Land surface emissivity change in China from 2001 to 2010

Land surface emissivity is one of the important parameters in temperature inversion from thermal infrared remote sensing. Using MOD11C3 of Terra-MODIS L3 level products, spatio-temporal data sets of land surface emissivity in China for 10 years from 2001 to 2010 are obtained. The results show that the land surface emissivity in the northwest desert region is the lowest in China, with little seasonal variations. In contrast, there are significant seasonal variations in land surface emissivity in northeast China and northern Xinjiang, the Qinghai-Tibet Plateau, the Yangtze River Valley and the eastern and southern China. In winter, the land surface emissivity in the northeast China and northern Xinjiang is relatively high. The land surface emissivity of the Qinghai-Tibet Plateau region is maintained at low value from November to March, while it becomes higher in other months. The land surface emissivity of the Yangtze River Valley, eastern and southern China, and Sichuan Basin varies from July to October, and peaks in August. Land surface emissivity values could be divided into five levels low emissivity （0.6163-0.9638）, moderate-low emissivity （0.9639-0.9709）, moderate emissivity （0.9710-0.9724）, moderate-high emissivity （0.9725-0.9738）, and high emissivity （0.9739-0.9999）. The percentages of areas with low emissivity, moderate-low emissivity and moderate emissivity are, respectively, about 20%, 10% and 20%. The moderate-high emissivity region makes up 40%-50% of China＇s land surface area. The inter-annual variation of moderate-high emissivity region is also very clear, with two peaks （in spring and autumn） and two troughs （in summer and winter）. The inter-annual variation of the high emissivity region is very significant, with a peak in winter （10%）, while only 1% or 2% in other seasons. There is a clear association between the spatio-temporal distribution of China＇s land surface emissivity and temperature： the higher the emissivity, the lower the temperature, and vice versa. Emissivity is an inherent property of any object, but the precise value of its emissivity depends very much on its surrounding environmental factors.