A refined model of the influence of orography on the mesoscale distribution of extreme precipitation

Abstract

This paper briefly summarizes the results of a four-year research project carried out for the Federal Ministry of Agriculture and Forestry in Vienna, Austria. The main objective was the development of a deterministic model for the estimation of the distribution of extreme precipitation in complex terrain. The orographic component of precipitation is conceptually divided into a part directly generated by dynamic uplift and a part originating from convective activity. The model for the first type of precipitation enhancement is based on the theory of linear two-dimensional air flow over mountains. A dynamically consistent flow field and explicit simulation of the seeder-feeder mechanism are the main improvements compared to an earlier version of this model (Haiden et al., 1990). The assessment of convective precipitation is based on a new parameterization using results of an analytical model of thermally induced upslope flow. A comparison of model results with observations shows reasonable agreement regarding the structure of the precipitation fields.