The relationship between surface spectral albedo and soil moisture in an arid Gobi area

Abstract

Surface albedo is one of the most important properties of underlying surface. However, errors still exist in the calculation of the surface albedo because of complex influencing factors. Understanding the relationship between the surface albedos in different wavebands, and soil moisture will provide theory basis for the parameterization of surface albedos. In this paper, using the data on the spectral radiation and soil moisture observation in Dunhuang, China, from August to October 2016, the spectral radiation characteristics of the underlying surface in this arid Gobi area, the variation characteristics of the surface spectral albedo and its relationship with 2-cm soil moisture were analyzed. The results show that the decrease of the angle of the sun due to seasonal change is the reason of the decrease of NIR, GR, VIS, and UV. The surface albedos in different wavebands are affected by the surface soil moisture, and they exhibit obvious anti-correlations. During the observation period, the average surface albedo of NIR, GR, VIS, and UV is 0.263, 0.230, 0.204, and 0.096, respectively, while the correlation coefficient with 2-cm soil moisture is − 0.522, − 0.678, − 0.804, and − 0.812, respectively. When solar altitude is larger than 40°, the correlation coefficients between the NIR, GR, VIS, and UV surface albedos and 2-cm soil moisture are becoming larger. And the linear regression coefficients between the NIR, GR, VIS, and UV surface albedos and 2-cm soil moisture are becoming smaller. Shorter wavelengths correspond to stronger relationships between the surface albedo and soil moisture. At longer wavelengths, the decrease in the surface albedo due to the increase in soil moisture is sharper.