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.
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