Unit 8

Troposphere

Layer of the atmosphere closest to Earth’s surface, where most of the mass of atmosphere is found and in which most weather takes place.

Stratosphere

Layer of Earth’s atmosphere located above the tropopause, primarily made up of concentrated ozone.

Mesosphere

Layer of Earth’s atmosphere above the stratopause.

Thermosphere

Layer of Earth’s atmosphere located above the mesopause, where oxygen atoms absorb solar radiation causing the temperature to increase.

Exosphere

Outermost layer of Earth’s atmosphere, located above the thermosphere, with no clear boundary at the top, transitional region between Earth’s atmosphere and outer space.

Radiation

The transfer of thermal energy by electromagnetic waves, specifically from the Sun to the Earth.

Conduction

The transfer of thermal energy between objects in contact through collisions between particles.

Convection

The transfer of thermal energy by the movement of heated material from one place to another.

Greenhouse effect

Natural process where certain atmospheric gases absorb heat radiating off the planet’s surface, preventing loss of heat to space.

Temperature inversion

Increase in temperature with height in an atmospheric layer, which can worsen air-pollution problems.

Humidity

Amount of water vapor in the atmosphere at a specific location on Earth’s surface.

Saturation

The point where the rate of water molecules leaving the surface equals the rate returning.

Relative humidity

Ratio of water vapor in a specific volume of air compared with how much that volume can actually hold, expressed as a percentage.

Dew point

Temperature at which air is cooled at constant pressure to reach saturation, allowing condensation to occur.

Latent heat

Stored energy in water vapor that is not released until condensation occurs.

Condensation nucleus

Small particle in the atmosphere around which cloud droplets can form.

Orographic lifting

Cloud formation that occurs when warm, moist air is forced to rise up the side of a mountain.

Cumulus

Puffy, lumpy-looking clouds that usually occur below 2000 m.

Stratus

Layered sheet-like cloud that covers much or all of the sky in a given area.

Cirrus

High clouds made of ice crystals that form at heights of 6000 m.

Precipitation

All solid and liquid forms of water that fall from clouds.

Coalescence

Process where cloud droplets collide and form larger droplets, eventually falling to Earth as precipitation.