Waldstein, 12.05. - 18.07.2003

WALDATEM-2003

From 05/2003 to 12/2004

Experiment manager: Thomas Foken
Staff: Christoph Thomas, Johannes Ruppert, Theresa Bertolini, Johannes Lüers, Johannes Olesch, Jens-Christopher Mayer, Joel Schröter, Gennady N. Panin

Field campaign WALDATEM at the site tower Weidenbrunnen/ Waldstein: The field campaign is carried out in the framework of the BITOEK-research program and aims on the intensive investigation of coherent structures and carbon fluxes within and above a tall spruce forest. The name WALDATEM was chosen from the analysing system used in the campaign: WALD= WaveLet Detection and ATEM= Atmospheric TurbulencE Measurements. Coherent Structures are well-organized low-frequent eddies with their spatial and temporal scales being different from well-known turbulence. The eddy-covariance-technique used for the determination of the overall flux does not account for their contribution to the flux or gives erroneous results. Detection and analysis of the coherent structures is performed using the software WALDSCHRAT (WAveLet Detection Software for CoHerent Ramp paTterns) developed at the Department of Micrometeorology/ Bitoek, University of Bayreuth. Its implemented algorithms are based on the wavelet transform and yield results about both individual events and statistical properties. The input data are obtained by a vertical profile of sonic anemometers covering all parts of the forest up to the lower part of the roughness sublayer. The sonics are installed at 6 different heights and operated at a sampling frequency not smaller than 10 Hz, while 4 heights are additionally equipped with fast CO2 and/ or H2O analysers for assessing the carbon dioxide and water vapour budgets. The vertical profile is continued up to a height of several hundreds of meters above ground by using acoustic and radar remote sensing (SODAR-RASS). The results are expected to enhance the accuracy and reliability of ecosystem flux measurements and allow deeper insight into the dynamics of the generation of coherent structures. Detailed information about source and sink terms of the carbon budget are assessed through measurements of 13C isotope fluxes. For this purpose, Relaxed Eddy Accumulation (REA) technique is here being applied. The air samples are taken at the top level of the sonic profile ~ 13m above the canopy top at a height of 33m above ground. The applied REA system takes "whole air" samples, which are temporally stored in reservoirs before being filled into glass flasks. The air samples are subsequently analysed in the isotope laboratory of the Max-Planck-Institute of Jena with high precision. Diurnal variations of the mean carbon dioxide concentration within the spruce forest are obtained through combined CO2-/ 13C-profile measurements. Despite its goal studying local processes within the canopy, it is used to assess the vertical advection terms in the CO2 budget. Both applied systems are controlled by the software ATEM and ATEM_profile developed at the Department of Micrometeorology/ Bitoek, University of Bayreuth. Three small towers placed at a distance of 50m from the main tower give additional information about the advective flow in the subcanopy space, while the CO2-analysing system "Hydra" developed at the National Center for Atmospheric Research in Boulder/ USA will be used for determination of the horizontal advective terms. Special interest is paid to cold drainage flow along the smooth slope during night conditions.

List of publications of this Experiment

Thomas, C; Foken, T: Organised motion in a tall spruce canopy: temporal scales, structure spacing and terrain effects, Boundary-Layer Meteorology, 122, 123-147 (2007), doi:10.1007/s10546-006-9087-z -- Details

Thomas, C; Foken, T: Flux contribution of coherent structures and its implications for the exchange of energy and matter in a tall spruce canopy, Boundary-Layer Meteorology, 123, 317-337 (2007), doi:10.1007/s10546-006-9144-7 -- Details

Ruppert, J; Thomas, C; Foken, T: Scalar similarity for relaxed Eddy accumulation methods , Boundary-Layer Meteorology, 120, 39-63 (2006) -- Details

Göckede, M; Thomas, C; Markkanen, T; Ruppert, J; Mauder, M; Foken, T: On the sensitivity of Lagrangian stochastic footprint modeling to within canopy flow statistics derived from wavelet analysis, Report Series in Aerosol Science, 79, 247-249 (2006)

Ruppert, J; Mauder, M; Thomas, C; Lüers, J: Innovative gap-filling strategy for annual sums of CO2 net ecosystem exchange, Agricultural and Forest Meteorology, 138, 5-18 (2006), doi:10.1016/j.agrformet.2006.03.003 -- Details

Thomas, C; Mayer, JC; Meixner, FX; Foken, T: Analysis of the low-frequency turbulence above tall vegetation using a Doppler sodar, Boundary-Layer Meteorology, 119, 563-587 (2006), doi:10.1007/s10546-005-9038-0 -- Details

Thomas, C; Foken, T: Detection of long-term coherent exchange over spruce forest, Theoretical and Applied Climatology, 80, 91-104 (2005) [Link] -- Details

Ruppert, J: Woher kommt das CO2 in Universität Bayreuth: Spektrum, Nr. 3, 34-35 (2004)

Related links:

• Diploma Thesis: Characterisation of the Atmospheric Boundary-Layer in a Complex Terrain using SODAR-RASS
• Field of research: CO2: Carbon dioxide fluxes
• PhD Thesis: Detection and analysis of coherent structures within and above tall-vegetated canopies
• Project: BITÖK-A3: Klimatologie und Deposition von Luftschadstoffen im Fichtelgebirge
• Project: BITÖK-A6: Einflüsse kohärenter Strukturen auf den Energie- und Stoffaustausch in hohen Beständen
• Project: BITÖK-A7: Messung turbulenter Flüsse von Kohlendioxid und stabilem Kohlenstoffisotop 13 über Pflanzenbeständen mit Hilfe der Relaxed Eddy Accumulation-Methode