Front related model evaluation of multi-year simulations from hydrostatic to convection-permitting scales in the greater Alpine region

Atmospheric fronts play a major role in day-to-day life and are well known for sharp changes in local weather conditions. In mountainous regions, the interaction between fronts and the orography supports the development of characteristic precipitation patterns and may even cause specific weather phenomena, like thunderstorms, föhn events, and others. It is therefore an interesting question, how such fronts evolve in the next few days or how they will behave under changing climate conditions.

However, due to the complexity of fronts and limitations in numerical weather prediction or climate models, state-of-the-art automated front detection algorithms are largely restricted to the model they are applied onto. In particular, the outcome of these algorithms depends the discretization scheme of the underlying model (e.g. the grid spacing) and hence they may fail in model intercomparison or evaluation studies when data is given in various different grids.

In the present work, a diagnostic front detection algorithm, that is designed to overcome such model dependencies, is introduced and its applicability for model intercomparison is demonstrated by means of simple analytic test functions and idealized simulations of a baroclinic wave (i.e. the Jablonowksi and Williamson test) conducted with MPAS (60 km and 15 km grid spacing). Finally, the algorithm is exemplarily applied onto latest WRF evaluation simulations (15 km and 3 km grid spacing) from the CORDEX-FPS Convection initiative and the Integrated Forecast System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF) (~25 km grid spacing) to investigate differences in front statistics in the greater Alpine region of the period 2006 to 2009.

The study is funded by the Austrian Klima- und Energiefonds through the Austrian Climate Research Programme (ACRP) by means of the project "Research for Climate Protection: Value-adding Convection-Permitting Climate Simulations Austria" (reclip:convex, project id: B769999).