GeohydrologyGeological study of the character, source, and mode of ground water.
Geomagnetic ElementsIn solar-terrestrial terms, the components of the geomagnetic field at the surface of the earth.
Geomagnetic FieldThe magnetic field observed in and around the earth. The intensity of the magnetic field at the earth's surface is approximately 0.
Geomagnetic StormIn solar-terrestraial terms, a worldwide disturbance of the earth's magnetic field, distinct from regular diurnal variations.
Geophysical EventsIn solar-terrestrial terms, flares (Importance two or larger) with Centimetric Outbursts (maximum of the flux higher than the Quiet Sun flux, duration…
geophysical focus areasSix identified focus areas for ARM's data collection and research activities. These focus areas are shortwave radiation, longwave radiation, clouds…
GeophysicsRefers to the physics of the earth, e.g., seismology, oceanography, volcanology, geomagnetism, etc.
Geopotential HeightThe height above sea level of a pressure level. For example, if a station reports that the 500 mb height at its location is 5600 m, it means that the…
GeosphereThe soils, sediments, and rock layers of the Earth's crust, both continental and beneath the ocean floors.
Geostationary SatelliteA satellite that rotates at the same rate as the earth, remaining over the same spot above the equator.
geostraphic windA theoretical horizontal wind blowing in a straight path, parallel to the isobars or contours, at a constant speed.
Geostrophic WindA wind that is affected by coriolis force, blows parallel to isobars and whose strength is related to the pressure gradient (i.e., spacing of the isobars).
GeosynchronousRefers to an orbit (about 22,300 miles above Earth’s surface) with a period equal to one day.
Geothermal energyEnergy produced by the internal heat of the earth; geothermal heat sources include: hydrothermal convective systems; pressurized water reservoirs; hot dry…
GFGround Fog- Fog produced over the land by the cooling of the lower atmosphere as it comes in contact with the ground.
GFS(Global Forecast System) One of the operational forecast models run at NCEP. The GFS is run four times daily, with forecast output out to 384 hours.
GISP2Greenland Ice Sheet Project 2, the second phase of an effort by a group of scientists to produce long records of climate by drilling at the summit of the…
glaciala time interval characterized by widespread glacial ice, see also "Ice Age".
GlaciationThe transformation of cloud particles from water drops to ice crystals. Thus, a cumulonimbus cloud is said to have a "glaciated" upper portion.
GlacierBodies of land ice that consist of recrystallized snow accumulated on the surface of the ground, and that move slowly downslope.
Glacier Dammed LakeThe lake formed when a glacier flows across the mouth of an adjoining valley and forms an ice dam.
Glacier WindA shallow downslope wind above the surface of a glacier, caused by the temperature difference between the air in contact with the glacier and the free air…
GlazeIce formed by freezing precipitation covering the ground or exposed objects.
GLF(Open Lakes Forecast) - A National Weather Service marine forecast product for the U.S.
Global Forecast System(GFS)- One of the operational forecast models run at NCEP. The GFS is run four times daily, with forecast output out to 384 hours.
Global Observing SystemGlobal Observing System (GOS) Global network of observational stations which is the coordinated system of methods, techniques and facilities for making…
Global Positioning System (GPS)(GPS)A navigation system which uses a constellation of artificial earth satellites to make precise determinations of the latitude and longitude of locations on…
Global Telecommunication SystemGlobal Telecommunication System (GTS) The coordinated global system of telecommunication facilities and arrangements for the rapid collection, exchange…
Global Temperature ChangeThe net result of four primary factors including the greenhouse effect, changes in incoming solar radiation, altered patterns of ocean circulations, and…
Global WarmingA popular term used to describe the increase in average global temperatures due to the greenhouse effect.
Global Warming Potential (GWP)Global Warming Potential (GWP) is defined as the cumulative radiative forcing effects of a gas over a specified time horizon resulting from the emission…
GloryAn optical effect characterized by concentric rings of color (red outermost and violet innermost) surrounding the shadow of an observer's head when the…
GLS(Great Lakes Storm Summary) A National Weather Service forecast product providing updated information whenever a storm warning is in effect on any of the…
GMDSS(Global Maritime Distress and Safety System)- The Global Maritime Distress and Safety System (GMDSS) is intended to provide more effective and efficient…
GMNOn a buoy report, the minute of the hour that the GSP occurred, reported at the last hourly 10-minute segment.
GMTGreenwich Mean Time (now known as Universal Coordinated Time)
GOESGeostationary Operational Environmental Satellite- Satellites orbiting at 22,370 miles above the Earth's surface with the same rotational velocity as the…
GPSAn acronym for Global Positioning System. A network of satellites which provide extremely accurate position and time information.
GRADGradient- A rate of change with respect to distance of a variable quantity, as temperature or pressure, in the direction of maximum change.
GradientGeneral slope or rate of change in vertical elevation per unit of horizontal distance of water surface of a flowing stream.
Gradient High WindsThese high winds usually cover a large area and are due to synoptic-scale, extra-tropical low pressure systems.
Gradient windGradient wind The same as geostrophic wind, but blowing parallel to curved isobars or contours.
