Turbulent Exchange Processes in and above tall Vegetation

This study presents first results of the complex turbulence structure during the experiment WALDATEM-2003 at the 'Weidenbrunnen' FLUXNET measuring site of the University of Bayreuth in the Fichtelgebirge mountains, 50° 09' N, 11° 52'E, 765 m a.s.l. over a 19 m high spruce forest. The turbulence structure of the wind vector, the temperature, water vapour and carbon dioxide concentration were studied using a wavelet tool. It was possible to separate high frequent turbulence from coherent structures and, during the night, also gravity waves. Additionally the turbulence structure in the lower atmospheric boundary layer was observed with a Sodar-RASS system. The nearly real-time analysis of the turbulence structure allowed an optimal handling of a whole air hyperbolic relaxed accumulation system to measure carbon dioxide and 13C isotope fluxes. Profile systems for wind, temperature, humidity and carbon dioxide and a horizontal gradient system for the measurement of advection and drainage flow were installed. The experiment allowed a complete overview of fluxes and turbulent exchange processes in forest – boundary layer system. First results are available for the similarity of different scalars and the decoupling and coupling between the canopy with the atmosphere.