The OH-airglow layer in about 87 km altitude is well-suited for the investigation of atmospheric dynamics, allowing continuous observations of the night-sky throughout the year. Especially, atmospheric gravity waves are prominent features in the data of airglow imaging systems.

Our imaging system FAIM 1 (Fast Airglow IMager 1) focusses on small-scale wave-like structures in the horizontal wavelength range of 1 km to 50 km at mesopause heights. This range covers small-scale gravity waves as well as larger scale instability structures and is rarely investigated in literature beyond case studies.

For FAIM 1 three years of measurements are available at present in a high temporal and spatial resolution. For the first year the instrument was located at Oberpfaffenhofen, Germany (48.087N, 10.280E) and for another 1.5 years it was set-up at Sonnblick Observatory, Austria (47.054N, 12.958E). To analyse the vast amount of image data, the two-dimensional FFT is used for extracting the wave parameters. For both stations, the dominant horizontal wavelengths and main propagation directions are retrieved; the similarities and differences are presented and discussed as well as a seasonal relationship.

This work received funding from the Bavarian State Ministry of the Environment and Consumer Protection.