The Meinel band nightglow emission from the OH molecule has been used for decades to characterize mesospheric temperatures. Aeronomers currently rely on emission coefficients ("A coefficients") that the PIs argue are in need of revision. Temperatures recovered using the existing set of A coefficients differ by up to 15 K from actual temperatures computed from first principles. Large uncertainty in the mesospheric temperature can have detrimental effects on modeling chemistry, transport and circulation of the mesosphere and lower thermosphere (MLT). The uncertainties also undermine efforts to monitor the long-term temperatures in the MLT.
This proposal addresses the OH temperature determination by 1) using intensity-calibrated nightglow data that has been collected simultaneously over a large spectral range from astronomical sky spectra; 2) making comparisons between such recently obtained OH Meinel band line intensities, and the most recent first principles calculations of the emission coefficients. This research will contribute to understanding fundamental physical quantum processes, atmospheric motions on small and large scales, and long-term temperature change in the lower thermosphere.