Specifics of laser sounding of atmosphere along horizontal and slightly slanting paths over water surface

The contribution of rereflection by a water surface to a lidar signal when making soundings along such paths are estimated. The case of atmospheric sounding along a horizontal path by a lidar situated at a stipulated height above the water surface is examined. The example given reveals the influence of rereflection on retrieval of the spatial structure of the backscattering coefficient beta for a monostatic lidar with stipulated characteristics. Undistorted profiles were obtained only for a height above sea level 10 m; in all other cases there was a considerable error. The lower the lidar was situated, the sooner did the zone of signal distortion appear. Appropriate expressions were derived which were experimentally checked in the Black Sea. Computations and in situ measurements revealed that the rereflection effect introduces a considerable contribution to the lidar signal and must therefore be taken into account in an investigation of atmospheric parameters. The influence of the described effects can be lessened by a decrease in the lidar angle of view and its placement at great heights.