Doppler detection of hydroxyl column abundance in the middle atmosphere

The hydroxyl column abundance in the middle atmosphere is measured with ground-based uv spectroscopy using the sun as a light source. The present method is distinctive in that it utilizes the Doppler shift of the solar spectrum due to the solar rotation to discriminate the slight terrestrial hydroxyl absorption from prominent solar features. By comparing the spectra measured on the east and the west edges of the solar disk, it is possible to cancel out most of the solar structures and to make the terrestrial features much more evident.