On the quality assurance of surface energy flux measurements

The first part of this study focuses on quality assessment tools for the eddy covariance method to determine turbulent fluxes out of high frequency time series of wind components and scalars. A comprehensive software package is presented, which includes all necessary transformations and corrections like planar-fit rotation, Schotanus-correction, Moore-correction, or WPL-correction. In addition, de-spiking procedures and cross-correlation test are realised, and the quality of the calculated fluxes is determined according to a procedure proposed by Foken and Wichura (1996). To check the spatial representativeness of specific measurement positions, a quality assessment tool using footprint analyses was applied to determine the composition of land use types in the source area. This system for quality assessment was successfully applied as the reference procedure for eddy covariance measurements over different types of land use during the experiment campaign LITFASS-2003. It is also a major component of the quality control programme for more than 100 flux monitoring sites of the CARBOEUROPE project.

Concerning the net radiation, the BSRN recommendations serve as a reference for the measurement data. Further investigations deal with the determination of the ground heat flux using different calculation approaches. To assess the quality of the results obtained, a sensitivity analysis study was conducted using the soil data measured during LITFASS-2003.