Advantages of an Additional Raman Channel in Laser Sounding at Wavelengths of 355–1064 nm for Retrieving Microphysical Parameters of Atmospheric Aerosol

The potential and advantages of an additional Raman channel in the IR spectral region for the determination of microphysical parameters of aerosol are studied. Features of the joint retrieval of the complex refractive index m = m_real + i × m_image and the bimodal spherical particle size distribution function U(r) from lidar data are considered. A possibility of estimating m + U(r) is studied for weakly absorbing particles for m_image ≤ 0.010 when m^fine ≠ m^coarse. The algorithms are tested for one m^fine = 1.50 + i × 0.01 and nine m^coarse (m_real = 1.40, 1.50, and 1.60; m_image = 0.0001, 0.001, and 0.01). In order to take into account the influence of the contribution from the modal particles to the total concentration, 462 empirical models of U(r) are used.