Earth sciences

Water scarcity

Water scarcity, also known as water shortage, is the condition in which demand for freshwater exceeds available supply in an area, affecting consumption, irrigation, and industry.

Water scarcity in India

Water scarcity in India, also called water shortages in India, is the shortfall of freshwater against demand, leaving roughly 600 million people facing water stress.

Water table

The water table, or groundwater level, is the surface in an unconfined aquifer where groundwater pressure equals atmospheric pressure, marking the top of the saturated zone.

Water vapor

Water vapor, also called gaseous water, is water in its gas phase. It is Earth's most abundant greenhouse gas, amplifying climate change through a positive feedback loop.

Water vapor feedback

Water vapor feedback is the amplification of global warming that occurs because a warmer atmosphere holds more water vapor, itself a greenhouse gas that traps additional heat.

WaterGAP

WaterGAP (Water – Global Assessment and Prognosis) is a global hydrological model developed at the University of Kassel since 1996 to assess water resources and stress.

Waterspout

A waterspout is a whirling column of air and water mist over a body of water, coming in two types: tornadic waterspouts and more common fair weather waterspouts.

Wave diffraction

Wave diffraction is the lateral transfer of wave energy along a wave crest into the sheltered region behind an obstacle such as a breakwater or island.

Wave Glider

The Wave Glider is an autonomous, uncrewed surface vehicle made by Liquid Robotics, a Boeing subsidiary, that converts ocean wave energy into thrust and runs up to 12 months at sea.

Wave radar is a radar-based remote sensing method that measures the directional ocean wave spectrum without placing an instrument in the water, using X-band nautical radar or high-frequency ground-wave radar.

Wave runup

Wave runup is the maximum vertical elevation reached by wave uprush above still-water level on a beach or coastal structure, made up of wave setup and swash.

Wave setup

Wave setup is the rise in mean sea level at the coast caused by breaking waves, adding to tide and storm surge inside the surf zone.

Wave spectrum

A wave spectrum is the statistical distribution of ocean wave energy across wave frequencies and directions, distinguishing wind waves from swell and underpinning operational wave forecasting models.

Wavefield reconstruction

Wavefield reconstruction is a geophysical method that recovers a complete seismic or acoustic wavefield from sparse, irregularly sampled data, a prerequisite for full waveform inversion and least-squares migration.

Wavefield separation

Wavefield separation is a signal-processing method in seismology that decomposes recorded seismic data into components such as upgoing and downgoing waves or P- and S-waves, feeding migration and full-waveform inversion.

Waveform tomography

Waveform tomography, known as full waveform inversion (FWI), is an iterative seismic method that estimates subsurface velocity structure by minimizing the difference between recorded and synthetic waveforms.

WAVEWATCH III

WAVEWATCH III is a third-generation spectral wind-wave model developed at NOAA/NCEP, the National Weather Service's operational global wave forecast model since 2000, run as GFS-Wave coupled to the Global Forecast System.

WEAP

WEAP (Water Evaluation and Adaptation Planning, originally Water Evaluation and Planning) is a software tool for integrated water resources planning developed by the Stockholm Environment Institute, used in nearly 200 countries.

Weather

Weather is the state of the atmosphere at a place over the short term, minutes to days, measured through temperature, precipitation, wind, and cloudiness, distinct from climate.

Weather balloon

A weather balloon, or sounding balloon, is a balloon inflated with hydrogen or helium that carries a radiosonde transmitting pressure, temperature, and humidity measurements as it rises.

Weather buoy

A weather buoy is a moored or drifting floating platform that automatically measures and transmits ocean weather data such as wind, air and sea temperature, pressure, and waves.

Weather forecasting

Weather forecasting, also called meteorological forecasting, is the application of science and technology to predict the atmosphere at a future time and location, chiefly through numerical weather prediction.

Weather front

A weather front is a boundary between air masses of different temperature or moisture, along which mid-latitude cloud and rain concentrate. Cold, warm, occluded, and stationary fronts are the main types.

Weather map

A weather map, also called a weather chart, uses symbols, lines, and colors to show atmospheric conditions such as pressure, fronts, and temperature over a region.

Weather modification

Weather modification, also called weather control, is the deliberate alteration of weather, chiefly by seeding clouds with substances like silver iodide to increase rain or suppress hail.

Weather of 2025

The weather of 2025 was the second or third warmest year on record at about 1.44 °C above pre-industrial averages, and the warmest without an El Niño.

Weather of 2026

The weather of 2026 was shaped by a strong El Niño and record global heat, bringing a record-quiet Atlantic hurricane season and a record March heat wave in the western United States.

Weather presenting

Weather presenting is the broadcast craft of delivering weather information on radio or television, combining newscaster delivery skills with interpretation of meteorological data, a field credentialed by the American Meteorological Society.

Weather Research and Forecasting Model

The Weather Research and Forecasting (WRF) Model is an open-source numerical weather prediction system, first released in 2000, that simulates wind, temperature, and precipitation over regional domains for forecasting and research.