| Snow is the main covering of the cryosphere,and glaciers and snow melt water is the main source of the world.Snow can affect the global climate system and the human living environment.With global warming and the sensitive response of snow cover to climate,snow has become one of the hottest topics in the world.As the main stable snow cover area of China,it has a developed animal husbandry,the water used by agriculture and animal husbandry and the construction of the area mainly comes from glaciers and snow melt in Altai region,Xinjiang;at the same time,the changes of snow cover can also affect the local tourism and traffic.The data used in this paper include optical remote sensing,passive microwave remote sensing and meteorological data and so on.The optical remote sensing data are mainly used for MOD10A2 to extract and analyze the areas and days of snow cover between 2001 and 2014 in Altai region,the passive microwave remote sensing data to extract and analyze the variation trend of snow depth between 2001 and 2014 in Altai region,and the meteorological data are used to study the relationship between the major snow cover parameters and climatic factors.This paper shows that:(1)The snow coverage ratio presented "Single Valley" trend within the year in Altai region,Xinjiang,there was a smallest proportion of snow cover area in July of the year,the lowest value was only 1.28%;the proportion in the three months of winter was more than 90%,the largest value was in January.The snow coverage ratio presented winter > spring > autumn > summer trend within the four seasons in Altai region,the winter as high as 48%,while the summer was only 3%,It has a large drop between summer and winter.During the study period,the proportion of the annual average snow cover was between 32.7% and 41.8%,the maximum value of snow cover ratio occurred in 2001,and the minimum value occurred in 2007,the snow cover ratio was fluctuating in the rest of the year;The spatial distribution characteristics of snow cover between 2001 and 2014 in Altai region were that it has a high snow cover ratio and snow frequency at high altitude and its surrounding areas,while the law is opposite in plain and low altitude areas.The distribution of stable snow in Altai region was relatively small,only 0.95%,and located in high altitude areas.(2)Depending on the division of annual average ratio of snow cover area by snow cover days between 2001 and 2014 in Altai region,the trend of change is as follows: middle days snow areas > long days snow areas > short days snow areas> perennially snow covered areas> unstable snow areas.The main form of snow in the Altai region were middle days snow areas,the annual average distribution area of 2001-2014 is 65.9% to the total area;and in the study period,the fluctuations were obvious,showing a downward trend,and the overall trend was downward;thoug the partition of snow cover days also fluctuated between years,the fluctuation smaller than middle days snow areas,and the variation of perennially snow covered areas and unstable snow areas were very weak.The snow covered days of Altai was uneven in spatial distribution,in the study area and time domain,the spatial transformation was more obvious between middle days snow areas and short days snow areas,and the interannual fluctuation was slightly significant.The snow covered days distributed along the Northwest-southeast direction,the areas of long snow cover days mainly distributed in the area with high altitude.(3)The average annual snow depth between 2001 and 2014 in Altai region was from 6.79 cm to 4.28 cm,and reached the maximum value of 6.79 cm in 2012,fell to the lowest value of 4.28 cm in 2014,the average value of snow cover was 5.32 cm during the study period,and the average annual snow depth fluctuated between years,it shows a downward trend.The monthly average value of snow depth in Altai region was unimodal,the monthly average snow depth reached the maximum value of 16.75 cm in February.The distribution of snow average depth was affected by altitude,temperature,precipitation and other factors,the distribution of snow depth in Altai region was related to the topography of the area,the average annual snow depth was affected by altitude,it reached the highest value of 9cm between 3200 and 3600 m In the study area and time.(4)The temporal and spatial variation of snow cover in the study area was also affected by climatic factors.the snow cover area ratio was negatively correlated to average temperature in all seasons except summer,also the average temperature and snow cover area ratio in spring have passed the 0.05 significant test,and presented a significant correlation.The precipitation was positively correlated to the snow cover area ratio in all seasons except winter,and the correlation were higher between spring and summer,especially significant in summer.The annual snow cover ratio was negatively correlated to average temperature,and the correlation coefficient was larger.The precipitation and the annual snow cover area ratio have passed the 0.05 significant test,and presented a significant correlation.Climatic factors had significant differences in covered area of different snow cover days,and there was a significant positive correlation between the average temperature and the snow cover in unstable snow cover areas and short days snow areas.Snow depth was related to meteorological factors,the precipitation and annual snow depth,average temperature and monthly snow depth all have passed the 0.05 significant test,and presented a significant correlation. |
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