis/allobaric wind/downward momentum effect/geostrophic adjustment
维普
万方数据