FERUS - Footprint Estimation over Rough Urban Surfaces
When measuring concentrations or turbulent fluxes of atmospheric pollutants (but also water vapour or even heat) it is most often of crucial interest which portion of the upwind surface area has contributed to what degree to this measurement. This upwind surface influence area is called "footprint" and depends on the measurement site (e.g., measurement height, nearby surface characteristics) and the atmospheric state. Footprint models of different sophistication are available - ranging from simple "analytical" models to computing time consuming LES modelling approaches. Despite the apparent need for pollutant source appointment in urban areas, there are almost no footprint models available that specifically would take into account the dispersion characteristics in the urban atmosphere, because they were originally designed for flat areas. Those few that do take the urban atmosphere into account require excessive computational power and are therefore unsuited for routine operation. FERUS aims at creating a computationally faster model designed for urban footprints.
Turbulence, and hence dispersion characteristics in the lowest tens to hundreds of meters over an urban surface are strongly influenced by the presence of buildings and other structures, their spatial distribution, density and height. Knowledge on this turbulence structure near urban surfaces and from urban pollutant dispersion modelling will be used for the development of an "urban footprint model". This model will be tested using urban tracer release experiments and recent measurements on the roof of the university building. Finally, the urban footprint model will be generalized to other "rough surfaces", for example forested surfaces.
Natascha Kljun, University of Swansea (UK)
Austrian Research Funding Agency, FWF: project P 30017-NBL (Supported by Tyrolean Research Funds)