Simultaneous reconstruction of the complex refractive index and the particle size distribution function from the lidar data: examination of the algorithms
S.V. Samoilova
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
Keywords: аэрозоль, лидар, функция распределения частиц по размерам, комплексный показатель преломления, aerosol, lidar, particle size distribution function, complex refractive index
Abstract
A method is suggested for joint determination of two aerosol microphysical characteristics: the complex refractive index m = m real + i × m image and the spherical-particle size distribution function U(r) from the data of the nighttime vertical lidar sensing at the wavelengths 355-1064 nm. During their simultaneous estimation it is useful to minimize the discrepancy functional F(m) in the range of the physically justified m. The principal limitations due to a wider region of the global minima of F(m) appear at m trueimage Î [0.01; 0.04] and give rise to a potential shift of the resulting values of m estreal and m estimage. A simultaneous use of several functionals gives a better estimate of m due to different sets of the respective optical characteristics. The problem in retrieving the distribution function is caused by the information content of the coarse particle measurements. The statistical regularization method offers an unambiguous estimation of U(r) for the mean radius up to 3 mm, and gives an admissible estimate for larger radii. The algorithms have been tested using 8 values of absorption, when 50 empirical models of the size distribution function are assigned to one value m trueimage.
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