Topography and Frontogenetical Process of Double Cold Front
地形与双冷锋的锋生过程

The frontogenetical process and development of a double cold front over a mountain are studied by using a semi-geostrophic model. The results show that the upper level part of the double cold front may be merged in the movement under the effect of deformation factor. In frontogenetical process, the intensity of the ahead front is strengthened much more than that of the back front in lower level. On the contrary, the back front is strengthened more than the ahead front in uPPer level. The influence of topography is importmant on the double cold front. Front movement is retarded and intensity is weakened on windward side of a mountain, and there is an accelaration of the front movement and an enhancement of the intensity on the lee side. Mountain has a promoting effect on the upper level part of double cold front, and causes the cold front to form a nose-shape lobe near the surface, topography increases greatly the vertical velocity in the front zone, and leads to a jump in vertical velocity. The impacts of mountains on fronts are limited within the lower troposphere.