Research on Discrimination Criterion of Precipitation Types in Sichuan Province

The climatic distribution characteristics of different precipitation types in Sichuan province are analyzed using he meteorological data recorded reorganization from 1981~2013. And three different precipitation phases of different threshold ranges are summarized from surface and sounding factors. The main results are as follows:(1) The first eigenvector of rain days' EOF decreases gradually,the second eigenvector of rain days' EOF increases in Ya'an and Guangyuan areas,while the rain day's in Panzhihua also decreases. From the snow days perspective,the first eigenvector shows an decreasing trend of snow days in Sichuan. The second eigenvector shows that the snow days in the middle of Sichuan has slightly increased. The first eigenvector of rain and snow days reflects that the days of rain and snow in most of Sichuan areas are decreasing in recent 20 years,but the ones in Aba are increasing. It is not obvious that the second eigenvector shows. The third one tells us that the days of rain and snow in basin are increasing in recent 15 years,but the ones in west Sichuan plateau and pan-xi region are decreasing.(2) They are good indicators to distinguish different precipitation types,which are temperature and dew-point temperature in surface and sounding. T850hPa is something which distinguishes three different precipitation types in western Sichuan basin. All of the ingredients can distinguish the rain and snow in south Sichuan basin,but it is a difficult thing to make a distinction between snow and “rain and snow”. H700~first level is something which distinguishes three different precipitation types in northeast Sichuan basin. In west Sichuan plateau,H500~first level is good index to distinguish different precipitation types. In pan-xi region,the good indexes are temperature of first level,T600hPa,and the 0℃ level height.