Effect of Line-Width Data on Retrievals of Gas Concentrations in Limb-Viewing Experiments

Abstract

It has long been understood that accurate knowledge of collision-broadened halfwidths is necessary for infrared remote sensing of stratospheric minor gases. A careful examination of the curve of growth for typical stratospheric absorption lines indicates that for limb-viewing experiments, the long geometric paths through the atmosphere may result in higher sensitivity to collision broadening, relative to that of nadir-viewing experiments. Unfortunately, efforts in laboratory spectroscopy have usually been concentrated on obtaining line positions, strengths, and assignments, while the more difficult halfwidth measurements have been made very infrequently. In this paper, we present the results of halfwidth-sensitivity studies for ozone retrievals from typical limb-viewing absorption or emission experiments using both high-resolution spectroscopy and broad-band radiometric techniques.