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

旗云是在高山或陡峭山脊的背风处的云。目前的智慧解释了它们的形成主要是由于背风漩涡上升分支的强迫隆起。由DFG资助的早期项目揭示了一些基本的见解。这一方面是通过在楚格峰的详细观测实现的，这使得第一次系统地描述了这种云的类型。另一方面，在大涡模拟模型的帮助下进行的模拟揭示了形成机制的新曙光。目前的项目旨在利用这个早期的项目，并以双重方式进一步了解我们的知识。首先，计划对现实地形进行模拟（而不是理想化的金字塔形地形）。这样就可以与早期DFG项目的大量观测数据进行比较。第二，计划对旗云形成理论进行研究。后者将基于使用已建立的模型设置的系统数值模拟集。

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.