Observation of Raman scattering by cloud droplets in the atmosphere

In a recent field campaign, the NASA Goddard Space Flight Center scanning Raman lidar measured, in the water vapor channel, Raman scattering from low-level clouds well in excess of 100% relative humidity. The excess scattering has been interpreted to be spontaneous Raman scattering by liquid water in the cloud droplets. A review of research on Raman scattering by microspheres indicates that the technique may provide a remote method to observe cloud liquid water. The clouds studied appear, from Mie scattering, to have two distinct layers with only the upper layer showing significant Raman scattering from liquid water in the droplets.