Retrieval of kinetic temperature and carbon dioxide abundance from nonlocal thermodynamic equilibrium limb emission measurements made by the SABER experiment on the TIMED satellite

The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) experiment was launched onboard the TIMED satellite in December, 2001. SABER is designed to provide measurements of temperature, constituents, and the key radiative and chemical sources and sinks of energy in the mesosphere and lower thermosphere (MLT). SABER measures Earth limb emission in 10 broadband radiometer channels ranging from 1.27 μm to 17 μm. Measurements are made both day and night over the latitude range from 52°S to 83°N with alternating hemisphere coverage every 60 days. In this paper we concentrate on retrieved profiles of kinetic temperature (Tk) and CO2 volume mixing ratio (vmr), inferred from observed 15 μm and 4.3 μm limb emissions. SABER-measured limb radiances are in non-local thermodynamic equilibrium (non-LTE) in the MLT region. The complexity of non-LTE radiation transfer combined with the large volume of data measured by SABER requires new retrieval approaches and radiative transfer techniques to accurately and efficiently retrieve the data products. In this paper we present the salient features of the coupled non-LTE Tk/CO2 retrieval algorithm, along with preliminary results.