Water and climate are tightly linked: Water vapor is by far the most important greenhouse gas; conversely, diachronic changes to climate impact hydrology. While hydrological change is influenced by many factors in addition to climate, and climate includes processes other than hydrological, nonetheless it would seem that one has to study water cycle and climate, the two phenomena, together, particularly if one wants to characterize future hydrological conditions -- e.g. water availability or flood hazards -- or understand future climate -- e.g. evaporation off land surfaces. However, the two corresponding scientific disciplines employ very different tools and methods. Although a number of sessions focus on assessing impacts of climate and hydrological change, this session seeks papers exploring the more fundamental physical interface between climate and hydrology: What can hydrology offer to climate science, and vice versa? Papers that explore how hydrological and climatological data can be employed to improve our understanding of the physical processes associated with climate, to calibrate models, to improve forecasts and predictions, and to estimate corresponding uncertainties, are particularly sought.