Fourth Study Conference on BALTEX Scala Cinema Gudhjem

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LITFASS-2003 - A Land Surface / Atmosphere Interaction Experiment:
Energy and Water Vapour Fluxes at Different Scales
Frank Beyrich 1 , Jens Bange 4 , Christian Bernhofer 6 , Henk A.R. de Bruin 8 , Thomas Foken 5 , Barbara
Hennemuth 2 , Sven Huneke 3 , Wim Kohsiek 7 , Jens-Peter Leps 1 , Horst Lohse 3 , Andreas Lüdi 9 ,
Matthias Mauder 5 , Wouter Meijninger 8 , Ronald Queck 6 and Peter Zittel 4
1 Meteorologisches Observatorium Lindenberg, Deutscher Wetterdienst (DWD), Am Observatorium 12, D-15848 Tauche /
OT Lindenberg, Germany, frank.beyrich@dwd.de
2 Max-Planck Institut für Meteorologie, Hamburg, Germany,
3 Institut für Küstenforschung - GKSS Forschungszentrum Geesthacht, Germany
4 Institut für Luft- und Raumfahrtsysteme, Technische Universität Braunschweig, Germany
5 Abteilung Mikrometeorologie, Universität Bayreuth, Germany
6 Institut für Meteorolgie und Hydrologie, Technische Universität Dresden, Germany
7 Koninklijk Nederlands Meteorologisch Instituut (KNMI), De Bilt, The Netherlands
8 Wageningen Universiteit, Leerstoelgroep Meteorologie en Luchtkwaliteit, Wageningen, The Netherlands
9 Institut für Angewandte Physik, Universität Bern, Switzerland
1. Introduction
Land surface - atmosphere interaction processes play an
important role in the energy and water cycle over a wide
magnitude of scales. Relevant process parameters are, i.a.,
net radiation, turbulent fluxes of energy and momentum,
evapotranspiration, and storage / transport of heat and water
in the soil. 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.
2. LITFASS-2003
The LITFASS-2003 experiment was organised within the
frame of the EVA_GRIPS project (Mengelkamp et al., this
issue) 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 have been determined from a combination of
ground-based in-situ and remote sensing instruments, and
airborne measurements. The measurement program
comprised, i.a.:
• 13 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),
• 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 measurement strategy is illustrated in Figure 1.
Figure 1. Measurement strategy during the
LITFASS-2003 experiment (red circles:
micrometeorological stations, red lines: LAS / MWS
paths, blue lines: Helipod grid flight pattern)
3. Results
Local energy and water vapour flux measurements over
the different types of land use showed significant
differences which were most pronounced between the
major land use classes (forest, low vegetation - farmland,
and water). This is illustrated in Figure 2. However,
significant differences have also been found between the
different types of agricultural farmland.
Pronounced flux differences between forest, agriculture,
and water have been measured over the whole experiment
period as can be seen from Figure 3. Turbulent heat
transport over the forest is always much larger than over
low vegetation. Evaporation over the forest became
comparably high only after rain events with a delay of
about one day (e.g., on May 21-22, June 07, June 10).