In January and February 2016, the OH airglow camera system FAIM (Fast Airglow
Imager) measured during six flights on board the research aircraft FALCON in
northern Scandinavia. Flight 1 (14 January 2016) covering the same ground
track in several flight legs and flight 5 (28 January 2016) along the
shoreline of Norway are discussed in detail in this study. The images of the
OH airglow intensity are analysed with a two-dimensional FFT regarding
horizontal periodic structures between 3 and 26 km horizontal wavelength and
their direction of propagation. Two ground-based spectrometers (GRIPS,
Ground-based Infrared P-branch Spectrometer) provided OH airglow
temperatures. One was placed at ALOMAR, Northern Norway (Arctic Lidar
Observatory for Middle Atmosphere Research; 69.28∘ N,
16.01∘ E) and the other one at Kiruna, northern Sweden
(67.86∘ N, 20.24∘ E). Especially during the last third of
January 2016, the weather conditions at Kiruna were good enough for the
computation of nightly means of gravity wave potential energy density.
Coincident TIMED-SABER (Thermosphere Ionosphere Mesosphere Energetics
Dynamics–Sounding of the Atmosphere using Broadband Emission Radiometry)
measurements complete the data set. They allow for the derivation of
information about the Brunt–Väisälä frequency and about the
height of the OH airglow layer as well as its thickness.
The data are analysed with respect to the temporal and spatial evolution of
mesopause gravity wave activity just before a minor stratospheric warming at
the end of January 2016. Wave events with periods longer (shorter) than
60 min might mainly be generated in the troposphere (at or above the height
of the stratospheric jet). Special emphasis is placed on small-scale
signatures, i.e. on ripples, which may be signatures of local instability
and which may be related to a step in a wave-breaking process. The most
mountainous regions are characterized by the highest occurrence rate of
wave-like structures in both flights.</p