Evaporation and runoff from large land areas



An incomplete understanding of the processes of regional evaporation and runoff from the continents hinders future developments in our understanding of the global water cycle and of the Earth's climate. At present there is no clear consensus among geophysicists and biophysicists regarding the dynamic interaction of atmospheric, lithospheric, and biospheric processes in the determination of evaporation from large (characteristic length of 100 km and up) areas of continental surfaces. Observational data are scarce and uncertain, and disciplinary boundaries impede fully coupled theoretical analyses of the problem. As for runoff, large-scale measurements are available in the form of river discharges, so operational conceptual models can at least be calibrated and employed with some reliability.