Comparison of methods for determining concentrations of particles in a model scattering layer for an elastic scattering lidar

The topical problem of expanding the scope of application of elastic scattering lidars for determining the microstructure of the atmospheric surface layer containing polydisperse and nonspherical particles of various nature is considered. It is proposed to interpret the microstructure of the atmospheric layer as an equivalent scattering medium consisting of monodisperse particles. A comparative analysis of two methods for determining particle concentrations in the scattering surface layer of the atmosphere from lidar backscattering signals with simultaneous registration of the angular characteristics of the scattering halo of the probing beam and from the results of contact measurements using a nephelometer is carried out. Within the framework of the equivalent medium model, the microphysical interpretation of the backscattering and extinction coeffi cients measured by the lidar is considered. Within the framework of the equivalent medium model, the microphysical interpretation of the backscattering and extinction coeffi cients measured by the lidar is considered. Methods for determining the concentration of equivalent particles of a model scattering medium with a nephelometer by means of scattering on individual particles in the forward and backward directions are compared. The concentration of equivalent particles is determined from the results of relative measurements of the signals generated by the scattering of light radiation by individual particles, and it is shown that it is proportional to the ratio of the square of the unnormalized fi rst-order moment to the unnormalized second-order moment. It is noted that the unnormalized moments found from backscattering depend on the albedo of the particle, and the unnormalized moments found from forward scattering practically do not depend. It is noted that simultaneous measurements of signals generated by forward and backward scattering of radiation by individual particles make it possible to determine the relationship between the backscattering and extinction coeffi cients necessary for solving the lidar equation, and then use the backscattering coeffi cient to determine the concentrations of equivalent particles. The results of the performed analysis allow an unambiguous comparison of the concentration of equivalent particles with the measured backscatter signal. The results obtained can be applied in the development of remote methods for monitoring aerosol pollution of the surface layer of the atmosphere.

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