Scanning Raman lidar to measure atmospheric water vapor and aerosols

Raman lidar is an effective tool for measuring the vertical and temporal evolution of atmospheric water vapor and aerosols. The NASA/GSFC Scanning Raman Lidar (SRL) has participated in several coordinated field campaigns since its first operation in 1991. The measurement capabilities of the SRC are discussed and representative data are presented. This lidar is based on a XeF excimer laser with an output wavelength of 351 nm. The pulsed laser beam is directed into the atmosphere using laser-hardened dichroic mirrors. The signals backscattered from the atmosphere are gathered by a 0.76 m diameter telescope and detected using photomultiplier tubes. A photon counting data acquisition system operating at 100 MHz records the return signals. Four return signals are measured: the backscatter at the laser wavelength due to Rayleigh and Mie scattering from molecules and particles and the Raman shifted returns due to molecular water vapor, nitrogen and oxygen. The system includes a large 1.1 m×0.8 m scan mirror which allows the full aperture of the telescope to be scanned from horizon to horizon in a single scan plane