Specific Features of Lidar Returns in Airborne Sensing of Seawater Containing Air Bubbles

Air bubbles arising in water under the action of wind-driven sea waves or as a result of the vital activity of a biomass and concentrated in the subsurface water layer change its optical properties. Their influence on the characteristics of a lidar return in seawater sensing with linearly polarized and unpolarized radiation is investigated. The dependence of the lidar return characteristics on the air bubble concentration and microstructure and of the optical and geometrical conditions of observations is examined for the radiation wavelength = 0.53 m.     

Polarization Structure of Multiply Scattered Background Components of Lidar Signals Reflected from Cloud Ice Crystals

A numerical experiment is performed to obtain the polarization characteristics of signals of a monostatic lidar intended for homogeneous cloud sensing. It is assumed that clouds consist of monodisperse randomly-oriented hexagonal ice crystals. To solve the vector radiative transfer equation, the light scattering phase matrices, preliminary calculated with the help of the beam splitting technique, are used as input data. The formation of the polarization structure of multiply scattered background signal component is studied for different scattering orders depending on crystal shapes and sizes and optical and geometrical conditions of the experiment.     

Average characteristics of laser radiation that has passed through broken clouds

Institute of the Optics of the Atmosphere, Siberian Branch, Academy of Sciences of the USSR. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radifizika, Vol. 32, No. 5, pp. 544–551, May, 1989.     

Reabsorption of laser-induced fluorescence in a plant canopy: Stochastic model

This paper continues the series of publications on the statistical simulation of transspectral processes. A system of interrelated radiative transfer equations is proposed. This system gives a formal basis for a numerical analysis of a wider range of spectroscopic effects that accompanies the propagation of laser radiation in the environment, such as the reabsorption of fluorescence in dense disperse media containing two and more fluorophores. As applied to the problem of lidar monitoring of the state of a plant canopy, an optical model is developed in which a leaf is not treated as an individual scattering element, but rather as a local volume of a multiphase medium with a complex polydisperse structure. The Monte Carlo algorithms have been modified so that they have achieved the simulation of fluorescence and reabsorption processes. Test calculations have demonstrated the adequacy of the proposed approach.     

Potential of pulsed excilamps for remote sounding of polluted atmosphere

The results are discussed of a closed numerical experiment on lidar sounding of the concentration of small gas impurities in the tropospheric layer of the atmosphere based on a new LIDAR-DOAS hybrid technology that uses a XeCl* excilamp as a source of pulsed broadband radiation. Quantitative estimates con-firm the promise of the approach, which expands the potential of the classical scheme of differential optical absorption spectroscopy (DOAS) with respect to the remote monitoring and localization of hazardous anthropogenic emissions of toxic gases. Combining the Monte Carlo method with the genetic algorithm for solving the inverse problem of reconstructing the profiles of sought gas constituents of the troposphere makes it possible to strictly quantitatively predict the efficiency of new promising lidar systems for monitoring the environment.     

Limits of applicability of the laser-location equation in the optical probing of clouds

By simultaneously solving the transient transport equation and the equation of laser location, the effect of the multiple-back-scattering background in a monostatic cloud-probing system on the accuracy of the optical measurement of back-scattering coefficients is analyzed. The transport equation is solved by the Monte Carlo method. Calculations are carried out for the most promising optical-probing wavelengths λ = 0.6943; 2.36 and 10.6μ, and a comparative analysis of their efficiencies is presented. The optical characteristics of a polydispersed liquid-drop cloud (one with a wide spread of particle sizes) are presented for the wavelengths in question.