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Chapter 20
Water In The Atmosphere.
Term | Definition |
---|---|
latent heat | the heat energy that is absorbed or released by a substance during a phase change. |
sublimation | the process in which a solid changes directly into a gas (the term is sometimes also used for the reverse process). |
dew point | at constant pressure and water vapor content, the temperature at which the rate of condensation equals the rate of evaporation. |
absolute humidity | the mass of water vapor per unit volume of air that contains the water vapor, usually expressed as grams of water vapor per cubic meter of air. |
relative humidity | the ratio of the amount of water vapor in the air to the amount of water vapor needed to reach saturation at a given temperature. |
cloud | a collection of small water droplets or ice crystals suspended in the air, which forms when the air is cooled and condensation occurs. |
condensation nucleus | a solid particle in the atmosphere that provides the surface on which water vapor condenses. |
adiabatic cooling | the process by which the temperature of an air mass decreases as the air mass rises and expands |
advective cooling | the process by which temperature of an air mass decreases as the air mass moves over a cold surface. |
stratus cloud | a gray cloud that has a flat, uniform base and that commonly forms at very low altitudes. |
cumulus cloud | a low-level billowy cloud that commonly has a top that resembles cotton balls and a dark bottom. |
cirrus cloud | a feathery cloud that is air composed of ice crystals and that has the highest altitude of any cloud in the sky. |
fog | water vapor that has condensed very near the surface of earth because air close to the ground has cooled. |
precipitation | any form of water that falls to Earth's surface from the clouds; includes rain, snow, sleet, or hail. |
coalescence | the formation of a large droplet by the combination of smaller droplets. |
supercooling | a condition in which a substance is cooled below its freezing point, or sublimation point, without going through a change of state. |
cloud seeding | the process of introducing freezing nuclei or condensation nuclei into a cloud in order to cause rain to fall. |