Iterative method for the inversion of multiwavelength lidar signals to determine aerosol size distribution

Two iterative methods of inverting lidar backscatter signals to determine altitude profiles of aerosol extinction and altitude-resolved aerosol size distribution (ASD) are presented. The first method is for inverting two-wavelength lidar signals in which the shape of the ASD is assumed to be of power-law type, and the second method is for inverting multiwavelength lidar signals without assuming any a priori analytical form of ASD. An arbitrary value of the aerosol extinction-to-backscatter ratio (S-1) is assumed initially to invert the lidar signals, and the ASD determined by use of the spectral dependence of the retrieved aerosol extinction coefficients is used to improve the value of S-1 iteratively. The methods are tested for different forms of altitude-dependent ASD's by use of simulated lidar backscatter-signal profiles. The effect of random noise on the lidar backscatter signals is also studied. (C) 1998 Optical Society of America.