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Atmosphere
The atmosphere is the layer of gases surrounding Earth, held by gravity, supplying breathable air, blocking ultraviolet radiation, and warming the surface through the greenhouse effect.
Atmosphere of Earth
The atmosphere of Earth is the layer of gases retained by gravity, made mostly of nitrogen and oxygen, that supplies air, drives weather, and blocks harmful radiation.
Atmospheric absorption
Atmospheric absorption is the process by which atmospheric gases, clouds, and particles take up electromagnetic radiation as heat; water vapor contributes about 50% of infrared absorption, clouds 25%, and CO2 20%.
Atmospheric chemistry
Atmospheric chemistry is the branch of atmospheric science that studies the chemical composition of Earth's atmosphere and the reactions that produce and remove its gases and particles.
Atmospheric circulation
Atmospheric circulation, or the three-cell model, is the large-scale motion of Earth's atmosphere carrying heat, moisture, and momentum from the tropics poleward through Hadley, Ferrel, and polar cells.
Atmospheric CO2 concentration
Atmospheric CO2 concentration is the abundance of carbon dioxide in Earth's atmosphere, measured in parts per million and up from 280 ppm before the Industrial Revolution to 423 ppm in 2024.
Atmospheric correction
Atmospheric correction is the remote sensing processing step that removes atmospheric scattering and absorption from satellite or airborne sensor measurements, recovering surface reflectance over land and water-leaving radiance over ocean.
Atmospheric dispersion model
An atmospheric dispersion model is a mathematical model simulating how pollutants released from emission sources are transported, dispersed, and deposited, producing concentration estimates used in air quality regulation.
Atmospheric dispersion modeling
Atmospheric dispersion modeling uses simulation methods, most commonly Gaussian plume models like AERMOD, to predict how airborne pollutants spread from sources such as stacks and spills.
Atmospheric diving suit
An atmospheric diving suit, or ADS, is a tethered one-person submersible shaped like a suit of armor, keeping the operator at surface pressure to avoid decompression sickness.
Atmospheric escape
Atmospheric escape is the loss of a planetary atmosphere to space by gas particles whose energy exceeds the planet's gravity, shaping how planets evolve over time.
Atmospheric river
An atmospheric river is a long, narrow corridor of water vapor that carries most moisture outside the tropics, bringing heavy rain or snow where it landfalls.
Atmospheric tide
An atmospheric tide is a planetary-scale oscillation of the atmosphere whose period is a fraction of a solar or lunar day, driven by solar heating and lunar gravity.
Attenuation tomography
Attenuation tomography is a geophysical imaging method that maps seismic wave attenuation in the Earth's interior, imaging the quality factor Q from recorded amplitudes and spectra of seismic waves.
Attribution analysis (climate science)
Attribution analysis in climate science is a statistical method that quantifies how much human activities and natural factors each contribute to observed climate changes and extreme events.
Attribution of recent climate change
Attribution of recent climate change, also called man-made global warming attribution, is the science of measuring how much observed warming is caused by human activities.
Atuel, Caldera del
Caldera del Atuel is a 30 x 45 km volcanic caldera complex in southern Mendoza, Argentina, near the Chilean border, with 15 dacitic lava domes and 25 young andesitic stratovolcanoes and cinder cones on its floor; no Holocene eruptions are known.
Auckland volcanic field
The Auckland volcanic field (Ngā Maunga a Mataaho) is a basaltic volcanic field of about 53 centers beneath Auckland, New Zealand, first erupting roughly 193,000 years ago.
Aufeis
Aufeis, also called icing or naled, is layered ice formed when groundwater overflows onto frozen ground or river ice and freezes, sometimes several meters thick, as in Siberia.
Augite
Augite is the most common pyroxene mineral, a dark green to black rock-forming silicate, and a principal constituent of mafic igneous rocks like basalt and gabbro, named from the Greek for luster.
August 2020 Midwest derecho
The August 2020 Midwest derecho was a severe thunderstorm complex that crossed the central United States on August 10, 2020, causing $11 billion in damage, the costliest thunderstorm event in modern U.S. history.
Auquihuato, Cerro
Cerro Auquihuato (Auquihuato volcano) is an andesitic cinder cone in Ayacucho, Peru, Central Andean Volcanic Arc, ~5,000 m high, ~30 km NE of Sara Sara, undated Holocene lava flow, InSAR uplift, IGP-monitored.
Auroral electrojet
The auroral electrojet is a band of intense ionospheric electric current at auroral latitudes, tracked by the AE geomagnetic index introduced by Davis and Sugiura in 1966.
Auroral oval
The auroral oval is the roughly elliptical band of aurora around each geomagnetic pole, fixed toward the Sun and identified by Alexander Feldstein in 1963.
Australian Hydrographic Service
The Australian Hydrographic Service, also known as the Royal Australian Navy Hydrographic Service, is the Australian Department of Defence agency responsible for surveying and charting Australian waters, formed in 1920.
Australian monsoon
The Australian monsoon is the seasonal reversal of winds over northern Australia that each summer brings moist air and heavy rain, delivering most of the region's annual rainfall from November to April.
Australian plate
The Australian plate is a major tectonic plate carrying Australia and nearby crust, moving northeast at about 7 cm per year, the fastest continental land mass on Earth.
Automatic weather station
An automatic weather station is a set of meteorological instruments that measures surface weather variables and transmits the data without an observer on site, serving remote locations.
Autonomous underwater vehicle
An autonomous underwater vehicle (AUV), also called an autonomous undersea vehicle or autonomous submarine, is an uncrewed, untethered underwater robot that executes pre-programmed missions without operator control.
Autoregressive rollout forecasting
Autoregressive rollout forecasting is the method machine-learning weather models use to extend forecasts: they predict a short step ahead, feed it back in, and repeat.