The Climatic Anomaly Characteristics Of Freezing Rain In Southwest China And Their Influence Factors

Change rules of meteorological elements in favor of Southwest China freezing rain have been analysed in the method of fuzzy information distribution by 96-station daily data range from 1961 to 2015. Evaluation standard is defined as. daily average temperature less than or equal to 2?, daily maximum temperature less than or equal to 8?,daily minimum temperature less than or equal to 0?, relative humidity more than or equal to 80%, and sunshine duration less than or equal to 2h. Based on the standard,number of freezing-rain days show a unimodal change between November to March and peaks in January. In addition, the index has been tested for reconstructing freezing rain intensity index to evaluate its spatial distribution in Southwest China.By analysing atmospheric general circulation of different intensity of freezing rain years, we found that during strong years, 500hPa geopotential height anomaly of Eurasia exhibit a dipole pattern with positive of north but negative of south, and vice versa. When it comes to temperature, inversion layer near the ground helps maintain the freezing rain during the intensified years. The analysis shows that the terrain also play an important role on freezing rain's formation. By adopting GIS model of precise distribution of meteorological elements in Southwest China, we found that the high altitude affect freezing rain hugely but relatively, Guizhou province is the most widely distributed area of freezing rain.North Atlantic SST, extreme cold events in China and the basic geographical elements of the Southwest are three main impact factors of freezing rain. Negative SST of North Atlantic is responsible for intensified freezing rain in the interannual timescale by the up and downstream effects which persist from autumn to winter, otherwise the freezing rain will get weak. Extreme cold events can also act as the predictors with an increased record of cold days and nights of next day. Calculation results show high climate disaster risk goes to most parts of northern Guizhou province. In general, GIS method of climate disasters reconstruction in Guizhou province behaves well among simulation results.