Abstract: The surface humid index in Spring were calculated with the monthly precipitation and mean temperature and relative humidity data in spring from 1961 to 2008 of 12 meteorological stations in north Xinjiang.According to index,the inter-annual and interdecadal change characteristics of the surface humid index in spring and its distribution rule were analyzed.The results showed that the surface humid index in spring declines slowly since 1960s,its spatial distribution were meridional.The surface humid index in spring in the west area were greater than that of the east area in north Xinjiang,it showed that the spring drought in the east area were more serious than that of the west area in north Xinjiang.Meantime,the relationship between the surface humid index in spring and precipitation and temperature and air relative humidity were discussed and the spatial distribution of the frequency of the extreme dry/wet events in spring were analyzed in this paper.

Key words: Surface humid index, Variation characteristics, Frequency of the extreme dry/wet events, North Xinjiang