Graz Lagrangian Model

The high-resolution model system GRAMM/GRAL, developed at the Institute of Thermodynamics and Sustainable Propulsion Systems at Graz University of Technology, has become a benchmark for dispersion modelling in urban areas, both in scientific research, as well as in regulatory assessments.


The model is especially suitable for low-wind speed conditions and complex terrain. An integrated micro-scale flow-field model takes the effect of buildings on pollutant dispersion into account.

The initial driver for the development of GRAL was the need for a model that could deal with the frequent low-wind-speed conditions (< 1.5 m s-1 for up to 90 per cent of the time) in the inner-Alpine basins of Austria. Another important feature of GRAL is the ability to deal with the dispersion of pollutants emitted from road tunnel portals. A series of national research projects resulted in a new physical modelling approach for use in GRAL, and this approach is still unique among dispersion models. See all features.

GRAL model system is a freeware and can be downloaded on this website. The GRAL code is available under the GNU/GPL 3 licence:

It is also possible to book a training.

Special Thanks to Markus Kuntner and Dietmar Öttl!