Optimization of the geopotential heights information used in a rainfall-based weather patterns classification over Austria

Classifications of atmospheric circulation patterns are useful tools to improve the description of the climate of a given region and the analysis of meteorological situations. In particular, weather pattern (WP) classifications could be used to improve the description of spatial heavy rainfall. Here, a bottom-up approach, previously used to build WP classification in France, is applied for the definition of a WP classification useful for the description of Austrian heavy rainfall. The optimal spatial extent and the optimal position of the geopotential fields to be taken into account for a WP classification is studied. The proposed WP classification is shown to be coherent with the general knowledge on synoptic situations responsible for heavy rainfall over Austria. Moreover, the classification has good performances in terms of heavy rainfall spatial description compared to 152 COST 733 classifications defined in the same region. In particular, we show that the choice of spatial extent of the geopotential fields, their position and their characteristics is relevant for capturing physical information on synoptic situations responsible for heavy rainfall and that it can improve WP classification performances. Copyright (c) 2012 Royal Meteorological Society