Abstract. Four mesosphere–lower thermosphere temperature and turbulence
profiles were obtained in situ within ∼30 min and over an area of
about 100 by 100 km during a sounding rocket experiment conducted on
26 January 2015 at Poker Flat Research Range in Alaska. In this paper we
examine the spatial and temporal variability of mesospheric turbulence in
relationship to the static stability of the background atmosphere. 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 of 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−1, 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 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).
On the short-term variability of turbulence and temperature in the winter mesosphere