remote sensing Review Satellite Remote Sensing of Precipitation and the Terrestrial Water Cycle in a Changing Climate Vincenzo Levizzani * and Elsa Cattani CNR-ISAC, via Gobetti 101, I-40129 Bologna, Italy;
[email protected] * Correspondence:
[email protected] Received: 13 September 2019; Accepted: 30 September 2019; Published: 2 October 2019 Abstract: The water cycle is the most essential supporting physical mechanism ensuring the existence of life on Earth. Its components encompass the atmosphere, land, and oceans. The cycle is composed of evaporation, evapotranspiration, sublimation, water vapor transport, condensation, precipitation, runoff, infiltration and percolation, groundwater flow, and plant uptake. For a correct closure of the global water cycle, observations are needed of all these processes with a global perspective. In particular, precipitation requires continuous monitoring, as it is the most important component of the cycle, especially under changing climatic conditions. Passive and active sensors on board meteorological and environmental satellites now make reasonably complete data available that allow better measurements of precipitation to be made from space, in order to improve our understanding of the cycle’s acceleration/deceleration under current and projected climate conditions. The article aims to draw an up-to-date picture of the current status of observations of precipitation from space, with an outlook to the near future of the satellite constellation, modeling applications, and water resource management. Keywords: water cycle; hydrological cycle; precipitation; water resources; climate change; satellite; remote sensing 1. Introduction The common description of the water cycle, or hydrological cycle, as consisting of evaporation, condensation, and precipitation is too simple to account for the high degree of complexity of the involved phenomena.