Evaluation and Cause Study on the Snow Disasters in Pastoral Areas of Northern Xinjiang

Past research has shown it is difficult to objectively assess the snow disaster of the actual situation on the basis of nature factor purely as to determine the snow disaster severity. We used the maximum snow depth,precipitation month by month,the temperature every day from 7 meteorological stations in Altay from 1961 to 2012,and precipitation from April to September,accumulated temperature greater than zero,the actual data of snow disaster situation over the same period,sunspot and herbage data from 2007 to 2012,studied the index and the causes of snow disaster in this area. The result showed that the comprehensive index of snow disaster has high accuracy for evaluating the snow disaster and the snow disaster could be divided into 4 classes: The most snow disaster years,secondary heavy snow disaster years,moderate snow disaster years and light snow disaster years. The most snow disaster years and secondary heavy snow disaster years mainly occurred in the early twenty-first Century,and the strength was more and more strong; The cause of the most snow disaster is the high frequency of heavy snowfall,and the strength is more and more strong; that of the most snow disaster years were mainly caused by the much more heavy snowfall frequency,the large amount of snow,stronger strength,long duration,but the cause of secondary heavy snow disaster years was more complex; sunspot activated low value years,Scandinavia positive phase circulation pattern,and the AO index was very weak,secondary heavy snow disaster occurred easily in Altay.