Study On Climatic Background Concerning Icing And Assessment Of Risk Intensity In Southwest China

The configuration of main meteorological element based on Fuzzy information distribution method of probability by using daily meteorological elements data for the period of 1960-2009 from 96 stations in Southwest China, to the number of icing consecutive days mainly constructing icing comprehensive evaluation index.The database of geographical factors as longitude, latitude,slope,aspect and sky-view factors by using digital elevation model (DEM) and GIS are obtained.Based on the mathematical theorem of tendency simulation and stepwise regression, the GRID of icing meteorological element and icing comprehensive evaluation index are established.Based on the index,the region of Southwest China is zoned for 3 ranks of icing intensity.When the conditions that daily maximum temperature in the context of-10℃and 1℃,relative humidity greater than or equal 80%, sunshine duration less than or equal 2 satisfy at the same time, the probability of formation ice will increase. Snowy mountains region which lies to the western margin of the Sichuan Basin whose elevation is about 3500 m is easy to achieve the formation of ice temperature. The conditions of relative humidity and sunshine duration are easy to achieve both at the south margin of the Sichuan Basin and the junction of Guizhou,Sichuan and Yunnan province. These three conditions which are low temperature,high humidity and scant sunlight, acting in concert with each other, are easy to form ice. The mountains region to the basin west of in the West is zoned as light ice area.Junction of Southern Gansu and Yunnan in the west are at the middle rank.The regions of Yunnan, Guizhou, Sichuan border, and south of Daba Mountains are always the heavy ice area. There is obvious interdecadal variability in annual icing intensity in Southwest China, decadal variability in heavy ice area is very prominent especially. In the global context of climate warming, the trend of series of cumulative days of icing conditions is going up significantly.For diverse terrain in southwest China, topography have a greater impact in all ice weather conditions.The icing conditions and the mean icing intensity (risk) models all pass the test. Generally, the affect of macro-topographic factors is greater. The accuracy of relative humidity model is improved by micro-topographic factors.The models of icing conditions shows that the macro-topographic have great impact on the conditions, especially the elevation. The maps of icing intensity (risk) model in Southwest China Can reaction the distribution of ice risk, especial in Guizhou,match well with the actual situation.