The Baltic Sea Experiment (BALTEX): A European contribution to the investigation of the energy and water cycle over a large drainage basin

The Baltic Sea Experiment (BALTEX) is one of the five continental-scale exp eriments of the Global Energy and Water Cycle Experiment (GEWEX). More than 50 research groups from 14 European countries are participating in this pr oject to measure and model the energy and water cycle over the large draina ge basin of the Baltic Sea in northern Europe. BALTEX aims to provide a bet ter understanding of the processes of the climate system and to improve and to validate the water cycle in regional numerical models for weather forec asting and climate studies. A major effort is undertaken to couple interact ively the atmosphere with the vegetated continental surfaces and the Baltic Sea including its sea ice. The intensive observational and modeling phase BRIDGE, which is a contribution to the Coordinated Enhanced Observing Perio d of GEWEX, will provide enhanced datasets for the period October 1999-Febr uary 2002 to validate numerical models and satellite products. Major achiev ements have been obtained in an improved understanding of related exchange processes. For the first time an interactive atmosphere-ocean-land surface model for the Baltic Sea was tested. This paper reports on major activities and some results.