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At present the economic feasibility and effectiveness of airborne systems of oceanological and ecological studies is quite obvious. The information about the state of a medium is retrieved from the shape of lidar return signal. Interpretation of results is quite a difficult problem by itself, because sea water is a multicomponent medium. The distortion of a signal shape occurs due to multiple interaction of radiation with scattering and absorbing particles. Moreover, the pulse shape can be additionally modified due to atmospheric scattering and interaction with the air—— water interface when using airborne sounding systems. Nonstationary interface under the effect of wind—driven sea waves results in intensification of reflection and rereflection of radiation scattered by the atmosphere. Low optical density of atmospheric layer tends to accumulate large mean free paths of photons, i.e., signals from water P(t) and from the atmosphere and air——water interface Pa(t) enter a detector simultaneously. In Refs. 1—3 it was pointed out that the atmosphere influences shaping of lidar return signal coming from a subsurface water layer. A delayed decay of the lidar return signal P(t) starting from a certain depth was experimentally observed in Ref. 1. Levin and Feigels3 explained this effect by the contribution of the signalP(t), moreover, they proposed an approximate analytical expression for estimating Pa(t). In the design and performance of lidar measurements account must be taken of the above—indicated effect; in this connection it is necessary to study it in more detail. We think that the statistical simulation should be performed for determining the role of different factors in shaping of the signal Pa(t) as well as for estimating the optical conditions and viewing geometry under which the atmospheric signal may limit the depth of sea water sensing. The most complete data on the atmospheric component of lidar return can be obtained from the solution of the radiative transfer equation with the given boundary conditions. Such a solution was found by the Monte Carlo method.
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