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Volume 9, issue 1 | Copyright

Special issue: Limb observations of the middle atmosphere by space- and airborne...

Atmos. Meas. Tech., 9, 295-311, 2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 28 Jan 2016

Research article | 28 Jan 2016

Retrieval of sodium number density profiles in the mesosphere and lower thermosphere from SCIAMACHY limb emission measurements

M. P. Langowski1,2, C. von Savigny2, J. P. Burrows1, V. V. Rozanov1, T. Dunker3, U.-P. Hoppe3, M. Sinnhuber4, and A. C. Aikin5 M. P. Langowski et al.
  • 1Institut für Umweltphysik, Universität Bremen, Bremen, Germany
  • 2Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, Greifswald, Germany
  • 3Department of Physics and Technology, UiT The Arctic University of Norway, Tromsø, Norway
  • 4Institut für Meteorologie und Klimaforschung – Atmosphärische Spurengase und Fernerkundung, Karlsruhe Institute of Technology, Karlsruhe, Germany
  • 5The Catholic University of America, Washington DC, USA

Abstract. An algorithm has been developed for the retrieval of sodium atom (Na) number density on a latitude and altitude grid from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) limb measurements of the Na resonance fluorescence. The results are obtained between 50 and 150km altitude and the resulting global seasonal variations of Na are analyzed. The retrieval approach is adapted from that used for the retrieval of magnesium atom (Mg) and magnesium ion (Mg+) number density profiles recently reported by Langowski et al. (2014). Monthly mean values of Na are presented as a function of altitude and latitude. This data set was retrieved from the 4years of spectroscopic limb data of the SCIAMACHY mesosphere and lower thermosphere (MLT) measurement mode (mid-2008 to early 2012).

The Na layer has a nearly constant peak altitude of 90–93km for all latitudes and seasons, and has a full width at half maximum of 5–15km. Small but significant seasonal variations in Na are identified for latitudes less than 40°, where the maximum Na number densities are 3000–4000atoms cm−3. At middle to high latitudes a clear seasonal variation with a winter maximum of up to 6000atoms cm−3 is observed. The high latitudes, which are only measured in the summer hemisphere, have lower number densities, with peak densities being approximately 1000Naatoms cm−3. The full width at half maximum of the peak varies strongly at high latitudes and is 5km near the polar summer mesopause, while it exceeds 10km at lower latitudes. In summer the Na atom concentration at high latitudes and at altitudes below 88km is significantly smaller than that at middle latitudes. The results are compared with other observations and models and there is overall a good agreement with these.

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An algorithm has been developed for the retrieval of sodium atom (Na) number density on a latitude and altitude grid from SCIAMACHY limb measurements of the Na resonance fluorescence (multiannual means 2008–2012). The Na layer peaks at 90 to 93 km altitude and has a FWHM of 5 to 15 km. A summer minimum in peak density and width is observed at high latitudes. At low latitudes, a semiannual oscillation is found. The results are compared with other measurements and models and agree well with these.
An algorithm has been developed for the retrieval of sodium atom (Na) number density on a...