Abstract
Thermal infrared emissivity of sand, sampled in the Muus Desert in China, have been measured under controlled soil moisture content in order to obtain quantitative relationship between soil moisture arid spectral emissivity. Spectral emissivity of the dried sand, which contains large amounts of quartz and feldspar, shows a depression in the 8-10μm range. However, the emissivity increases in the 8-10μm range when there is an increase in the soil moisture content, and no changes are observed in the 11-13μm range. In some cases, however, this phenomenon is not clear because of temperature estimation error in the sample.
An error of 1°K in temperature estimate causes about a 2% emissivity error and less than 0.5% error in the emissivity ratio in the thermal infrared. The emissivity ratio of averaged ASTER TIR channels (10, 11, 12):(13, 14) is proposed to be an indicator of the soil moisture content. This ratio increases by about 3% with increase in moisture content from 0 to 2% in weight.
