Laser scattering by spherical polydispersed aerosols as an inverse problem : numerical simulation and a mathematical model

Abstract EN

This work is concerned with the determination of the particle size distribution function n(r) for aerosois from measurements of the radiation intensity of scattered light.

A mathematical model is proposed to find the unknown function n(r) from a simulated data measurements of the differential volume angular scattering coefficient g (0, X) for various values of scattering function angles 0 = 0° (1°) 9° and ten lidar wavelengths A = 0.35, 0.55, 0.694, 1.06, 3.5, 4.0, 7.0, 9.1, 10.6, and11.0 um.

It is assumed here that the wavelength is comparable with particle size ranges; consequently, Mie theory is used.

This method, involve matching the optical data with the simulated data obtained from the direct solution ofthe ; problem.

For optimizing the solution, Hooke & Jeeves unconstrained إ optimization method is used to determine the coefficients of polynomial function of PSD that yield the best agreement with the measured optical data; where the objective function is the sum of the squared deviations.إ Different cases are presented for the inversion of three cloud models c.l,| C.2, and C.3.

The accuracy ofthe solution is depending on the observation scattering angle used, how many wavelengths used for detection, and the I degree of polynomial for the inverted PSD fonction.