THE THEORETIC STUDY ON THE RETRIEVAL OF AEROSOLS’ VOLUME DISTRIBUTION FROM SOLAR SPECTRAL REFLECTANCE

The outgoing solar radiation at the top of the atmosphere can be solved by the basic radiation theory. At the same time, the spheric particles' scattering can be solved by Mie theory. With these two solutions, the kernel function to retrieve atmospheric aerosols'volume distribution(integrated over the vertical column of atmosphere) was derived from the solar spectral reflectance in this paper. The kernel function here was affected by two factors:scattering angle and wavelength. And its weighting properties decide whether the particle size can be retrieved successfully from solar spectral reflectance. After analyzing the characteristics of kernel function, a quite simple linear inversion scheme was designed. With it,two sets of trials were performed to retrieve the aerosols' volume distribution. In the trials,the solar spectral reflectance at the top of the atmosphere was simulated by a pre-built radiation transfer model. One trial is designed to test the effect of different aerosol loading on retrieval scheme and the other is to test the effect of different aerosol complex refractive index. Both of trials show that the retrieved volume distributions keep good coincidence with the given one. These results prove that aerosols' volume distribution can be inferred from the solar spectral reflectance. By introducing the concept of kernel function, the aerosol size inversion can be explained with explicit physical basis. In addition, the inversion processing here just depends on a few parameters calculated from Mie theory. Compared with the look-up table method, which is used frequently and widely in the present,the database to retrieve aerosols' size distribution was simplified greatly.