2008年1月10日—2月2日我国中南部地区发生了严重的低温雨雪冰冻灾害。该文分析此次过程的冷空气活动和水汽输送，比较两者在降水形成中的相对重要性。利用文中定义的两个参量，可以直接比较水汽和温度这两个量在降水中所起的作用，并比较两者作用的相对重要性。结果表明：在低层（850 hPa 及以下），我国中南部地区温度偏低、水汽偏少，但温度偏低对降水偏多的正贡献大于水汽偏少的负贡献，两者的净贡献为正，因此，冷空气活动主导降水。在较高层（600 hPa 及以上），中南部地区水汽偏多、温度偏高，但水汽偏多对降水的正贡献大于温度偏高的负贡献，因此，水汽输送主导降水。在中层（700 hPa），干冷空气和暖湿空气混合导致，中南部地区水汽偏多、温度偏低，两者均有利于空气饱和，对降水均起正作用；计算结果显示，水汽的贡献略强于温度的贡献。%The severe cryogenic freezing rain and snow disastrous weather occurrs in central-southern China from 10 Jan to 2 Feb in 2008,which lasts for nearly a month,causes huge social and economic impacts.The wa-ter vapor supply and the cold air surges of this disaster are investigated,and their effects on the formation of the heavy snowstorm are performed.The abnormality of the atmospheric circulation is that the blocking high remains stable in high latitudes of the Northern Hemisphere,the western Pacific subtropical high is more north than normal and the south branch trough is active.In this process,cold air continuously trans-ports from north to central-southern China,forming a high isentropic potential vorticity center.At the same time,there is also strong water vapor continuously transports to north,the integrated water vapor is more than normal in the central-southern China,but at 850 hPa and levels below,the moisture is less.At different levels,anomalous temperature and moisture are different.From low layer to high layer,the air temperature change from abnormally low to abnormally high.The moisture increases and turns into more than normal at 700 hPa.Some methods are defined to examine whether moisture and temperature both play positive roles in this event.Results indicate that at 850 hPa and levels below,although warm and moist air transport from the south,dry and cold air transport from the north is very strong,so the abnormally low air temperature caused by the cold air surges dominates the abnormally high relative humility,and the pre-cipitation is more than normal,resulting in less moisture is less than normal,but this negative effect is weaker than the positive effect of abnormally lower air temperature.On the contrary,at 600 hPa and lev-els above,although the dry cold air transport from north,the warm and wet air from south is very strong, the abnormally more water vapor dominates the heavy precipitation,the air temperature is warmer than normal,and it has a negative effect at 700 hPa,the result of the blend of the warm and moist air from the south with the dry and cold air from the north is that the air over the central-southern China is moister while colder than normal.They both have positive contributions to the heavy snowstorm.It shows from calculation that at this level,the moistness of the air contributes more than the coldness of the air.
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