Preface: The LITFASS-2003 experiment

The success of weather forecasting and climate prediction essentially depends on our ability to understand and describe the energy and water cycles at various spatial and temporalscales.ThishasbeenrecognisedbytheWMOininitiatingtheGlobalEnergy and Water Cycle Project (GEWEX) as one of the major research activities within the framework of the World Climate Research Programme (WCRP). GEWEX covers measurements and modelling activities from the local up to the global scale and also provides an umbrella for a number of so-called continental-scale experiments (CSEs) that focus on the investigation of various aspects of the energy and water cycles in different geographic and climate regions of the earth. Recently, the efforts from the different CSEs have been brought together during a two-year Coordinated Enhanced Observation Period (CEOP) by combining long-term observations at a number of globally distributed reference sites, the analysis of global satellite data products and global climate model simulations in a number of the leading climate research centres of the world (Lawford et al. 2004). TheinternationalBalticSeaExperiment(BALTEX)astheEuropeancontribution to GEWEX is intended to describe and quantify the energy and water budget over the Baltic Sea Drainage Basin, an area of about 2 × 10 6 km 2 covering large parts of