Penetration and Interruption of Alpine Foehn
Downslope windstorms represent one of the greatest weather hazards in mountainous regions. Alpine foehn is a key example of these types of windstorms. During the last decades, the scientific community has put ongoing effort into better understanding and predicting these severe winds. However, previous research has primarily focused on the well-developed stage rather than the complex initial and final stages of foehn. Hence, the mechanisms of foehn penetration into valleys and of foehn breakdown are still poorly understood. However, these transient stages have the greatest implications for aviation safety and air quality in the valley. Breakthrough and decay of foehn are controlled by various atmospheric processes. Some of the previous studies disagree on which of these processes are dominant. Furthermore, foehn poses a great challenge for numerical weather prediction models. Forecast errors are partly related to deficiencies in correctly capturing these processes.
The goal of this research project is to improve the understanding of atmospheric processes that govern the breakthrough and decay of foehn. Our methodology is based on a combination of sophisticated measurement techniques and computer simulations. A key element of the project is a field experiment that will be conducted in Innsbruck (Inn Valley, Austria) and its surroundings. The most important atmospheric observing systems are three combined laser-based instruments (so-called lidars) to remotely measure the turbulent flow field in the valley as well as a research aircraft to observe the airflow at flight level. To fill the spatial gaps of the measurement systems, the airflow will be simulated with a computer model (Weather Research and Forecasting Model). Observations and simulations will be used to quantify all relevant atmospheric processes. The computer model will not only be used for real-case studies but also as a virtual laboratory to valuate the sensitivity of foehn onset and decay to various factors. The aim of the project is to compile a comprehensive picture of different prototypes of foehn development. The outcome of the project will be beneficial for improving the forecast skill of numerical weather prediction models over complex terrain. This, in turn, will improve severe turbulence and air pollution warnings.
Austrian Science Fund (FWF): P29746-N32 0 (https://www.fwf.ac.at/)
Weiss Science Foundation (http://www.weiss-wissenschaftsstiftung.at)
University of Innsbruck
01/03/2017 to 28/02/2021