The overarching goal of the three-year DFG-WEAVE project GIGAWATT (Ground-based investigation of Gravity Waves with Airglow and Wind measurements by Applying Tomographic Techniques) is to achieve a better and deeper understanding of gravity waves in the middle atmosphere in the Alpine region by combining different and complementary operational measurement systems. In the future, the results can be used for a better parameterisation of gravity waves in models. The project is being carried out in collaboration with the University of Bern and the University of Augsburg.
The University of Bern uses temperature radiometers (TEMPERA-C) and wind radiometers (WIRA-C), which provide information on the vertical temperature and wind gradients over Bern, as well as a meteor wind radar, which makes it possible to detect the wind in the 80-100km altitude range. DLR uses an airglow camera (FAIM - Fast Airglow IMager) with a scanning mechanism, which allows it to "scan" the sky over from horizon to horizon in order to achieve a large spatial coverage with high spatial resolution at the same time. This allows horizontal gravity wave parameters, which can be seen in the OH-airglow, to be determined in the corresponding altitude layer around 86km. The field-of-view in spans a diameter of 500km by a spatial resolution of approx. 200-300m per pixel. This "Scan-FAIM" developed by EOC will be set up near Bern as part of the project. Together with another similar instrument at the DLR in Oberpfaffenhofen, it will cover a large part of the Alpine region at the height of the OH airglow layer at an altitude of 86 kilometres (see the map).
The 500km diameter field of views of the Scan-FAIM instruments in Oberpfaffenhofen and Bern in light and dark turquoise, respetively.
The field of view of the meteor wind radar is shown in brown. The radiometers provide the vertical temperature and wind gradients above the University of Bern. The orography of the Alps is shown in shades of grey.
One innovative aspect of the project is the simultaneous use of numerous complementary measuring systems to record various atmospheric parameters and the use of tomographic methods to utilise this data even more effectively. Tomography can be used to derive horizontal wave parameters from the meteor wind radar measurements, while the airglow camera measurements can be used to determine vertical wave parameters that cannot be derived in any other way in this extent. In the case of the scan-FAIM instruments, the area of the overlapping volume between the two scan-FAIM instruments is used for this purpose.
In addition to setting up and operating the instruments, the project will also focus on analysing the three-dimensional data and combining the various atmospheric parameters. The complementary data will also allow the tomographic algorithms to be mutually validated. The extensive three-dimensional information about the gravity waves allows the source of the waves to be estimated using ray tracing. Due to the long-term operation of the instruments and the resulting multi-year data, systematics can be derived which can be used, among other things, for better parameterisation of small-scale gravity waves in models and a deeper understanding of gravity wave physics.
Image of the OH airglow layer at an altitude of 86km with a diameter of 500km above Oberpfaffenhofen (OPN), composed of 35 individual images.
The field of view to date already covers a large part of southern Germany and the western part of Austria. Numerous gravity wave structures on scales from a few kilometres to a few hundred kilometres can be seen.
