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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

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doi:10.5194/amt-2016-416
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
20 Jan 2017
Review status
This discussion paper is under review for the journal Atmospheric Measurement Techniques (AMT).
Comparison of Global Datasets of Sodium Densities in the Mesosphere and Lower Thermosphere from GOMOS, SCIAMACHY and OSIRIS Measurements and WACCM Model Simulations from 2008 to 2012
Martin P. Langowski1, Christian von Savigny1, John P. Burrows2, Didier Fussen3, Erin C. M. Dawkins4,5, Wuhu Feng6,7, John M. C. Plane6, and Daniel R. Marsh8 1Institute of Physics, Ernst-Moritz-Arndt-University of Greifswald, Greifswald, Germany
2Institute of Environmental Physics, University of Bremen, Bremen, Germany
3Belgian Institute for Space Aeronomy, Brussels, Belgium
4NASA Goddard Space Flight Center, Greenbelt, MD, USA
5Department of Physics, Catholic University of America, Washington, DC, USA
6School of Chemistry, University of Leeds, Leeds, UK
7National Center for Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK
8National Center for Atmospheric Research, Boulder, CO, USA
Abstract. During the last decade, multiple limb sounding satellites have measured the global sodium (Na) number densities in the mesosphere and lower thermosphere (MLT).Datasets are now available from GOMOS, SCIAMACHY (both on Envisat) and OSIRIS/Odin. Furthermore, global model simulations of the Na layer in the MLT simulated with WACCM-Na are available. In this paper, we compare these global datasets. Globally, there is an agreement in the observed and simulated monthly average of Na vertical column densities that were compared with each other. They show a clear seasonal cycle with a summer minimum most pronounced at the poles. They also show signs of a semi-annual oscillation in the equatorial region. The vertical column densities vary between 0.5 × 109 cm−2 to 7 × 109 cm−2 near the poles and between 3 × 109 cm−2 to 4 × 109 cm−2 at the equator. The phase of the seasonal cycle and semi-annual oscillation shows small differences between the different instruments. The full width at half maximum of the profiles is 10 to 16 km for most latitudes, but significantly smaller in the polar summer. The centroid altitudes of the measured sodium profiles range from 89 to 95 km, while the model shows on average 2 to 4 km lower centroid altitudes. This coincides with a 3 km lower mesopause altitude in the WACCM simulations compared to measurements, which may be the reason for the low centroid altitudes. Despite this global 2 to 4 km shift, the model captures latitudinal and temporal variations. The variation of the WACCM dataset during the year at different latitudes is similar to the one of the measurements. Furthermore, the differences between the measured profiles with different instruments and therefore different local times are also present in the model simulated profiles. This capturing of latitutinal and temporal variations is also found for the vertical column densities and profile widths.

Citation: Langowski, M. P., von Savigny, C., Burrows, J. P., Fussen, D., Dawkins, E. C. M., Feng, W., Plane, J. M. C., and Marsh, D. R.: Comparison of Global Datasets of Sodium Densities in the Mesosphere and Lower Thermosphere from GOMOS, SCIAMACHY and OSIRIS Measurements and WACCM Model Simulations from 2008 to 2012, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-416, in review, 2017.
Martin P. Langowski et al.
Martin P. Langowski et al.
Martin P. Langowski et al.

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Short summary
Meteoric metals form metal layers in the upper atmosphere and play a role in the formation of middle atmospheric clouds and aerosols. The total metal influx rate is not well known, though. Global Na datasets from measurements and a model are available, which haven't been compared yet on a global scale, which is done in this paper. Overall the agreement is good and many differences between measurements are also found in the model simulations. The modeled layer altitude is too low, though.
Meteoric metals form metal layers in the upper atmosphere and play a role in the formation of...
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