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 the 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 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, and hail |
Coalescence | The formation of a larger droplet by the combination of smaller droplets |
Supercooling | A condition in which a substance is cooled below its freezing point, condensation 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 |