Gradual CommencementIn solar-terrestrial terms, the commencement of a geomagnetic storm that has no well-defined onset
GranulationIn solar-terrestrial terms, the cellular structure of the photosphere visible at high spatial resolution.
GrasslandTerrestrial ecosystem (biome) found in regions where moderate annual average precipitation (25 to 76 centimeters or 10 to 30 inches) is enough to support…
Great Circle TrackA great-circle track is the shortest distance between two points on a sphere, and when viewed on a 2-dimensional map the track will appear curved.
Great Lakes FaxbackDissemination systems housed at Weather Forecast Office (WFO) Cleveland by which Great Lakes customers request and receive hard copies of selected marine…
Great Lakes Freeze-Up/Break-Up Outlook(FBO) - A National Weather Service product to keep mariners informed of the projected freeze-up date or break-up date of ice on the Great Lakes.
Great Lakes Storm Summary(GLS) - A National Weather Service forecast product providing updated information whenever a storm warning is in effect on any of the Great Lakes.
Great Lakes Weather Broadcast(LAWEB) - A National Weather Service product containing an observation summary prepared to provide Great Lakes mariners with a listing of weather…
Green LineThe green line is one of the strongest (and first-recognized) visible coronal lines. It identifies moderate temperature regions of the CORONA.
Greenhouse EffectA popular term used to describe the heating effect due to the trapping of long wave (length) radiation by greenhouse gases produced from natural and human…
Greenhouse GasSome greenhouse gases, which contribute to the greenhouse effect, occur naturally in the atmosphere while others result from human activities such as the…
Greenhouse Gas (GHG)Any gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include, but are not limited to, water vapor, carbon dioxide (CO2), methane…
Greenhouse GasesThose gases, such as water vapor, carbon dioxide, tropospheric ozone, methane, and low level ozone that are transparent to solar radiation, but opaque to…
Greenland HighGreenland High The anticyclone that appears to overlie Greenland; analogous to the Antarctic anticyclone.
Greenwich Mean Time (GMT)(GMT)Same as Coordinated Universal Time (UTC); the international time standard kept at Greenwich, England.
GRIB(Gridded Binary Format) - A format used for meteorological data. Typically used in the past for computer generated model data but will be used…
GridA common term referring to an electricity transmission and distribution system.
Grids1) Squared off areas across the terrain used to define forecast areas. Often 5x5 or 2.5x2.5 kilometer in size.
Ground Blizzard WarningWhen blizzard conditions are solely caused by blowing and drifting snow.
Ground ClutterA pattern of radar echoes from fixed ground targets (buildings, hills, etc.) near the radar.
Ground Fog(abbrev. GF) Fog produced over the land by the cooling of the lower atmosphere as it comes in contact with the ground.
Ground Heat FluxThe flux of heat from the ground to the earth's surface; a component of the surface energy budget.
Ground receive sitesA satellite dish and associated computer which receives signals from the GOES satellite, decodes the information, and transmits it to a another site for…
Ground StrokeThe current that propagates along the ground from the point where a direct stroke of lightning hits the ground.
Ground WaterWater that flows or seeps downward and saturates soil or rock, supplying springs and wells.
Ground Water DivideA line on a water table where on either side of which the water table slopes downward.
Ground Water FlowStreamflow which results from precipitation that infiltrates into the soil and eventually moves through the soil to the stream channel.
Ground Water HydrologyThe branch of hydrology that specializes in ground water; its occurrence and movements; its replenishment and depletion; the properties of rocks that…
Ground Water OutflowThat part of the discharge from a drainage basin that occurs through the ground water.
Ground Water RunoffThat part of the runoff which has passed into the ground, has become ground water, and has been discharged into a stream channel as spring, or seepage…
Grounded iceIce that has run aground or is contact with the ground underneath it.
Group VelocityThe speed at which a particular wave front or swell train advances.
Grout CurtainA barrier produced by injecting grout into a vertical zone, usually narrow (horizontally), and in the foundation to reduce seepage under a dam.
Growing Degree DayThe number of degrees that the average temperature is above a baseline value. For example, 40 degrees for canning purposes; 45 degree for potatoes; and 50…
Growing SeasonThe period, often the frost-free period, during which the climate is such that crops can be produced.
GrowlerSimilar to a bergy bit, but smaller, extending less than 1 meter above the sea surface and occupying an area of 20 square meters or less.
Gulf StreamWarm water current extending from the Gulf of Mexico and Florida up the U.S. east coast then east northeast to Iceland and Norway.
GungeSlang for anything in the atmosphere that restricts visibility for storm spotting, such as fog, haze, precipitation (steady rain or drizzle), widespread…
Gust(Abbrev. G) - A rapid fluctuation of wind speed with variations of 10 knots or more between peaks and lulls.
Gust FrontThe leading edge of gusty surface winds from thunderstorm downdrafts; sometimes associated with a shelf cloud or roll cloud.
Gustnado(or Gustinado) - [Slang], gust front tornado. A small tornado, usually weak and short-lived, that occurs along the gust front of a thunderstorm.