Dual Radiosonde Soundings of Gravity Wave Breaking over the Alps during the 2025 Winter TEAMx Observational Campaign

The TEAMx programme provides us with a unique observational data set which is extensive in spatial and temporal coverage and encompasses a diverse range of measurement techniques. A campaign such as this is ideal for studying the fine-scale behaviour of orographic gravity waves, including their generation, propagation and eventual breaking. As future weather and climate models are run at progressively higher resolutions, it is critical that these waves are simulated accurately across all spatial scales. Notably, regions of high vertical wind shear can lead to errors in the modelled behaviour of these waves which cause misrepresentations in both the altitude and magnitude of gravity wave drag. Furthermore, the partitioning between resolved and parameterised gravity wave drag should vary inversely across spatial scales and with consistency between different numerical models, such that the total drag remains constant. Whilst this is yet to be achieved, TEAMx has the potential to bring this closer to reality.

 

Here, we present results from the UK-funded TEAMx-FLOW project, which focuses on analysis of dual radiosonde launches during the winter extended observational period (wEOP). We analyse and quantify mountain wave momentum transport in these measurements, including using cross-spectral analysis of balloon pairs to obtain scale separation of observed waves. We also explore observations of partial wave breakdown in directionally sheared flow, a process which is not currently considered in parameterisation schemes. We will use our results to validate MetUM simulations, and hope that this research will be able to inform the development of scale-aware models in the future.