High-resolution LES studies of the turbulent exchange processes between forest and atmosphere under heterogeneous conditions
Responsible: Farah Kanani?
Project type: ​DFG research project with ​Universität Bayreuth and ​Max-Planck-Institut für Chemie Mainz
Duration: 1/12/2010-31/03/2014

Within the joint project EGER (ExchanGE processes in mountainous Regions) funded by the German Research Foundation (DFG), the effect of a forest edge on in-situ measurements of scalar fluxes of e.g. CO2, O3, temperature and humidity is studied. Using the parallelized LES model PALM enables us to study the scalar transport at a forest edge systematically for various meteorological and land surface conditions. The overall goal is to interpret the scalar flux measurements, which have been conducted during a field measurement from June to July 2011 in the Fichtelgebirge, Germany. The experiment was organized by the project partners at the University of Bayreuth, Germany and the Max-Planck Institute for Chemistry in Mainz, Germany.

In general, forests play an important role in the global ecosystem exchange. How well we can estimate this exchange as an input for climate models strongly depends on the quality of the flux measurements. Since the land surface becomes more and more heterogeneous due to land use, wind damage or pests, forests are often not continuous. Therefore, the landscape is characterized by sharp changes in surface conditions, like e.g. at forest edges. Because forest edges are well known to have a complex effect on the forest-atmosphere exchange, experimenters place their flux measurements close to forest edges to study these effects. But due to the lacking detailed knowledge of the near-edge exchange processes, the measurements are difficult to interpret.

Using PALM, we investigate in detail the scalar transport and the spatial variability of concentration and flux distributions within and above a forest downstream of a clearing-to-forest transition under different meteorological and plant physical conditions. Further interest is directed towards the investigation of transport processes at the lee-sided forest edge (forest-to-clearing transition). Results of these studies shall contribute to create a firm basic knowledge of the forest-atmosphere exchange in regions affected by a forest edge. This in turn is an essential prerequisite for being able to interpret scalar flux and concentration measurements in such regimes.