Information properties of fluctuating components of lidar signals in sounding the upper ocean through a rough sea

The problem of lidar remote sensing of the upper ocean through a rough water-air interface is considered. The depth-dependent variance of backscattered signal fluctuations caused by surface roughness is investigated. In regions of the most characteristic depths, simple approximating formulas are proposed for some parameters of the depth-dependent variance such as the depth of maximum fluctuations, the magnitude of maximum fluctuations, and the rate of fluctuation attenuation for depths where the fluctuation variance decays exponentially. These formulas make it possible to determine the volume scattering coefficient of water and the wind velocity near the water surface from measured values of the above parameters. An expression for the fourth moment of the fluctuations of the backscattered signal power is derived and its dependence on the basic parameters-the depth of sounding, the wind velocity near the water surface, the velocity of the lidar over the surface, and the sample length (spatial scale of averaging)-is calculated. It is shown that the sample of a length of about 100 m is sufficient to estimate the fluctuation variance with reasonable accuracy throughout nearly the entire variation range of significant parameters of the problem.