Science / Weather Glossary

Geostationary Satellite: An orbiting weather satellite that maintains the same position over the equator during the earth's rotation. Also known as GOES, an acronym for Geostationary Operational Environmental Satell . . . View Full Definition

Geostrophic Wind: A steady horizontal motion of air along straight, parallel isobars or contours in an unchanging pressure or contour field. It is assumed that there is no friction, that the flow is straight . . . View Full Definition

Glacier Winds: Air flow that descends from glaciers, occasionally at a high rate of speed. Caused by the temperature difference between the air in contact with the glacier and the air at the same altitude, . . . View Full Definition

Glaze: A smooth clear icy coating of supercooled water droplets that spread out and freeze onto objects on contact. A storm that produces the accretion of glaze is called an ice storm.

Gradient Wind: A steady horizontal air motion along curved parallel isobars or contours in an unchanging pressure or contour field, assuming there is no friction and no divergence or convergence.

Graupel: A form of frozen precipitation consisting of snowflakes or ice crystals and supercooled water droplets frozen together.

Gravitation: The mutual attraction between two masses of matter. The rotation of the earth and the atmosphere modifies this attraction to produce the field of gravity.

Gravity: The force of attraction of the earth on an object. The direction is downward relative to the earth, and it decreases with elevation or altitude away from the earth's surface.

Green Flash: A brilliant green coloration of the upper edge of the sun, occasionally seen as the sun's apparent disk is about to set below a clear horizon.

Greenhouse Effect: The overall warming of the earth's lower atmosphere primarily due to carbon dioxide and water vapor which permit the sun's rays to heat the earth, but then restrict some heat-energy from esc . . . View Full Definition

Greenwich Mean Time (GMT): The name of the twenty-four hour time scale which is used throughout the scientific and military communities. Standard Time begins at Greenwich, England, home of the Royal Observatory which . . . View Full Definition

Ground Clutter: A pattern of radar echoes reflecting off fixed ground targets such as buildings or hills near the radar. This may hide or confuse the proper return echo signifying actual precipitation.

Ground Fog: Fog created when radiational cooling at the earth's surface lowers the temperature of the air near the ground to or below its initial dew point. Primarily takes place at night or early morning.

Growing Season: Considered the period of the year during which the temperature of cultivated vegetation remains sufficiently high enough to allow plant growth. Usually considered the time period between the . . . View Full Definition

Gulf Stream: The warm, well-defined, swift, relatively narrow ocean current which exists off the east coast of the United States, beginning near Cape Hatteras. The term also applies to the oceanic system . . . View Full Definition

Gully Washer: A heavy rain shower that occurs suddenly, possibly creating a flash flood.

Gust: A sudden significant increase in or rapid fluctuations of wind speed. Peak wind must reach at least 16 knots (18 miles per hour) and the variation between peaks and lulls is at least 10 knot . . . View Full Definition

Gust Front: The leading edge of the cool, gusty surface winds produced by thunderstorm downdrafts. Sometimes confused with an outflow boundary.

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