Retrievals of Mesospheric Atomic Oxygen From SABER Measurements

Atomic oxygen is a highly variable component of the mesosphere which is of key importance in the chemistry and energetics of the region. The O concentration during both day and night can be derived by considering the ozone balance. During the daytime, production of ozone from O + O2 + M is balanced by its loss through photolysis. At night, the primary loss of ozone is through the H + O3 reaction. Measurements of the Meinel Band emission of excited hydroxyl radicals can be related to the H + O3 reaction rate, allowing a calculation of the O abundance (Good 1976, McDade and Llewellyn 1988). The Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) instrument aboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) spacecraft has been taking measurements of the O2(1Δ) emission at 1.27 μm (used to derive daytime ozone), OH Meinel Band emission at 1.6 and 2.0 μm, and other key parameters such as atmospheric density and temperature since early 2002. The TIMED orbit allows for the observation of all local times approximately once every sixty days. Atomic oxygen concentrations have been derived from the daytime SABER 1.27 μm ozone measurements based on the assumption of photochemical equilibrium (Mlynczak et al. 2007). We use the SABER observations of the Meinel Band emission to solve for the nighttime atomic oxygen profile. Preliminary values agree well with daytime results at high altitudes, where atomic oxygen is long lived, as well as with photochemical model results. We will present our retrieved atomic oxygen profiles and comparisons with atomic oxygen derived from measurements of O2(1Σ) by the TIMED Doppler Interferometer (TIDI), from measurements of O2(1Σ), O(1S), and OH(υ=9→4) by the High Resolution Doppler Imager (HRDI) aboard the Upper Atmospheric Research Satellite (UARS), and from measurements of OH(υ=8→3) by the Wind Imaging Interferometer (WINDII), also aboard UARS. The extensive spatial and temporal coverage of the SABER dataset will allow us to investigate the seasonal and solar cycle dependence of mesospheric atomic oxygen. <br /> <br /> REFERENCES:<br /> Good, R.E, Planet. Space Sci., 24, 389--395, (1976)<br /> McDade, I.C. and E.J. Llewellyn, Planet. Space Sci., 36, 897--905, (1988)<br /> Mlynczak, M.G. et al., J. Geophys. Res., 112, D15306, (2007)<br />