A measure of the ability of a solution to behave as an acid, a compound that releases protons (H+) to the water in which it is dissolved. Compare alkalinity.
albedo
The amount of solar radiation reflected by a surface, usually expressed as a percent of the incident solar radiation.
alkalinity
A measure of the ability of a solution to behave as a base, a compound that takes up protons (H+) or releases hydroxide ions (OH–). Compare acidity.
anoxic
Having a low oxygen concentration.
atmospheric pressure
The pressure the exerted on a surface due to the mass of the atmosphere above it.
climate
The long-term description of weather, based on averages and variation measured over decades. Compare weather.
conduction
The transfer of sensible heat through the exchange of kinetic energy by molecules in direct contact with one another. Compare convection.
continental climate
The climate typical of terrestrial areas in the middle of large continental land masses at high latitudes, characterized by high variation in seasonal temperatures. Compare maritime climate.
convection
The transfer of sensible heat through the exchange of air and water molecules as they move from one area to another. Compare conduction.
Coriolis effect
The influence of the frictional forces associated with the spinning of Earth on its axis on wind and ocean current direction.
El Niño Southern Oscillation (ENSO)
A climatic oscillation in the Pacific Ocean causing widespread climate variation and changes in upwelling currents, characterized by a switch in the positions of high-pressure and low-pressure systems over the equatorial Pacific, leading to a weakening of the easterly trade winds that normally push warm water toward Southeast Asia. See also La Niña.
epilimnion
The warm surface layer of water in a lake, lying above the thermocline, that forms during the summer in some lakes of temperate and polar regions. Compare hypolimnion.
evapotranspiration
The sum of water loss through evaporation and transpiration .
Ferrell cell
A large-scale, three-dimensional pattern of atmospheric circulation in each hemisphere, located at mid-latitudes between the Hadley and polar cells.
greenhouse gases
Atmospheric gases that absorb and reradiate the infrared radiation emitted by Earth’s surface, including water vapor (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).
Hadley cell
A large-scale, three-dimensional pattern of atmospheric circulation in each hemisphere in which air is uplifted at the equator and subsides at about 30° N and S.
heat capacity
The amount of energy required to raise the temperature of a substance.
hypolimnion
The densest, coldest water layer in a lake, lying below the thermocline. Compare epilimnion.
Intertropical Convergence Zone (ITCZ)
The zone of maximum solar radiation, atmospheric uplift, and precipitation within the tropical zone.
La Niña
A stage of the El Niño Southern Oscillation consisting of a stronger-than-average phase of the normal climatic pattern, with high atmospheric pressure off the coast of South America and low pressure in the western Pacific.
lapse rate
The rate at which atmospheric temperature decreases with increasing distance from the ground.
latent heat flux
Heat transfer associated with the phase change of water, such as evaporation, sublimation, or condensation.
maritime climate
The climate typical of coastal terrestrial regions that are influenced by an adjacent ocean, characterized by low daily and seasonal variation in temperature. Compare continental climate.
Milankovitch cycles
Cycles of regular change over thousands of years in the shape of Earth’s orbit, in the angle of tilt of its axis, and in its orientation toward other celestial bodies that change the intensity of solar radiation primarily at high latitudes.
North Atlantic Oscillation
An oscillation in atmospheric pressures and ocean currents in the North Atlantic Ocean that affects climatic variation in Europe, in northern Asia, and on the eastern coast of North America.
Pacific Decadal Oscillation (PDO)
A long-term oscillation in sea surface temperatures and atmospheric pressures in the North Pacific Ocean that affects climates primarily in northwestern North America.
polar cell
A large-scale, three-dimensional pattern of atmospheric circulation in which air subsides at the poles and moves toward the equator when it reaches Earth’s surface, and is replaced by air moving through the upper atmosphere from lower latitudes.
polar zone
The major climatic zone above 60° N and S.
radiatively active gases
See greenhouse gases.
rain-shadow effect
The effect a mountain range has on climate by forcing moving air upward, causing it to cool and release precipitation on the windward slopes, resulting in lower levels of precipitation and soil moisture on the leeward slope.
salinity
The concentration of dissolved salts in water.
salinization
A process by which high rates of evapotranspiration in arid regions result in a progressive buildup of salts at the soil surface.
sensible heat flux
The transfer of heat through the exchange of energy by conduction or convection.
stratification
The layering of water in oceans and lakes due to differences in water density and temperature with depth.
subsidence
In meteorology, a sinking (downward) motion in the atmosphere, usually over a broad area, leading to the development of a high pressure cell. Compare uplift.
temperate zone
The major climatic zone between 30° and 60° N and S.
thermocline
The zone of rapid temperature change in a lake beneath the epilimnion and above the hypolimnion.
transpiration
The evaporation of water from the inside of a plant, typically through stomatal pores.
tropical zone
The major climatic zone between 25° N and S, encompassing the equator.
turnover
The mixing of the entire water column in a stratified lake when all the layers of water reach the same temperature and density.
uplift
(meteorology) The rising of warm, less dense air in the atmospheredue to surface heating. Compare subsidence.
upwelling
The rising of deep ocean waters to the surface where prevailing wind patterns cause surface waters to flow away from a coast.
variability
The range of abiotic conditions in an environment.
weather
The current temperature, humidity, precipitation, wind, and cloudiness. Compare climate.
