Atmospheric transport modelling in mountainous regions using very high resolution meteorological simulations

Air quality conditions in Alpine regions are strongly influenced by their complex topography. Local wind systems, steep slopes and narrow valleys, seldom wider than a few kilometers, enhance accumulation of pollutants. These conditions are challenging for both, meteorological as well as atmospheric dispersion models, since higher resolutions, resulting in steeper model surfaces, are required.

A case study to evaluate how transport in mountainous regions can be better resolved is carried out. For two mountainous stations, one located on an Alpine valley floor (Innsbruck, Alps, Austria) and the other one on a mountain top (Schauinsland, Black Forest, Germany), meteorological simulations with WRF and MM5 are performed with grid spacings down to 0.2 km. Model output is then used to feed the Lagrangian particle dispersion model FLEXPART (MM5V3.7-FLEPXARTv6.2 and FLEXPART-WRF versions) used in backward mode for selected observation stations. The resulting dispersion calculations are compared with results obtained with coarse driving data (ECMWF, 0.75 degree), also used as boundary conditions and initial conditions for the two mesoscale models. Additionally, dispersion calculations, if folded with the appropriate emission inventory, can be directly compared with monitoring data at the stations.

Acknowledgements: This work is part of the HiRmod project, funded by the Austrian Climate and Energy Fund through the Austrian Climate Research Programme.