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Annales Geophysicae Sun, Earth, planets, and planetary systems An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/angeo-2018-30
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Regular paper
05 Apr 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Annales Geophysicae (ANGEO).
On the short-term variability of turbulence and temperature in the winter mesosphere
Gerald A. Lehmacher1, Miguel F. Larsen1, Richard L. Collins2, Aroh Barjatya3, and Boris Strelnikov4 1Department of Physics & Astronomy, Clemson University, Clemson, South Carolina, USA
2Geophysical Institute, University of Alaska, Fairbanks, Alaska, USA
3Department of Physical Sciences, Embry-Riddle Aeronautical University, Daytona Beach, Florida, USA
4Leibniz-Institute for Atmospheric Physics, K├╝hlungsborn, Germany
Abstract. Four mesosphere-lower thermosphere temperature and turbulence profiles were obtained in situ within ~ 30 minutes and over an area of about 100 by 100 kilometers during a sounding rocket experiment conducted on January 26, 2015 at Poker Flat Research Range in Alaska. Using active payload attitude control, neutral density fluctuations, a tracer for turbulence, were observed with very little interference from the payload spin motion, and with high precision (< 0.01 %) at sub-meter resolution. The large-scale vertical temperature structure was very consistent between the four soundings. The mesosphere was almost isothermal, which means more stratified, between 60 and 80 km, and again, between 88 and 95 km. The stratified regions adjoined quasi-adiabatic regions assumed to be well mixed. Additional evidence for vertical transport and convective activity comes from sodium densities and trimethyl aluminum trail development, respectively, which were both observed simultaneously with the in situ measurements. We found considerable kilometer scale temperature variability with amplitudes of 20 K in the stratified region below 80 km. Several thin turbulent layers were embedded in this region, differing in width and altitude for each profile. Energy dissipation rates varied between 0.1 and 10 mW/kg, which is typical for the winter mesosphere. Very little turbulence was observed above 82 km, consistent with very weak small-scale gravity wave activity in the upper mesosphere during the launch night. On the other hand, above the cold and prominent mesopause at 102 km, large temperature excursions of +40 K to +70 K were observed. Simultaneous wind measurements revealed extreme wind shears near 108 km, and combined with the observed temperature gradient, isolated regions of unstable Richardson numbers (0 < Ri < 0.25) were detected in the lower thermosphere. The experiment was launched into a bright auroral arc under moderately disturbed conditions (Kp ~ 5).
Citation: Lehmacher, G. A., Larsen, M. F., Collins, R. L., Barjatya, A., and Strelnikov, B.: On the short-term variability of turbulence and temperature in the winter mesosphere, Ann. Geophys. Discuss., https://doi.org/10.5194/angeo-2018-30, in review, 2018.
Gerald A. Lehmacher et al.
Gerald A. Lehmacher et al.
Gerald A. Lehmacher et al.

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Short summary
We used sounding rockets to obtain 4 high-resolution profiles in the mesosphere over a limited area. We found consistent deep isothermal and adiabatic layers, but variable and finely structured turbulence preferentially in the lower stable mesosphere. Accompanying tracer releases showed horizontal winds in the lower thermosphere with extreme shears and 200 m/s winds under moderately disturbed geomagnetic conditions, and convective structures just below the mesopause.
We used sounding rockets to obtain 4 high-resolution profiles in the mesosphere over a limited...
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