Alpine gravity waves: Lessons from MAP regarding mountain wave generation and breaking

The two-month special observing period of the Mesoscale Alpine Programme (MAP) in autumn 1999 included a variety of complex mountain wave events. Seven wave events were carefully analyzed, compared with numerical models and described in published papers. These detailed investigations revealed some common dynamical elements, i.e. the importance of low-level processes involving the slow-moving boundary layer, low-level wind shear causing either wave absorption or decoupling/spilling, upstream blocking, and latent heat release. Based on these studies, it is clear that any quantitative prediction of mountain wave generation must take full account of these lower troposphere processes. The newest numerical models show significant skill in simulating these effects. Using these models, the climatology of waves over the Alps can be studied. Copyright (c) 2007 Royal Meteorological Society.