Abstract: Based on the data from 15 meteorological stations covering the period from 1971 to 2015,this paper analyzed the spatio-temporal characteristics of snow cover days in Xilin Gol League,Inner Mongolia,China,by running t-test,Mann-Kendall test,wavelet analysis and empirical orthogonal function (EOF) method.The results are captured as follows:there was a sudden change in the snow cover days from many to less in 1996 and there was a quasi-periods of 7 years for this type of change.The monthly average of snow cover days showed a single peak type of distribution,with the months of December,January and February forming the peak which accounted for 69% of the total snow days while the sum of those in October and April taking up only 6%.The spatial distribution displayed a significant variation with larger numbers in the south and east and smaller numbers in the north and west in the region from an overall perspective.Except Erenhot and Sonid Right Banner,the snow cover days in most areas of Xilin Gol exceeded 90 days and therefore Xilin Gol is a region of stable snowing.The study region was divided into four categories based on the cluster analysis using the snow cover days and its influencing factors:the area with less snowfall but a big snow cover days,such as East Wuzhumuqinqi and Wulagai; the area where the snowfall is in accordance with the snow cover days and both are on the high side,such as Zhengxiangbai Banner and Taibus Banner; the area where the snowfall and snow cover days are in the median,such as Zhenglan Banner and Xianghuang Banner; the area where the snowfall is in accordance with the snow cover days and both are on the low side,such as Erenhot and Sonid Right Banner.From EOF method,there were three major spatial patterns in the region:(1) consistently more or fewer than the average in an area; (2) a seesaw between south and north; (3) a seesaw between central west and southeast.

Key words: snow cover days, spatiotemporal variation, Xilin Gol