Ground-based investigation of gravity waves with airglow and wind measurements by applying tomographic techniques

• Applicants: Professor Dr. Michael Bittner; Privatdozentin Dr. Sabine Wüst
• Subject Area: Atmospheric Science
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 540878795

Atmospheric waves are crucial drivers of the energetic coupling between different layers in the atmosphere. At the mesosphere/lower thermosphere (MLT), this wave-driven circulation results in a deviation of the summer mesopause temperatures of up to 100K from the radiatively determined equilibrium, making the polar summer mesopause the coldest region on Earth. Gravity waves and their intermittent sources at lower altitudes seem to be an essential driver of this wave-driven residual circulation. Planetary waves and tides are also important for the vertical gravity-wave (GW) coupling as they cause a spatial and temporal variable background flow field altering the vertical propagation conditions of GWs due to critical level filtering. Direct numerical simulations suggest that the horizontal wavelengths between 30km and 300km are contributing most significantly to the momentum budget and the energy deposition of breaking GWs. Furthermore, recent model studies emphasize the relevance of secondary wave generation for the momentum budget at the MLT. In this proposal, we plan to combine unique observational techniques to establish a high-resolution GW observatory for the alpine region 1) to characterize the large-scale temperature and wind structure using state-of-the-art temperature (TEMPERA-C) and wind (WIRA-C) radiometers in the stratosphere and lower mesosphere to detect potential critical level filtering or secondary wave generation and 2) to perform high-resolution tomographic retrievals from OH airglow FAIM cameras using multi-static observations resolving small-scale GWs in the horizontal wavelength range between 1km and 200km over the alpine region and with a temporal resolution in the order of few minutes. These observations are going to be complemented by a Swiss meteor radar and radiometric winds at the OH airglow layer to derive intrinsic GW properties. The proposed combination of various remote sensing techniques facilitates unprecedented observations of GWs covering the most relevant scales at the MLT. The wind and temperature radiometers are going to characterize the vertical propagation conditions at the stratosphere and lower mesosphere and provide continuous background information for the vertical GW propagation. The tomographic FAIM airglow analysis will resolve the 3D GW structure within the airglow layer, which together with the wind information from the meteor radar and the radiometer opens new possibilities to derive the intrinsic GW parameters with high precision and to verify the results with the GW dispersion relations from the linear GW theory.

• DFG Programme: Research Grants
• International Connection: Switzerland
• Cooperation Partner: Privatdozent Dr. Gunter Stober