From 1995 till 2001, the German Meteorological Service (DWD) has performed a research project (LITFASS='Lindenberg Inhomogeneous Terrain - Fluxes between Atmosphere and Surface: a Long-term Study') in order to develop and to test a strategy for the determination of the area-averaged turbulent fluxes of heat, momentum, and water vapour over a heterogeneous landscape. The fluxes shall be representative for a horizontal scale of about 10 km (while the typical patch scale is between 10^2 to 10^3 m) corresponding to the size of a grid cell in the present operational numerical weather prediction model of the DWD. The overall project strategy had been successfully tested over a four weeks period in May / June 1998 during the LITFASS-98 field experiment, results from this experiment were presented at the 14th Symposium on Boundary Layer and Turbulence. Over the last two years, the LITFASS measurement program was qualified for continuous long-term operation.

The paper will review the current status of the LITFASS field program, and we will present selected results from the operational measurements performed in 2000 and 2001. These include: - the variability of meteorological forcing (radiation budget, rain, wind and temperature profiles) across the area, - the variability of turbulent fluxes depending on different surface characteristics and on the meteorological forcing, - the estimation of area-averaged sensible heat fluxes from the operation of a large-aperture scintillometer. In addition, first modelling results for some case studies will be discussed. Finally, an outlook will be given towards a second field experiment (LITFASS-2003) aimed at the determination of area-averaged evaporation at grid-/pixel scale.