A GRey-zone Ensemble Analysis for TEAMx

• Applicants: Dr. Jan Keller; Dr. Annika Oertel
• Subject Area: Atmospheric Science
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563995249

The TEAMx meteorological field campaign in the Alps in 2024-25 will deliver observations of the mountain boundary layer at unprecedented detail. The campaign follows a seamless observation strategy to monitor atmospheric motions across the meso- and microscales in a transect across the Inn Valley in Austria and the Adige Valley in Italy. Gaps between point measurements, such as weather stations and eddy covariance sites, are filled with continuous high-frequency observations from dozens of remote-sensing platforms (e.g., Doppler wind lidars and water vapor lidars), both ground-based and airborne. In the current practice, however, such field observations are integrated only qualitatively, but not merged into a consistent dataset, such that the information content of the expensive measurements is often not fully exploited by the scientific community. This project aims at distilling information from the wide array of TEAMx special observations into an easy-to-use consensus dataset, the TEAMx analysis. This is a gridded 4D estimate of the evolving atmospheric state at sub-hourly and sub-km resolution, covering the target areas during intensive observation periods. It will be used by the TEAMx community (about 100 scientists worldwide) for various interconnected research purposes. The computation of the TEAMx analysis relies on ensemble simulations with the ICON numerical weather prediction (NWP) model and on the KENDA convective-scale ensemble data assimilation (DA) system. These tools are used for km-scale operational NWP at the German and Swiss national weather services. Here, they are used for the first time to produce analyses at 500- and 125-m mesh size. Such resolutions lie within the so-called turbulence grey zone, which is the operational range of next-generation NWP systems, and in which no best practice for turbulence parameterization exists yet. Much of the planned research consists in improving the DA algorithms to enable analysis runs at grey-zone resolutions. The key challenges lie in representing the background and observation errors in the most effective way, and in mitigating the impacts of several sources of sub- optimality (e.g., systematic model errors) on the assimilation. The design of an effective method for producing campaign analyses at sub-km resolution is long overdue. The TEAMx gridded campaign analysis will be the first of its kind and will serve as a blueprint for many future campaigns. The partnership includes leading Austrian and German universities in the field of atmospheric sciences, as well as the research departments of the German and Swiss national weather services.

• DFG Programme: Research Grants
• International Connection: Austria, Switzerland
• Partner Organisation: Schweizerischer Nationalfonds (SNF)
• Co-Investigator: Professor Dr. Peter Knippertz
• Cooperation Partners: Dr. Marco Arpagaus; Professor Dr. Mathias Rotach; Dr. Stefano Serafin; Professor Dr. Martin Weissmann