Versatile Lidar for Atmospheric Studies, Including Plume Dispersion, Clouds, and Stratospheric Aerosol

Abstract

A transportable scanning lidar for studying clouds, plume dispersion, and stratospheric aerosal at any of three wavelengths is described. A ruby laser transmits linearly polarized light of 694.3 nm wavelength at a maximum 0.8 s⁻¹ pulse rate. The lidar can discriminate between parallel, orthogonal, or combined polarizations of backscatter in a multichannel receiver. The lidar can simultaneously operate at the frequency-doubled wavelength of 347.2 nm. A frequency-doubled Nd:YAG laser, emitting at 532.0 nm and at a maximum pulse rate of 10 s⁻¹, normally Performs mapping of plume structure. Range resolution, including receiver response, is less than 7 m. The sample interval is typically 3 m for plume experiments and 15 m for stratospheric aeroso1 profiles. Beam divergence is less than 1.0 mrad, and the receivers field of view is adjustable up to 6 mrad. The lidar's sensitivity can be altered over a wide dynamic range by selection of optical filters in the receiver and adjustments in the photomultiplier voltage. Frequent calibration by backscatter from a diffusely reflecting target or from a haze-free region of the atmosphere is routine. Data acquisition and recording are controlled by computer.