Simultaneous Determination of the Aerosol Size Distribution, Refractive Index, and Surface Albedo from Radiance Data

In analyzing in detail the dependence of sky radiance on aerosol optical properties and surface albedo, we present a new method for the simultaneous determination of the aerosol size distribution, its wavelength-dependent refractive index, and surface albedo. The aerosol scattering phase function near 10°, its weighted phase function near 40° introduced in this paper, which can be inferred from sky radiance data, and the radiance near 90° are, respectively, used in retrieving the real and imaginary parts of the refractive index and surface albedo. Two main advantages to our method are: (1) the effect of the nonsphericity of particles on the refractive index solution can be expected to be less in view of using forward-semispherical scattering information; and (2) the retrieved imaginary part of the refractive index is insensitive to the real part, aerosol size distribution and surface albedo. The reasonableness and suitablity of the method ara tested in numerical experiments. Furthermore, this paper presents and analyzes the experimental results in simultaneous determinations of the atmospheric aerosol size distribution, refractive index, and surface albedo by use of the radiance data in almucantar measured by a radiometer.