The Relationship Between Snow Cover And Climate Change From 1996 To 2012 Across The Eurasian Continent

Eurasian continent is a main area of snow cover in the northern hemisphere,the maximum amounts of snow cover accounts for about 65% of the northern hemisphere.Under the influence of global warming,the snow cover propertities changed obviously.Meanwhile,snow cover itself is a product of the climate,and large-scale snow fluctuation are undoubtedly the result of air-sea anomalies.Climate warming usually leads to the shortening of the duration of seasonal snow cover in moutains areas and a significant reduction in snow cover area,causing a decrease in surface albedo,an increase in surface net radiation,thus resulting a remarkable positive feedback to climate system.In our research,snow depth data and meteorological elements covering from 1996-2012 from in-site stations were used to study spatial and temporal changes in snow depth,snow days,surface albedo,surface net radiation and temperature,investigate the relationships between snow cover and climate change,in addition,analyzing the intrinsic links between albedo and net radiation,and surface net radiation and temperature.The main conclusions are summarized as follows:1)The distribution of snow cover has a significant latitude zonality in Eurasian continent.The snow days and snow depth showed an unsignificant decreasing trend in 1996-2012.The snow days decreased significantly in October and increased in February.Snow depth decreased from October to May of next year,occurring a significant decrease in October and May when the largest reduction was at-2.0cm/10yr(p<0.05).Spatially,the significant decrease in snow cover located mostly north of 50°N,the significant increase distributed in the northeast of China,southern Xin Jiang and the vicinity of Baikal.The decreasing trend of snow cover showed in most of Siberia from October to December,the increase in snow days only showed in the southern of Central Siberia and northeastern China,however,the decrease in snow depth throughout the Eastern plains and Siberia from January to March,both of them decreased in the Siberia in April and May.2)The distribution of surface albedo has a regionality over Eurasian continent,the high values above 25% are mainly located in the southern of Central Siberai,Yakutia,northeast China and northern Xin Jiang,the low values below 10% are largely distributed in the Polar Circle,near the Caspian and in the Yangtze River basin.The albedo showed a decreasing trend in 1996-2012,especially in Winter,increasing trend in October and Spring,at a rate of 1.8%/10yr(p<0.05)in March.Spatially,the significant positive trends,more than 6%/10 yr,were observed in the southern of Siberia,northeast China and Xin Jiang,however,the negative trends mainly distributed in the Eastern Plains and the upper reaches of the Kolyma River basin at a rate of-6.5%/10 yr.3)The annual average surface net radiation at each station is greater than 0 KW/m2 in Eurasian continent,the high values about 21 KW/m2 located in Greater Caucasus,the southern of Central Siberia,the Yangtze River basin and the Tibetan Plateau,the low values below 12 KW/m2 distributed in nrorth of 60°N.The net radiation in the area covered by snow is less than 0 KW/m2 from October to February of next year,the minimum value appears in December.The change of surface net radiation showed an increasing trend in 1996-2012,especially in January at a rate of 0.2 KW·m-2·yr-1,showed an significant decreasing trend from February to May,particular in April at a rate of-0.2 KW·m-2·yr-1 ? Spatially,the decreasing trend distributed in Central Siberia,inner Mongolia Plateau,southern Xin Jiang and the QinghaiTibet Plateau,the increasing trend occurred in the Sakhalin,Eastern Europe plains,north of Xin Jiang and Yangtze river basin.4)The temperature decreased with increasing in latitude in Eurasia,which showed an increasing trend from 1996 to 2012,especially in October at a rate of 0.9?/yr,followed by in May,while which decreased in February at a rate of-1.5?/yr.Spatially,the significant warming occurred in the areas of high latitudes and elevations with a rate of above 0.1?/yr,however,the significant decreasing temperature trend distributed in the southern of Central Siberia and the eastern China.In autumn,warming shows in Siberia,in winter,the temperature declined in the southern of Siberia and China,rised still in most of areas of Eurasian Continent,in Spring,the significant increasing of temperature showed in north of 60°N at a rate of 0.31?/yr.5)The snow days and snow depth are positively correlated with surface albedo at a rate of 2.04%/day and 1.84%/cm,respectively.The most closely relationship occurs in April between snow days and surface albedo,and presents in October between snow depth and surface albedo,and the significant correlations are mainly distributed in the western Eastern Europe Plain and northern of China.There is a positive negatively correlation between snow cover and surface net radiation at a rate of-0.38 KW·m-2/day and-0.20 KW·m-2/cm,showing a most significant effect on radiation in April,and the significant correlations are found in the southern of Central Siberia.Also,there is a significant negative correlation between snow cover and temperature at a rate of-0.99?/day and-0.39?/cm,particular in October and November for snow days and snow depth and the correlations are mainly distributed in the western part of Eastern Europe and northeastern China.6)The surface albedo is significant negatively correlated with the net surface radiation at a rate of-0.27KW·m-2/%,especially in April at a rate of-0.34 KW·m-2/%,and the distribution of negative correlations in Central Siberia,Yakutia,Sakhalin,and the Tibetan Plateau,in winter and spring,the significant correlations occur in 45°N-60°N,northeastern China and the Loess Plateau,in Spring,which show in the polar and the Siberian Plateau.7)The net surface radiation significantly leads to increase in temperature at a rate of 1.55?/KW·m-2.The close relationship is obsevered from February to April,particular in April at a rate of 0.81?/KW·m-2,followed by in autumn.Spatially,occurring positive correlation in most of Russia,and negative correlation in China,in October and Spring,which shows a positive correlation betweem them in most of stations in Siberia,whereas in northern China,shows a obvious negative relationship for the period from November to February,the negative correlations dominated in Siberia,while in northeast China,Xin Jiang and Loess Plateau the positive correlations dominating.