中低纬度系统相互作用过程的中尺度风场分析OA北大核心CSTPCD

Based on the observation data from two dual S-band Doppler radars in Jinan and Binzhou,this paper uses the method of direct synthesis to retrieve a 3-dimensional mesoscale wind field for an extreme precipitation caused by the convergence between Typhoon Lekima and a westerly trough.The results are shown as follows.(1)The long-term maintenance of a shear generated by the convergence of cold and warm airflows in the interaction between the westerly trough and the typhoon is the key to the extreme precipitation.The warm airflow advances first and then retreats,a southeast and a northwest airflow cross the radar station successively,and within a small time frame a composite shear occurs vertically.(2)Maximum updraft occurs in the windward area of convective cells with the largest gradient of reflectivity,and maximum downdraft appears downwind the echo top.It is a weak wind area near the echo center at the mid-and low-levels;(3)There are cyclonic inflows at all layers of developing convective cells and anti-cyclonic outflows at the upper layer of mature convective cells.(4)Vertical wind shears are a main factor affecting the increase of precipitation in rain clusters,and mature rain clusters are so structured that their convective cells are low-centroid,and vertical motion is the strongest.