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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2016-766
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
22 Nov 2016
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Resolving the mesospheric nighttime 4.3 μm emission puzzle: New model calculations improve agreement with SABER observations
Peter A. Panka1,2, Alexander A. Kutepov2,3, Konstantinos S. Kalogerakis4, Diego Janches2, James M. Russell5, Ladislav Rezac6, Artem G. Feofilov7, Martin G. Mlynczak8, and Erdal Yiğit1 1Department of Physics and Astronomy, George Mason University, Fairfax, Virginia, USA
2NASA Goddard Space Flight Center, Greenbelt, MD, USA
3The Catholic University of America, Washington, DC, USA
4Center for Geospace Studies, SRI International, Menlo Park, California, USA
5Center for Atmospheric Sciences, Hampton University, Hampton, VA, USA
6Max Planck Institute for Solar System Research, Göttingen, Germany
7Laboratoire de Météorilogie Dynamique/IPSL/FX-Conseil, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91128 Palaiseau, France
8NASA Langley Research Center, Hampton, Virginia, USA
Abstract. Since 2002, SABER (Sounding of the Atmosphere using Broadband Emission Radiometry)/TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics) has been continuously measuring the day- and nighttime infrared limb radiances of the mesosphere and lower thermoshere (MLT) in ten broadband channels. Recently, the MLT daytime temperature/ pressure and CO2 densities have been obtained self-consistently from SABER 15 μm and 4.3 μm emission observations. However, similar nighttime data remain unprocessed due to a lack of understanding of the 4.3 μm emission generating mechanisms. A previous study suggested the “direct” transfer OH(v)) ⇒ N2(v)) ⇒ CO2(v3)) ⇒ 4.3 μm of vibrational excitation from OH(v) to CO2 in the nighttime mesosphere. However, accounting for this excitation mechanism alone leads to significant under-prediction (by up to 80 %) of observed 4.3 μm limb radiances. Recently, theoretical and laboratory studies have suggested an additional “indirect” nighttime channel OH(v)) ⇒ O(1D)) ⇒ N2(v)) ⇒ CO2(v3)) ⇒ 4.3 μm of this energy transfer. We implemented this new channel in our non-LTE (non-Local Thermodynamic Equilibrium) model and show that, for various latitudinal and seasonal scenarios, including this additional channel brings differences between simulated and measured nighttime SABER 4.3 μm limb radiances to (−20, +30) %. These results confirm the important role of the new mechanism as a source of the nighttime 4.3 μm emission. This finding creates new opportunities for the application of CO2 4.3 μm observations in the study of the energetics and dynamics of the nighttime MLT.

Citation: Panka, P. A., Kutepov, A. A., Kalogerakis, K. S., Janches, D., Russell, J. M., Rezac, L., Feofilov, A. G., Mlynczak, M. G., and Yiğit, E.: Resolving the mesospheric nighttime 4.3 μm emission puzzle: New model calculations improve agreement with SABER observations, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-766, in review, 2016.
Peter A. Panka et al.
Peter A. Panka et al.
Peter A. Panka et al.

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Short summary
Recently, theoretical and laboratory studies have suggested an additional night-time channel of transfer of vibrational energy of OH molecules to CO2 in the mesosphere and lower thermosphere (MLT). We show that new mechanism brings modelled 4.3 micron emissions very close to the SABER/TIMED measurements. This renders new opportunities for the application of the CO2 4.3 micron observations in the study of the energetics and dynamics of the night-time MLT.
Recently, theoretical and laboratory studies have suggested an additional night-time channel of...
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