混合层建立对一次强阵风天气过程的影响

摘要

Based on the NCEP reanalysis data and conventionally observational data,influence mechanism of estab-lishment of mixed layer (ML)on a strong gust weather process on March 23,2012 in Tianjin was diagnosed and simulated .The results show that joint action of strong pressure and allobaric gradient in front of cold high is synop-tic background of formation of surface strong gusts.Strong gusts occur in the period of higher surface temperature, lower pressure and low relative humidity.In the afternoon,the hot and dry convection within the deep ML makes the upper-level momentum that is in the north side of upper jet easily propagate to ground layer effectively,which leads to enhancement of surface gusts.The establishment of deep ML is another reason leading to formation of strong surface gusts.Results simulated by a WRF model suggest that local intensity of the ML may cause local differences of downward propagation of momentum,which may be the important factor causing spatial differences of gusts intensity over Tianjin.%利用NCEP再分析资料和常规地面观测资料，分析混合层的建立对2012年3月23日天津地区强阵风天气过程的影响机理。结果表明：强气压梯度和强变压梯度的共同动力作用是地面强阵风形成的背景条件。强阵风出现在午后气温较高、湿度较低且地面气压较低的时段。午后深厚混合层内的干热对流使高空急流北侧下沉气流将动量下传至对流层中层后向近地面层进一步有效下传，导致地面阵风增大。深厚混合层的建立也是地面强阵风形成的一个重要原因。WRF模拟结果表明，局地混合层强度差异使高空动量下传产生局地差异，可能是天津各地区阵风强度存在空间差异的重要原因。