复杂地形与锋面系统共同作用对台湾岛暴雨影响的数值分析

应用MM5V2数值模式输出的高分辨率资料对在复杂地形和锋面系统共同作用下台湾暴雨发生的水汽、垂直速度、低空急流等物理量场的中尺度特征进行了分析。表明地形是使锋面降水加强．最终形成暴雨的主要原因。在地形作用下，速度场、湿度场都具有比较稳定的局地特征，台湾岛迎风区保持着比背风区大的湿度场，流场表现为一个地形性中尺度环流。随着锋面系统的不断靠近，局地特征表现为加强和减弱两个阶段。发现迎风坡的低空急流主要是由地形引起的，它的南北向分布不均使空气发生了辐合上升运动，与地形和锋面引起的上升运动叠加，在地形迎风坡形成了一个垂直速度的大值区。有地形比无地形的降水明显加强。

THE EFFECTS OF FRONT AND TOPOGRAPHY ON HEAVY RAIN IN TAIWAN

In this paper the high resolution data created by numerical model MM5V2 was used to analyse the mesoscale features of relative humidity,vertical velocity and LLJ(low level jet)that induced by combining effect of front and complicated topography.It indicated that the topography was the most important factor of intensifying the rainfall and causing heavy rain at last.Velocity and relative humidity fields had relative stable local features under the effect of topography,relative humidity in windward side of topography had great value,but in the lee side of topography the humidity was low.It showed that there existed a topographical mesoscale circulation.The development of these fields was divided into two stages as intensifing and weakening with the nearness of front system.It also showed that LLJ was induced mainly by topography,the southern northern asymmetrical attribution of LLJ induced the convergence and uplift air,there came an area with high vertical velocity when uplift air induced by LLJ overlapped with the uplift air of front system.Rainfall was intensified when topography existed.