The LITFASS project of DWD and the LITFASS-98 experiment: The project strategy and the experimental setup

The LITFASS project ('Lindenberg Inhomogeneous Terrain - Fluxes between Atmosphere and Surface: a Longterm Study') of the Deutscher Wetterdienst (DWD, German Meteorological Service) aims to develop and to test a strategy for the determination and parameterisation of the area-averaged turbulent fluxes of heat, momentum, and water vapour over a heterogeneous land surface. These fluxes will be representative for an area of about 10 * 10 km(2) (while the typical patch size is between 10(-1) to 10(0) km(2)) corresponding to the size of a grid cell in the present operational numerical weather prediction model of the DWD. LITFASS consists of three components: the development of a non-hydrostatic micro-alpha-scale model (the LITFASS local model - LLM) with a grid-size of about 100 * 100 m(2), experimental investigations of land surface - atmosphere exchange processes and boundary layer structure within a 20 * 20 km(2) area around the Meteorological Observatory Lindenberg, the assimilation of a data base as an interface between measurements and modelling activities. The overall project strategy was tested over a three-week period in June 1998 during the LITFASS-98 field experiment. This paper gives an overview on the LITFASS project, on the design and measurement program of the LITFASS-98 experiment, and on the weather conditions during the period of the experiment. Conclusions are formulated for the operational realisation of the LITFASS measurement concept and for future field experiments aimed at studying the land surface - atmosphere interaction in the Lindenberg area. Selected results from both experimental and modelling activities are presented in a series of companion papers completing this special issue of the journal.