Glossary main content.


air current

A moving stream of air.

air pressure

See: Atmospheric pressure.


A simple photosynthetic plant that lives in aquatic environments.

algal bloom

Occurs when algae grow very fast to accumulate into dense patches near the wateràs surface. ìHarmful algal bloomsî contain toxins or cause negative impacts.

atmospheric pressure

Pressure exerted by the mass of the atmosphere above a point on, or above, a planet as a result of gravitational attraction between the planet and its atmosphere. Low pressure indicates pressure that is below average, while high pressure indicates pressure that is above average.


An instrument for measuring atmospheric pressure.


Average weather conditions of a region, including temperature, precipitation, and winds.


Information, often in the form of measurements or observations, which can be analyzed.datasetA collection of data over time.


On the time scale of decades, or tens of years.


The study of past climates by analyzing the annual rings of trees.


A community of interacting organisms and their physical environment.

El Niño

A large-scale ocean-atmosphere climate phenomenon linked to a periodic warming in sea surface temperatures across the central and east-central equatorial Pacific. El Niño represents the warm phase of the El Niño/Southern Oscillation (ENSO) cycle.

global warming

An increase in Earth's average temperature.

greenhouse gases

Gases, primarily water vapor, carbon dioxide, ozone, nitrous oxide, and methane, which increase global temperatures by absorbing outgoing radiation emitted by the Earth's surface. Also called GHGs.

Gulf Stream

A warm ocean current of the northern Atlantic Ocean off eastern North America. It originates in the Gulf of Mexico, then flows northward along the southeast coast of the US. North of Cape Hatteras, NC, the Gulf Stream veers northeastward into the Atlantic Ocean.

Jet Stream

A high-speed air current in the upper atmosphere.


The areas between about 30° and 55° latitude, in either the Northern or Southern hemisphere.

North Atlantic Oscillation

A seesaw of atmospheric mass between the Icelandic low pressure system and the Azores high pressure system.

North Atlantic Oscillation index

The difference of normalized sea level pressure between the Azores high and the Icelandic low for a four-month winter season (December-March).


A chemically active gas, the molecule of which consists of three oxygen atoms (O 3). In the stratosphere, ozone acts as a protective barrier for Earth's surface by absorbing much of the potentially damaging ultraviolet radiation that comes from the Sun. In the troposphere, ozone acts as a harmful pollutant and is one of the primary greenhouse gases.


The amount of dissolved salts in water.


The layer of the atmosphere above the troposphere. The stratosphere extends from approximately ten to fifty kilometers above Earth's surface.


The lowest layer of Earth's atmosphere in contact with Earth's surface. Most weather occurs within the troposphere. The troposphere extends from Earth's surface to elevations of approximately 10-15 kilometers.