Energy and water vapour fluxes over a heterogeneous land surface: The LITFASS-2003 experiment

Land surface - atmosphere interaction processes play an important role in the energy and water cycle over a wide magnitude of scales. An adequate description of these processes in numerical weather prediction and climate models is fundamental for a reliable simulation of near surface weather and climate conditions. However, considerable deficits are still to be noticed concerning our understanding and ability to properly describe these processes consistently over a variety of scales ranging from the local patch to the regional landscape scale. To overcome these deficits, both experimental and modelling activities have to contribute.

The LITFASS-2003 experiment was organised within the frame of the EVA_GRIPS project (EVAporation at GRId / Pixel Scale) in order to provide a comprehensive data set on land surface and boundary layer processes over a heterogeneous landscape. It took place in the area around the Meteorological Observatory Lindenberg (MOL) of the German Meteorological Service (DWD) between May 19, and June 17, 2003. Energy and water vapour fluxes at different scales were determined from a combination of ground-based in-situ and remote sensing instruments, and airborne measurements. The measurement program comprised, i.a.: * thirteen micrometeorological stations operated over different surfaces representing the major land use types in the area (forest, water, and different types of agricultural farmland: grass, triticale, rape, maize), * three large aperture optical scintillometers (LAS) and a microwave scintillometer (MWS) set up along three different paths over distances of 3 to 10 km, * synchronised high-resolution (10 seconds sampling rate) measurements of water vapour and vertical velocity profiles by a Lidar-/RASS-combination, * more than 60 flight hours with a turbulence sonde carried by a Helicopter (the Helipod).

The paper will give an overview on the background and measurement strategy of the LITFASS-2003 experiment. First results will be discussed, these include the analysis and comparison of: * the local energy and water vapour fluxes measured over the different types of land use, * local and area-representative flux values obtained from the different measurement systems, * area-averaged fluxes as derived from ground-based ~, airborne ~, and satellite data against model results.

More detailed results from the LITFASS-2003 experiment will be presented in a small series of papers that are submitted to the conference in parallel.