Ozone Corrections for Rayleigh-Scatter Temperature Determinations in the Middle Atmosphere

Abstract

A well-established technique for the determination of temperature in the middle atmosphere is the retrieval of temperature profiles from density profiles of air. The measurement of air density profiles from the ground and from space are typically determined from measurements of Rayleigh-scattered light. Most researchers using the Rayleigh-scatter temperature technique do not state whether they correct their measurements for the absorption of light due to ozone in the upper stratosphere. Such corrections may have been less significant for initial studies of temperature, but with the current need for temperature measurements of sufficient quality to access atmospheric change, these corrections take on an added importance. Significant improvement to the temperature measurements in the stratosphere are shown to result by including this effect for any reasonable choice of ozone profile. Simple correction functions are presented for temperature measurements, appropriate for low, middle, and high latitudes evaluated at two of the three most common Rayleigh-scatter wavelengths, 532 and 589 nm. Though the 350-nm wavelength is also commonly used for Rayleigh-scatter measurements, the effects of ozone at this wavelength are found to be negligible. The correction functions increase the temperature in the middle stratosphere by about as much as 4 K, with the largest corrections at the low latitudes and the longer wavelength, 589 nm. Deviations from these baseline values due to seasonal variability in the ozone profile change the temperature correction by less than 10%. Despite increases of two to three times of ozone in the mesosphere during the spring season, mesospheric temperatures are found to not require any correction for ozone. Hence, even without explicit knowledge of the ozone profile, experimenters can still significantly improve their Rayleigh-scatter stratospheric temperature measurements compared to not correcting for ozone absorption.