Numeric Simulation of Influence of the Topography on Continuous Freezing Disaster Distribution Occurred South of China at Beginning of 2008
地形对2008年初中国南方持续性冰冻灾害分布影响的数值模拟

The early year of 2008,a large-scale and sustained low-temperature,freezing rain and snow weather occurred in South of China. The disaster caused by freezing rain and snowstorm was unprecedented,and break 50-year records in many areas. In this paper,mainly,the most severe stages from 25 January to 2 February 2008 are discussed. After successfully simulating the precipitation the surface temperature and vertical distribution of temperature field i.e. reproduction the peculiar severe events by CWRF numeric model,a topographic sensitive test showed,the topography have vital influence on the formation and maintenance of freezing rain,which result from the changes of front characteristics. The inclined backwards front zone will be generated easily because the warm and wet air elevations and cold air accumulation in near surface layer when topography exist. But the slope grade of front will increase and the inversion layer structure which support the freezing will be destroyed without topography,so freezing(frozen) disaster areas will weaken quickly and disappear after short-term expansion into west and south. In addition,the removing of above mountains will change the features of circulation and the easterly airstream in low troposphere will be more organized,the return-flow will also be more clear. These changes have a significant impact on the intensity and region of heavy precipitation in South of China,but have no obvious effects on general precipitation distribution.