Hydrology is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydrologist. Hydrologists are scientists studying earth or environmental science, civil or environmental engineering, and physical geography. Using various analytical methods and scientific techniques, they collect and analyze data to help solve water related problems such as environmental preservation, natural disasters, and water management.
A sudden stratospheric warming (SSW) is an event in which polar stratospheric temperatures rise by several tens of kelvins over the course of a few days. The warming is preceded by a slowing then reversal of the westerly winds in the stratospheric polar vortex, commonly measured at 60 ° latitude at the 10 hPa level. SSWs occur about six times per decade in the northern hemisphere (NH), and about once every 20-30 years in the southern hemisphere (SH). In the SH, SSW accompanied by a reversal of the vortex westerly was observed once during the period 1979–2024; this was in September 2002. Stratospheric warming in September 2019 was comparable to or even greater than that of 2002, but the wind reversal did not occur.
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls from clouds due to gravitational pull. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and "precipitates" or falls. Thus, fog and mist are not precipitation; their water vapor does not condense sufficiently to precipitate, so fog and mist do not fall. Two processes, possibly acting together, can lead to air becoming saturated with water vapor: cooling the air or adding water vapor to the air. Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers.
Clouds and the Earth's Radiant Energy System (CERES) is an on-going NASA climatological experiment from Earth orbit. The CERES are scientific satellite instruments, part of the NASA's Earth Observing System (EOS), designed to measure both solar-reflected and Earth-emitted radiation from the top of the atmosphere (TOA) to the Earth's surface. Cloud properties are determined using simultaneous measurements by other EOS instruments such as the Moderate Resolution Imaging Spectroradiometer (MODIS). Results from the CERES and other NASA missions, such as the Earth Radiation Budget Experiment (ERBE), could enable nearer to real-time tracking of Earth's energy imbalance (EEI) and better understanding of the role of clouds in global climate change.
In hydrology, moisture recycling or precipitation recycling refer to the process by which a portion of the precipitated water that evapotranspired from a given area contributes to the precipitation over the same area. Moisture recycling is thus a component of the hydrologic cycle. The ratio of the locally derived precipitation to total precipitation is known as the recycling ratio, ρ:
The Indian Ocean Dipole (IOD), also known as the Indian Niño, is an irregular oscillation of sea surface temperatures in which the western Indian Ocean becomes alternately warmer and then colder than the eastern part of the ocean.
In climate science, a biosphere model, is used to model the biosphere of Earth, and can be coupled with atmospheric general circulation models (GCMs) for modelling the entire climate system. It has been suggested that terrestrial biosphere models (TBMs) are a more inclusive term than land surface models (LSMs). The representation of roots in TBMs, however, remains relatively crude. Particularly, the dynamic functions of roots and phylogenetic basis of water uptake remain largely absent in TBMs.
A hydrologic model is a simplification of a real-world system that aids in understanding, predicting, and managing water resources. Both the flow and quality of water are commonly studied using hydrologic models.
The Global Energy and Water Exchanges Project is an international research project and a core project of the World Climate Research Programme (WCRP).
Soil Moisture Active Passive (SMAP) is a NASA environmental monitoring satellite that measures soil moisture across the planet. It is designed to collect a global 'snapshot' of soil moisture every 2 to 3 days. With this frequency, changes from specific storms can be measured while also assessing impacts across seasons of the year. SMAP was launched on 31 January 2015. It was one of the first Earth observation satellites developed by NASA in response to the National Research Council's Decadal Survey.
An atmospheric river (AR) is a narrow corridor or filament of concentrated moisture in the atmosphere. Other names for this phenomenon are tropical plume, tropical connection, moisture plume, water vapor surge, and cloud band.
The Cyclone Global Navigation Satellite System (CYGNSS) is a space-based system developed by the University of Michigan and Southwest Research Institute with the aim of improving hurricane forecasting by better understanding the interactions between the sea and the air near the core of a storm.
PERSIANN, "Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks", is a satellite-based precipitation retrieval algorithm that provides near real-time rainfall information. The algorithm uses infrared (IR) satellite data from global geosynchronous satellites as the primary source of precipitation information. Precipitation from IR images is based on statistical relationship between cloud top temperature and precipitation rates. The IR-based precipitation estimates are then calibrated using satellite microwave data available from low Earth orbit satellites. The calibration technique relies on an adaptive training algorithm that updates the retrieval parameters when microwave observations become available.
In meteorology, a precipitationshed is the upwind ocean and land surface that contributes evaporation to a given, downwind location's precipitation. The concept has been described as an "atmospheric watershed". The concept itself rests on a broad foundation of scholarly work examining the evaporative sources of rainfall. Since its formal definition, the precipitationshed has become an element in water security studies, examinations of sustainability, and mentioned as a potentially useful tool for examining vulnerability of rainfall dependent ecosystems.
The brown ocean effect is an observed weather phenomenon involving some tropical cyclones after landfall. Normally, hurricanes and tropical storms lose strength when they make landfall, but when the brown ocean effect is in play, tropical cyclones maintain strength or even intensify over land surfaces. Australia is the most conducive environment for this effect, where such storm systems are called agukabams.
Michael Ghil is an American and European mathematician and physicist, focusing on the climate sciences and their interdisciplinary aspects. He is a founder of theoretical climate dynamics, as well as of advanced data assimilation methodology. He has systematically applied dynamical systems theory to planetary-scale flows, both atmospheric and oceanic. Ghil has used these methods to proceed from simple flows with high temporal regularity and spatial symmetry to the observed flows, with their complex behavior in space and time. His studies of climate variability on many time scales have used a full hierarchy of models, from the simplest ‘toy’ models all the way to atmospheric, oceanic and coupled general circulation models. Recently, Ghil has also worked on modeling and data analysis in population dynamics, macroeconomics, and the climate–economy–biosphere system.
Elfatih Ali Babiker Eltahir is a Sudanese -American Professor of Civil and Environmental Engineering, H.M. King Bhumibol Professor of Hydrology and Climate, and Director of the MIT-UM6P Research Program at the Massachusetts Institute of Technology.
In atmospheric science, a cold pool (CP) is a cold pocket of dense air that forms when rain evaporates during intense precipitation e.g. underneath a thunderstorm cloud or a precipitating shallow cloud. Typically, cold pools spread at 10 m/s and last 2–3 hours. Cold pools are ubiquitous both over land and ocean.
The effects of climate change on the water cycle are profound and have been described as an intensification or a strengthening of the water cycle. This effect has been observed since at least 1980. One example is when heavy rain events become even stronger. The effects of climate change on the water cycle have important negative effects on the availability of freshwater resources, as well as other water reservoirs such as oceans, ice sheets, the atmosphere and soil moisture. The water cycle is essential to life on Earth and plays a large role in the global climate system and ocean circulation. The warming of our planet is expected to be accompanied by changes in the water cycle for various reasons. For example, a warmer atmosphere can contain more water vapor which has effects on evaporation and rainfall.
Martha Carol Anderson is research scientist with the United States Department of Agriculture. She is known for her work in using satellite imagery to track droughts and their impact on crops. In 2022, she was elected a fellow of the American Geophysical Union. In 2024, she was elected a fellow of the National Academy of Engineering.
