The volume deals with the understanding the moist processes that determine the supply of water to the atmosphere and back to the surface. The observations of the distribution and variability of clouds and precipitation has emerged as a priority in Earth observational programs. Our ability to observe the amount of water vapor, and the properties of clouds and precipitation by satellites that presently orbit the Earth is unprecedented in the history of space-borne Earth observations. These new capabilities are now delivering important new insights on how water cycles through the Earth’s atmosphere and a firmer basis to predict how this water cycle evolves and thus how it may change with climate change.