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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 36, issue 2
Ann. Geophys., 36, 541-553, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Ann. Geophys., 36, 541-553, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Regular paper 03 Apr 2018

Regular paper | 03 Apr 2018

New results on the mid-latitude midnight temperature maximum

Rafael L. A. Mesquita1, John W. Meriwether1, Jonathan J. Makela2, Daniel J. Fisher2, Brian J. Harding2, Samuel C. Sanders1, Fasil Tesema3, and Aaron J. Ridley4 Rafael L. A. Mesquita et al.
  • 1Physics and Astronomy Department, Clemson University, Clemson, South Carolina, USA
  • 2Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
  • 3Washera Geospace and Radar Science Laboratory, Bahir Dar University, Bahir Dar, Ethiopia
  • 4Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA

Abstract. Fabry–Perot interferometer (FPI) measurements of thermospheric temperatures and winds show the detection and successful determination of the latitudinal distribution of the midnight temperature maximum (MTM) in the continental mid-eastern United States. These results were obtained through the operation of the five FPI observatories in the North American Thermosphere Ionosphere Observing Network (NATION) located at the Pisgah Astronomic Research Institute (PAR) (35.2°N, 82.8°W), Virginia Tech (VTI) (37.2°N, 80.4°W), Eastern Kentucky University (EKU) (37.8°N, 84.3°W), Urbana-Champaign (UAO) (40.2°N, 88.2°W), and Ann Arbor (ANN) (42.3°N, 83.8°W). A new approach for analyzing the MTM phenomenon is developed, which features the combination of a method of harmonic thermal background removal followed by a 2-D inversion algorithm to generate sequential 2-D temperature residual maps at 30min intervals. The simultaneous study of the temperature data from these FPI stations represents a novel analysis of the MTM and its large-scale latitudinal and longitudinal structure. The major finding in examining these maps is the frequent detection of a secondary MTM peak occurring during the early evening hours, nearly 4.5h prior to the timing of the primary MTM peak that generally appears after midnight. The analysis of these observations shows a strong night-to-night variability for this double-peaked MTM structure. A statistical study of the behavior of the MTM events was carried out to determine the extent of this variability with regard to the seasonal and latitudinal dependence. The results show the presence of the MTM peak(s) in 106 out of the 472 determinable nights (when the MTM presence, or lack thereof, can be determined with certainty in the data set) selected for analysis (22%) out of the total of 846 nights available. The MTM feature is seen to appear slightly more often during the summer (27%), followed by fall (22%), winter (20%), and spring (18%). Also seen is a northwestward propagation of the MTM signature with a latitude-dependent amplitude. This behavior suggests either a latitudinal dependence of thermosphere tidal dissipation or a night-to-night variation of the composition of the higher-order tidal modes that contribute to the production of the MTM peak at mid-latitudes. Also presented in this paper is the perturbation on the divergence of the wind fields, which is associated with the passage of each MTM peak analyzed with the 2-D interpolation.

Publications Copernicus
Short summary
The midnight temperature maximum (MTM) is a phenomenon resulting from the constructive interference of the atmospheric tides. This paper brings the analysis of a long data set (846 nights) from the NATION network along with new analysis techniques (harmonic background removal and 2-D temperature interpolation) to detect the MTM in the mid-latitude range.
The midnight temperature maximum (MTM) is a phenomenon resulting from the constructive...