Subj : Wx Terms (G)(1) To : All From : Daryl Stout Date : Wed Nov 08 2017 12:05 am G Gusts- A rapid fluctuation of wind speed with variations of 10 knots or more between peaks and lulls. G/KG Grams per Kilogram Gage In hydrologic terms, 1) A device for indicating the magnitude or position of a thing in specific units, when such magnitude or position undergoes change, for example: The elevation of a water surface, the velocity of flowing water, the pressure of water, the amount or intensity of precipitation, the depth of snowfall, etc. 2) The act or operation of registering or measuring the magnitude or position of a thing when these characteristics are undergoing change. 3) The operation, including both field and office work, of measuring the discharge of a stream of water in a waterway. Gage Datum A horizontal surface used as a zero point for measurement of stage or gage height. This surface usually is located slightly below the lowest point of the stream bottom such that the gage height is usually slightly greater than the maximum depth of water. Because the gage datum is not an actual physical object, the datum is usually defined by specifying the elevations of permanent reference marks such as bridge abutments and survey monuments, and the gage is set to agree with the reference marks. Gage datum is a local datum that is maintained independently of any national geodetic datum. However, if the elevation of the gage datum relative to the national datum (North American Vertical Datum of 1988 or National Geodetic Vertical Datum of 1929) has been determined, then the gage readings can be converted to elevations above the national datum by adding the elevation of the gage datum to the gage reading. Gaging Station In hydrologic terms, a particular site on a watercourse where systematic observations of stage/ and or flow are measured. Gale An extratropical low or an area of sustained surface winds of 34 (39 mph) to 47 knots (54 mph). Gale Warning A warning of sustained surface winds, or frequent gusts, in the range of 34 knots (39 mph) to 47 knots (54 mph) inclusive, either predicted or occurring, and not directly associated with a tropical cyclone. Gallery In hydrologic terms, a passageway within the body of a dam or abutment. Gamma A unit of magnetic field intensity equal to 1 x 10.0-5 Gauss; also equal to 1 nanotelsa (nT). Gamma Ray A type of electromagnetic radiation with a very short wavelength and high energy level. Generally, emitted during radioactive decay of a substance. Gap Winds Strong winds channeled through gaps in the Pacific coastal ranges, blowing out into the Pacific Ocean or into the waterways of the Inside Passage. The winds blow through low passes where major river valleys issue onto the seaways when strong east-west pressure gradients exist between the coast and the inland areas, with low pressure over the ocean. Gas Laws The thermodynamic laws pertaining to perfect gases, including Boyle's law, Charles' law, Dalton's law and the equation of state. Gate In hydrologic terms, a device in which a leaf or member is moved across the waterway from an external position to control or stop flow. There are many different kinds of gates used on a dam. Gauss The unit of magnetic induction in the cgs (centimeter-gram- second) system. Gaussian Plume Model A computer model used to calculate air pollution concentrations. The model assumes that a pollutant plume is carried downwind from its emission source by a mean wind and that concentrations in the plume can be approximated by assuming that the highest concentrations occur on the horizontal and vertical midlines of the plume, with the distribution about these mid-lines characterized by Gaussian- or bell-shaped concentration profiles. Gaussian Puff Model A model used to calculate air pollution concentrations. The model assumes that a continuously emitted plume or instantaneous cloud of pollutants can be simulated by the release of a series of puffs that will be carried in a time- and space-varying wind field. The puffs are assumed to have Gaussian or bell-shaped concentration profiles in their vertical and horizontal planes. GDR On a buoy report, direction, in degrees clockwise from true North, of the GSP, reported at the last hourly 10-minute segment. GEMPAK General Environmental Meteorological Package (programming language). GEN General General Circulation The totality of large-scale organized motion for the entire global atmosphere. General Circulation Models (GCMs) - These computer simulations reproduce the Earth's weather patterns and can be used to predict change in the weather and climate. General Wind Land management agency term for winds produced by synoptic-scale pressure systems on which smaller-scale or local convective winds are superimposed. Geohydrology In hydrologic terms, the branch of hydrology relating to subsurface, or subterranean waters. Geomagnetic Elements In solar-terrestrial terms, the components of the geomagnetic field at the surface of the earth. In SESC use, the northward and eastward components are often called the H and D components, where the D component is expressed in gammas and is derived from D (the declination angle) using the small angle approximation. Geomagnetic Field The magnetic field observed in and around the earth. The intensity of the magnetic field at the earth's surface is approximately 0.32 gauss at the equator and 0.62 gauss at the north pole. Geomagnetic Storm In solar-terrestraial terms, a worldwide disturbance of the earth's magnetic field, distinct from regular diurnal variations. Minor Geomagnetic Storm: A storm for which the Ap index was greater than 29 and less than 50. Major Geomagnetic Storm: A storm for which the Ap index was greater than 49 and less than 100. Severe Geomagnetic Storm: A storm for which the Ap index was 100 or more. Initial Phase: Of a geomagnetic storm, that period when there may be an increase of the middle-latitude horizontal intensity (H). Main Phase: Of a geomagnetic storm, that period when the horizontal magnetic field at middle latitudes is generally decreasing. Recovery Phase: Of a geomagnetic storm, that period when the depressed northward field component returns to normal levels. Geophysical Events In solar-terrestrial terms, flares (Importance two or larger) with Centimetric Outbursts (maximum of the flux higher than the Quiet Sun flux, duration longer 10 minutes) and/or strong SID. Sometimes these flares are followed by Geomagnetic Storms or small PCA. (Class M Flares). Geophysics In hydrologic terms, the study of the physical characteristics and properties of the earth; including geodesy, seismology, meteorology, oceanography, atmospheric electricity, terrestrial magnetism, and tidal phenomena. Geopotential Height The 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 level of the atmosphere over that station at which the atmospheric pressure is 500 mb is 5600 meters above sea level. This is an estimated height based on temperature and pressure data. Geostationary Satellite A satellite that rotates at the same rate as the earth, remaining over the same spot above the equator. Geostrophic Wind A 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). Geosynchronous Term applied to any equatorial satellite with an orbital velocity equal to the rotational velocity of the earth. The net effect is that the satellite is virtually motionless with respect to an observer on the ground. GF Ground Fog- Fog produced over the land by the cooling of the lower atmosphere as it comes in contact with the ground. Also known as radiation fog, and in parts of California as tule fog. --- þ Synchronet þ The Thunderbolt BBS - wx1der.dyndns.org .