Comparison of conventional Lagrangian stochastic footprint models against LES driven footprint estimates 1Department of Micrometeorology, University of Bayreuth, 95440 Bayreuth, Germany
3Institut für Meteorologie und Klimatologie, Leibniz Universität Hannover, Hannover, Germany
4Department of Geography, Swansea University, Singleton Park, Swansea, Wales UK
*current address: Finnish Meteorological Institute, Climate and Global Change Research, P.O. Box 503, 00101 Helsinki, Finland
**current address: Department of Physics, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
Received: 29 Oct 2008 – Published in Atmos. Chem. Phys. Discuss.: 09 Feb 2009 – Published: 06 Aug 2009Abstract. In this study we introduce a comparison method for footprint model results
by evaluating the performance of conventional Lagrangian stochastic (LS) footprint
models that use parameterised flow field characteristics with results of a Lagrangian
trajectory model embedded in a large eddy simulation (LES) framework. The two conventional models follow
the particles backward and forward in time while the trajectories in LES only
evolve forward in time. We assess their performance in two unstably stratified boundary layers
at observation levels covering the whole depth of the atmospheric boundary layer.
We present a concept for footprint model comparison that can be applied for 2-D
footprints and demonstrate that comparison of only cross wind integrated
footprints is not sufficient for purposes facilitating two dimensional footprint information.
Because the flow field description among the three models is most realistic
in LES we use those results as the reference in the comparison.
We found that the agreement of the two conventional models against the LES
is generally better for intermediate measurement heights and for the more
unstable case, whereas the two conventional flux footprint models agree best
under less unstable conditions. The model comparison in 2-D was found quite
sensitive to the grid resolution.
Citation: Markkanen, T., Steinfeld, G., Kljun, N., Raasch, S., and Foken, T.: Comparison of conventional Lagrangian stochastic footprint models against LES driven footprint estimates, Atmos. Chem. Phys., 9, 5575-5586, doi:10.5194/acp-9-5575-2009, 2009.