地形影响下冷锋的变形及锢囚

DISTORTION AND OCCLUSION OF COLD FRONTS UNDER THE INFLUENCES OF OROGRAPHY

根据传统理论，将锋面看成密度的零级不连续面，设计了一个二层锋面模式，分别研究了东西走向与东北－西南走向的地形影响下冷锋的变形及锢囚现象。分析表明：不同高度的地形对于冷锋变形及锢囚的影响不同，同一高度的地形对于不同强度的冷锋运动也有不同的影响。通过分析研究，形象、直观地揭示了地形影响下冷锋变形及锢囚的一些规律，并与实际天气现象做了一些对比。此外，还分析了山区冷锋的垂直结构，指出冷锋在爬山时锋面中层会出现“隆起”现象，这反映了地形对于冷锋的非线性相互作用；锋面的这种“隆起”现象非常类似于气流过山时形成的“涌浪”（ｂｏｒｅ）。

ollowing classical theory, a two-layer frontal model is designed. It assumes that frontal surface is the zero-order discontinuty of density. In this paper, the model is used to study orographically distorted and occluded fronts. It is indicated that the distortion and occlusion of cold fronts are different under different conditions of orography. Frontal intensity has also influences on the distortion and occlusion. Some rules are revealed and compared with observations. In addition. we have analysed the vertical structure of cold front above mountain and found that frontal surface may be bulged under the influence of orography when it ohmes the mountain. The bulge of frontal surface is just like the bore which is pointed out by Long (1972) when he analysed fluid over obstacles.