Laser Radar Observations of Middle-Atmosphere Structure and Composition

A review is given of laser radar measurements of the atmosphere between about 5 and 100 km based on Rayleigh, Mie, Raman and resonance scattering processes, fluorescence and selective absorption. The results obtained with systems employing ultraviolet and visible wavelengths are examined in relation to the density and temperature structure at stratospheric and mesospheric heights, the changes in the stratospheric aerosol layer following the El Chichon eruption, the characteristics of particles in polar stratospheric clouds and of ice crystals in high-altitude cirrus clouds, and the height distributions of particular constituents. The use of infrared systems with coherent detection has, to date, been restricted to observations of Mie scattering from aerosols at heights up to the lower stratosphere. It seems likely that future developments will bring greater use of near- and middle-infrared wavelengths and probably space-borne laser radar systems.