Abstract

Raman shifted laser-radar echoes from clouds are attenuated due to the cloud droplets’ extinction. However, multiple scattering effects in the presence of high optical-depth values in the cloud are adding to the expected signal from given altitudes. Such multiple scattering processes occur between any Raman molecular scattering (N₂, O₂ or any other gas with known spatial distribution) and any water droplet (or between a water droplet and a molecule) both contained within the field of view of the lidar system. In the case of double scattering, only two consecutive scatterings are taken into account, the first being within the transmitter field of view and the second within the receiving—system field of view. This case is valid for intermediate optical-depth values (0.1 to 0.4). The presence of a cloud acts as a "mirror" for the Raman scattering effect for all Raman scattering events occurring between the lidar and the cloud in both directions.