天津地区一次冷锋后大风过程特征及成因分析

Characteristics and Causes Analysis of a Gale Process after Cold Front in Tianjin Area

利用常规地面气象观测资料和FNL逐6 h全球再分析资料,对2018年2月10日—11日天津地区冷锋后大风天气过程特征进行分析,探讨此次陆地大风天气过程的成因。结果表明:后倾的天气形势与强大少动的地面冷高压共同作用形成的强气压梯度为此次大风的产生提供了根本动力;大风期间建立了自上而下的冷空气传输通道,高层深厚的冷平流传送到中低层促使地面风速增大;200 hPa高空入口区辐合下沉运动造成动量下传是大风维持的重要原因;风速波动与地面变压和冷平流的时空演变、锋生作用有较好的对应,风速峰值在变压梯度峰值后6~12 h出现,而且越靠近6 h正变压中心、500 hPa和700 hPa冷平流中心,其强度、梯度越强,地面风速也越大。

Based on conventional surface meteorological observation and FNL 6 hourly 1°×1° global reanalysis data,the characteristics and causes of a gale process happening after cold front in Tianjin area from February 10 to 11,2018 were analyzed. The results showed that the barometric gradient formed by the combined action of the backward weather situation and the strong and less moving ground cold high pressure provided the fundamental power for the gale. During the gale period,a top-down cold air transmission channel was established,and the deep cold advection in the upper level was sent to the middle and lower level to promote the increase of ground wind speed. The downward transmission of momentum caused by the convergence and subsidence in the 200 hPa high-altitude entrance area was an important reason for gale maintenance.The wind speed fluctuation had a good correspondence with the spatio-temporal evolution of surface allobaric gradient and cold advection and frontogenesis. The peak value of wind speed occurred 6 to 12 h after the peak value of allobaric gradient.The closer to the center of positive allobar for 6 h and the center of cold advection for 500 hPa and 700 hPa,the stronger the center intensity and gradient were,the higher the surface wind speed was.