Footprint model development and validation for homogeneous and inhomogeneous terrain using high resolution large eddy simulation

• Applicants: Professor Dr. Thomas Foken; Professor Dr. Siegfried Raasch
• Subject Area: Atmospheric Science
• Term: from 2005 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5452157

The project focuses on developing and validating methods to compute footprints of atmospheric constituents above thermally and aerodynamically heterogeneous surfaces. A footprint function determines the spatial context of a measurement by defining a transfer function between sources or sinks of the constituent and the sensor position. The resulting source area is an important quality assessment tool, e.g. to assess the influence of variable terrain elements on the data. Although micrometeorological research focuses increasingly on complex terrain, footprint models developed to date are restricted to idealised cases of horizontally homogeneous flow conditions, and thus cannot consider the impact of heterogeneity. In the framework of this project, one means to consider influence of heterogeneity is a highresolution large eddy simulation (LES) model that allows the explicit resolution of the turbulent transport processes. As a second, computationally less costly method, both forward and backward Lagrangian stochastic (LS) algorithms are modified to account for horizontally heterogeneous flow conditions. The LES datasets will be used both to derive the flow statistics required to run the LS models, and to evaluate their produced source areas. The applicability of the footprint estimates from both LES model and LS algorithms will finally be assessed with data from field experiments.

• DFG Programme: Research Grants