|其他摘要||Snow is one of essential factors in cryosphereand snow is very sensitive to climat change and meantime snow can affect hydrological cycle system According to the fifth assessment report of IPCC, global warming of the climate system is unequivocal, which reconfirmed that the fact of the world is warming. Under the background, the present study extrated snow-cover data using ERA-Interim and verified the results’ accuracy by MODIS snow products. Then, we calculated the annual snow initial date and ending date from 1987 to 2014 and obtained snow distribution patterns. The characteristics of snow temperal changes in Central Asia were inveatigated by calculating the changes within year and changes in inter-annual. The characteristics of snow spatial changes were analyzed using EOF and R/S methods and then the development trends of snow changes were estimated. Finally, the changes in past 30 years of the North Pacific Oscillation and Central Asian climates variables, such as air-temperature, precipitation, sea level atmospheric pressure, wind speed and so on, were investigated. The key climate factors that affected the snow changes in Central Asia were investigated using partial correlation method. The main contents and conclusions are as follows:
(1) Snow cover data was calculated from ERA-Interim data, and the results were validated using measured snow depth data and MODIS snow product. The results showed that the accuracy of snow depth data extracted from ERA-Interim is about 72.1% compared to measured data, and the average absolute error of snow cover is 3.32% with RMSE of 0.042 compared to the results of MODIS snow product. The results can satisfy snow change analysis. (2) Accumulation of snow in Central Asia started in early October, reaching to the maximum in January and February, and the minimum in October and April. The fluctuations of minimum snow cover data are less than these of the maximum. Both maximum and minimum had a tendency of decreasing according to regression analysis, but not significant.
(3) In the past 30 years, the initial dates and the ending dates of snowing in high latitude areas and surround mountain areas have the tendency of delaying one month and advancing one month, respectively. Snow cover durations are always short in low latitude areas, and snow cover began to disappear in the some regions of Uzbekistan and Turkmenistan, extending from southeast of Central Asia to northeast.
(4) Snow cover had great differences in spatial distributions, with the maximum appeared in mountains and plateaus and followed by the north of Kazakhstan. Except for mountain areasand plateaus snowing frequency is strongly correlated with latitude, Studying the spatial variation of snow distribution on the day of severe cold, the results showed that the area of snow cover in Central Asia is decreasing with the significance at the level of 0.05. This phenomenon started in 2005 and became remarkable in 2009.
(5) The key anomaly changes of snow cover was mainly distributed in the Kunlun mountains, the southern slope of Tianshan mountain, and followed by southwest region of Kazakhstan. Using Empirical Orthogonal Function (EOF) method and Mann-Kendall methods to validate snow cover changes in Central Asia in the past 30 years, the results showed that snow cover had mutated from 2000 to 2005. The most significant changes were happened in mountain areas, plateau and Kazakhstan. The second mode of EOF showed that the change of low and high altitude was inverted. The future variation of snow cover duration in Central Asia was predicted by rescaled range analysis.
(6) Through the partial correlation analysis, the order of influence power of climate factors that impacting snow cover was temperature, wind speed, precipitation and sea level pressure in descending order. In terms of spatial distribution of snow, the key factor in the high latitude was wind speed. The influence of temperature was greatest and occupied 62.9% areas in the entire Central Asia. Overall, the main driving forces in low altitude areas, high latitude areas and high altitude areas were temperature, wind speed and precipitation respectively.|