Key Environmental and Atmospheric Definitions

Glossary of Atmospheric and Environmental Terms

Albedo

Solar energy reflected back to space by clouds and airborne dust.

Anticyclone

Areas of high pressure caused by descending air masses.

Inversion

A zone of the troposphere where the temperature increases with height due to a disturbance of the vertical temperature gradient.

Urban Heat Island (UHI)

A phenomenon where urban warm air rises and cools down on the outskirts of the city, creating a local cyclical movement that retains pollution and maintains a temperature a few degrees higher than that of the surrounding areas.

Low-Pressure System (Cyclone)

Areas of low pressure caused by rising air masses.

Climate

A set of atmospheric conditions that characterize a region.

Greenhouse Effect

A process by which the lower atmosphere warms following the absorption of infrared rays emitted by the surface, which then emits longwave radiation, part toward space and part back toward the surface.

Glaciation

A long period during which the Earth's climate temperature lowers, resulting in an expansion of continental ice from the polar ice caps and glaciers.

Stratospheric Ozone

Ozone found between 15 and 35 km altitude, forming the ozone layer.

Troposphere

The lowest layer of the atmosphere, extending to an average of 12 km, where weather events that determine the climate occur.

Acidic Water

Water that, when mixed with hydrogen ions, results in a pH below 5.6.

Pollution

Any substance or form of energy that can cause a change in an ecosystem, the physical environment, or a living organism.

Primary Pollutant

A pollutant that reaches the atmosphere directly from emission sources.

Secondary Pollutant

A pollutant formed by the alteration of primary pollutants due to solar radiation.

Acid Rain

Rainwater that forms when hydrogen ions lower the pH to below 5.6. It falls as precipitation in areas remote from the emission source and is often characterized as being very clean.

Photochemical Smog

A reddish-brown mixture that forms when nitrogen oxides react with atmospheric hydrocarbons, excited by solar radiation.

Biofuel

Fuels formed from organic matter.

Fossil Fuels

Geological, nonrenewable energy resources.

Natural Hazard

The danger of a disaster occurring due to natural causes.