| A | B |
|---|
| sublimation | the process in which a solid changes directly into a gas (term sometimes also used for the reverse process) |
| dew point | at constant pressure & water vapor content, temperature at which rate of condensation equals rate of evaporation |
| absolute humidity | mass of water vapor per unit volume of air that contains the water vapor (grams of water vapor per cubic meter of air) |
| relative humidity | 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 | collection of small water droplets or ice crystals suspended in the air; forms when air is cooled & condensation occurs |
| condensation nucleus | a solid particle in the atmosphere that provides the surface on which water vapor condenses |
| adiabatic cooling | process by which the temperature of an air mass decreases ast he air mass rises & expands |
| advective cooling | 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 & that commonly forms at very low altitudes |
| cumulus cloud | a low-level, billowy cloud that commonly has a top that resembles cotton balls & a dark bottom |
| cirrus cloud | a feathery cloud that is composed of ice crystals & 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 | formation of a large droplet by the combination of smaller droplets |
| supercooling | condition where a substance is cooled below its freezing, condensation, or sublimation point without going through a change of state |
| cloud seeding | process of introducing freezing nuclei or condensation nuclei into a cloud in order to cause rain to fall |
