Abstract

Water vapor is an important species in the earths atmosphere. It plays a major role in many atmospheric processes including weather, climate and atmospheric photochemistry. The distribution of water vapor in the atmosphere is highly variable and if we are to relate its variability to atmospheric effects, its spatial and temporal variability must be understood.

Remote measurements of water vapor distribution in the atmosphere frequently relies on differential absorption lidar (DIAL) techniques. These techniques require accurate spectroscopic data for the species of interest. These data include line position (wavelength) , absorption coefficients, pressure broadening parameters and pressure shift parameters. Temperature effects on these parameters is also important as it is more convenient to work with spectral lines which are relatively insensitive to temperature variations.

DIAL measurements must be made in a spectral region where the absorption cross sections have appropriate values for the density and measurement range of interest Optimum measurements are made in the range where the optical depth (one way) has a value near unity. To extend Dial measurements of water vapor into the stratosphere, where water vapor is less dense than in the troposphere, the water vapor band in the region of 940 nm is appropriate due to its stronger absorption.

© 1994 Optical Society of America