Errors in Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) kinetic temperature caused by non-local-thermodynamic-equilibrium model parameters

The vast set of near-global and continuous atmospheric measurements made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument since 2002, including daytime and nighttime kinetic temperature (T<inf>k</inf>) from 20 to 105 km, is available to the scientific community. The temperature is retrieved from SABER measurements of the atmospheric 15 μ CO<inf>2</inf> limb emission. This emission separates from local thermodynamic equilibrium (LTE) conditions in the rarefied mesosphere and thermosphere, making it necessary to consider the CO<inf>2</inf> vibrational state non-LTE populations in the retrieval algorithm above 70 km. Those populations depend on kinetic parameters describing the rate at which energy exchange between atmospheric molecules take place, but some of these collisional rates are not well known. We consider current uncertainties in the rates of quenching of CO<inf>2</inf>(v2) by N<inf>2</inf>, O<inf>2</inf> and O, and the CO<inf>2</inf>(v<inf>2</inf>) vibrational-vibrational exchange to estimate their impact on SABER T<inf>k</inf> for different atmospheric conditions. The T<inf>k</inf> is more sensitive to the uncertainty in the latter two, and their effects depend on altitude. The T<inf>k</inf> combined systematic error due to non-LTE kinetic parameters does not exceed ±1.5 K below 95 km and ±4-5 K at 100 km for most latitudes and seasons (except for polar summer) if the T<inf>k</inf> profile does not have pronounced vertical structure. The error is ±3 K at 80 km, ±6 K at 84 km and ±18 K at 100 km under the less favorable polar summer conditions. For strong temperature inversion layers, the errors reach ±3 K at 82 km and ±8 K at 90 km. This particularly affects tide amplitude estimates, with errors of up to ±3 K. Copyright 2008 by the American Geophysical Union.