Spatial And Temporal Variations Of Glacier Surface Temperature And Albedo In The Qinghai-Tibetan Plateau During The Past 20 Years Using MODIS Data

Under the background of global warming,varying degrees of retreat has occurred in the glaciers on the Qinghai–Tibetan Plateau in China,the ice and snow-albedo feedback mechanisms is considered to be one of the main reasons for the accelerated retreat of glaciers.Glacier surface temperature is a direct reflection of the heat budget and melt extent of the glacier surface.Glacier albedo is a key parameter to control the energy budget process on the surface.These two parameters are of great significance to establish the glacier energymass balance model and understand the response of glaciers to climate change.Therefore,it is necessary to carry out the research on the characteristics of the spatiotemporal changes and influencing factors of the surface temperature and albedo of the glaciers on the Qinghai–Tibetan Plateau,so as to provide a scientific basis for the research on glacier changes and material balance of the glaciers on the Qinghai–Tibetan Plateau.Recently,satellite remote sensing data has the characteristics of easy access,long time and wide range,which has been widely used in the study of spatiotemporal changes in glacial surface temperature and albedo.The surface temperature data from MOD11A1 and the albedo from MOD10A1 were taken as the main data source of the study.Based on the data about surface temperature and albedo extracted from the Second Glacier Inventory Dataset of China,the surface temperature and albedo data of the glaciers on the Qinghai–Tibetan Plateau from 2001 to 2018 were collected to analyze the spatiotemporal distribution characteristics of year,season and month from pixel scale and watershed scale.Followed by the analysis of the relationship between the surface temperature and albedo as well as mass balance.Finally,the effects of snow particle size,light-absorbing impurities and cloud on the surface temperature and albedo of the glaciers were discussed in this study.The main results and conclusions are as follows:(1)The inter-annual changes in the surface temperature of the glaciers on the Qinghai–Tibetan Plateau showed an overall rising trend from 2001 to 2018,with rate of 0.41?/10 a,2002 was the year with the lowest surface temperature and 2017 was the year with the highest surface temperature.The albedo of the glaciers on Qinghai–Tibetan Plateau showed a decreasing trend from 2001 to 2018,with rate of-0.012/10 a.The surface temperature and albedo of the glaciers on the Qinghai–Tibetan Plateau showed a negative correlation.The inter-annual correlation coefficient was-0.62(p<0.05)from 2001 to 2018,the correlation coefficient in the spring was-0.82(p<0.05),that in the summer was-0.79(p<0.05),autumn was-0.85(p<0.05)and winter was-0.27.(2)There was a clear difference in the spatial distribution for the surface temperature and inter-annual albedo of the glaciers on the Qinghai–Tibetan Plateau based on the pixel scale.The temperature increase rate of the glaciers in the southern plateau was higher than that of the northern glaciers,meanwhile the albedo decrease rate of the glaciers in the southern plateau was lower than those in the northern part.The surface temperature and albedo of the glaciers were differently distributed in different seasons,in which the spatial differences of glaciers surface temperature were the most obvious in winter and spring.The changes in surface temperature and albedo of the glaciers on the northern and southern parts of the plateau were different every month.(3)The spatiotemporal characteristics of surface temperature and albedo were analyzed after selecting 10 typical glaciers.The average value and inter-annual changes in surface temperature and albedo of these typical glaciers in different types and regions had obviously different spatial distribution characteristics.The albedo of polar continental glacier on northern plateau was relatively high,the inter-annual decrease rate of the albedo was relatively small,the surface temperature of these glaciers was lower than the oceanic glaciers on the southern area,and the surface temperature of certain glaciers was decreasing.The albedo of the oceanic glaciers in the southeastern Qinghai–Tibetan Plateau was low,and the inter-annual decrease rate was relatively high,meanwhile,the surface temperature of most glaciers was relatively high,and the rate of temperature rising was much higher than northern glaciers.(4)The Qinghai–Tibetan Plateau was divided into 11 areas based on the watershed scale before calculating the inter-annual and seasonal rate of changes in surface temperature and albedo of the glaciers in each area.There was a certain correlation between the rate of changes in glacier albedo and the glacier mass balance.The area with a high rate of decrease in glacier albedo generally had a serious loss of mass balance,such as the Yarlung Zangbo River Basin and Salween River Basin in south eastern Qinghai–Tibetan Plateau.(5)According to different types of glaciers,the rate of changes in surface temperature and albedo of the glaciers on the Qinghai–Tibetan Plateau to altitude were counted.The surface temperature of oceanic glaciers,sub-continental glaciers,and polar-continental glaciers at an elevation of 4000-7000 m mainly showed a rising trend,while the albedo showed a decreasing trend.Winter was not only the season when the rising rate of surface temperature remained high,but also the season when the albedo decreases the most.