Banner Cloud Dynamics: Steps Towards a Theory and Simulations With Realistic Orography

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Banner clouds are clouds in the lee of high mountains or steep ridges. Current wisdom explains their formation as mainly due to forced uplift in the rising branch of a lee vortex. An earlier project funded by the DFG revealed some basic insight. This was acheived on the one hand through detailed observations at Mount Zugspitze, which allowed for the first time to systematically characterize this cloud type. On ther other hand, simulations with the help of a Large Eddy Simulation model shed new light on formation mechanisms. The current project aims to take advantage of this earlier project and further our knowledge in a twofold way. First it is planned to carry through simulations with realistic orography (instead of idealized pyramid-shaped orography). This allows comparison with a wealth of observational data from the earlier DFG project. Second, it is planned to work towards a theory of banner cloud formation. The latter will be based on systematic sets of numerical simulations using the well-established model setup.