Category: Define

Dry Line The boundary between the dry desert air mass of the Southwest U.S. and the moist air mass from the Gulf of Mexico. It

Dusk The period of waning light from the time of sunset to dark. Sunrise The daily disappearance of the sun below the western horizon as

Current A horizontal movement of water, such as the Gulf Stream off the east coast of North America, or air, such as the jet stream.

Dust Small particles of earth or other matter suspended in the air. Air This is considered the mixture of gases that make up the earth’s

Dust Devil A small, rapidly rotating column of wind, made visible by the dust, dirt or debris it picks up. It usually occurs in arid

Cyclone An area of closed pressure circulation with rotating and converging winds, the center of which is a relative pressure minimum. The circulation is counterclockwise

Dynamics A branch of mechanics that deals with forces and their relations to patterns of motion. In metorology, this relates especially to wind and water

Easterlies Usually applied to the broad patterns of persistent winds with an easterly component, such as the easterly trade winds. Wind Air that flows in

Dawn The first appearance of light in the eastern sky before sunrise. It marks the beginning of morning twilight. The visual display is created by

Easterly Wave An inverted, migratory wave-like disturbance or trough in the tropical region that moves from east to west, generally creating only a shift in