The Hydrological Cycle and Climate

Water is a key part of the Earth system and interacts with climate through a variety of mechanisms. The chapter initially describes the effect of atmospheric moisture on the lapse rate and then discusses cloud formation and the main global reservoirs and fluxes, including precipitation, and discharge into the oceans. Atmospheric transport of water vapour, together with its relation to precipitation, is then discussed. It is shown that meridional transport can occur with a few very strong events, through atmospheric rivers. The difference between evaporation over the ocean and that over land is shown, with the help of data from Earth observation satellites, and the recycling of water is shown to depend very much on locality. Finally, the importance of frozen water on climate is described, using the recent decrease in Arctic sea ice, and the variability in ice sheet extent and consequent sea levels during the Last Glacial Maximum.