Properties of atmospheric aerosol extinction for the satellite radiometric calibration site of Dunhuang, China

Atmospheric spectral extinction measurements for the Gobi Desert were performed with a spectroradiometer and a Halon standard reference during June 1994 at the Gobi of Dunhuang, China. Optical thickness and the size distribution of aerosol particles were retrieved from results of the measurements and some related data. The comparison between the results of the measurements and those measured at some eastern parts of China shows that the aerosol model of the site was similar to the rural ones of these eastern parts of China, and also indicates that there is a certain proportion of large particulates (r⩾1.0 μm) in the atmosphere of this site. A comprehensive sensitivity study has also been made using numerical simulation methods to determine the effects of the variations of imaginary parts of the complex refractive index and particulate size on aerosol extinction for visible (0.55 μm) and thermal IR (10.6 μm) wavelengths. In general, aerosol absorption is linear with the imaginary part of refractive index for relatively large particles (for example, r=2.0 μm given in the paper). For the range of particle radii (0.01 μm⩽r⩽10.0 μm) given in this article, aerosol absorption is stronger dependent on the geometric radius of aerosol particulate for the visible wavelengths, and aerosol scattering is almost linear with it for the range 0.01 μm⩽r⩽0.2 μm of radii in the same wavelengths