Glacial North Atlantic Deep/Intermediate Water.
Abbreviation for the GEWEX
Numerical Experimentation Panel, whose three primary
responsibilities are to promote the development of
interactive regional meso-scale and global-scale
model formulations of the land-surface, hydrological
and atmospheric processes that regulate the global
hydrologic cycle, river flow, and large-scale water
storage and evaporation; to organize numerical
experimentation/model intercomparison projects in
order to refine such model formulations and develop
predictions of these environmental properties; and
to promote the exploitation of field observations for
validation of interactive atmosphere-hydrological models
and the assimilation of such data in predictive regional
and global models.
The panel has identified four salient types of coordinated
atmospheric modeling experiments: (1) Land Surface
Data Assimilation System (LDAS) experiments (similar to
the PILPS project) where a land
surface model is driven by observed atmospheric data on
a continental scale; (2) Global Data Assimilation System
(GDAS) reanalysis experiments for the northern hemisphere
spring and summers of 1988 and 1993; (3) a free running
GCM approach wherein initial conditions from the spring of
1988 and 1993 (along with other boundary conditions from
the reanalysis) will be used to run ensembles of 1 to
3 month integrations to explore whether drought and flood
conditions can be reproduced; and (4) regional models with
reanalysis boundary conditions will be used to explore
whether regional models driven by global reanalyses can
provide high resolution regional estimates of circulation.
Three types of experiments were proposed for land-surface
hydrological comparisons: (1) regional calibration of
land surface process models for selected basins using
10-40 years of observed precipitation, potential evaporation
from the reanalysis, and observed river flow; (2) exploring
the sensitivity of GCMs to the LSP models using extreme
sets of parameters from the regional calibration of land
surface process models within a GCM; and (3) river routing
models to estimate the implied river flow for precipitation
from the reanalyses and from GCM or regional atmospheric
G-NEP Web site.
Acronym for the U.S. Global Ocean Atmosphere Land System program,
scheduled to run from 1995-2010. This program focuses on improving
the coupled ocean-atmosphere models used to simulate the structure of
El Nino events under the TOGA program, and
also to expand the investigation of predictability beyond the
tropical Pacific to other oceans and land masses.
See McPhaden (1995) and the
GOALS Web site.
Abbreviation for German Oceanographic Data Center.
- Goddard Space Flight Center
See the GSFC Web site.
Geosynchronous Operational Environmental Satellite.
GOES Web site.
Acronym for Global Ocean Euphotic Zone study, an
Acronym for Global Observation Information Network, a joint
Japanese-U.S. Earth observation initiative to strengthen
bilateral cooperation in Earth observatino information
networks involving both satellite and in-situ data.
GOIN Web site.
- golden spike
In chronostratigraphy, this is
the name given to the point at the base of each
stratotype section. The unique property
of this point is that here and here alone a defined point in rock
is known (by definition) to coincide with a defined point in time.
See Briggs and Crowther (1990), p. 462.
Acronym for the GCOS On-Line Data and Information
Management System, a system meant to provide access to information
of interest to members of the climate change research community.
More information can be found at the
GOLDIS Web site.
- Goldsborough-Stommel circulation
A circulation pattern found in models of enclosed basins
where the boundary condition is surface water forcing
using the natural, mass-flux boundary condition rather
than a rigid lid with
virtual salt forcing.
This results in a barotropic circulation pattern that is
similar to the wind-driven subtropical and subpolar gyres
but rotating in the reverse direction.
See McWilliams (1996) and
Huang and Schmitt (1993).
Acronym for Global Ocean Monitoring and Prediction, an
for monitoring and predicting ocean processes at a resolution
sufficient to depict features such as fronts and eddies. It
covers both deep and shallow water and uses a combination of
numerical ocean models, remotely sensed data, and in situ data
to develop ocean and ocean/atmosphere interface models aimed
at predicting the natural variability of the global ocean
system and its effect on short and long term climate
variability. A major aspect of this research is to determine
the origin of observed ocean anomalies and understand their
dynamics using a combination of satellite data, an eddy-resolving
global ocean model, and a comprehensive coastal model.
This is an NRL program whose principal investigators are
Harley Hurlburt and Ken Ferer.
GOMAP Web site.
Acronym for Global Ozone Monitoring Experiment, an instrument for
measuring ozone that will be launched on the second European
Remote Sensing Satellite (ERS-2). GOME is a nadir-viewing
spectrometer which will observe solar radiation transmitted
through or scattered from the Earth's atmosphere or from its
surface. The recorded spectra will be used to derive a
detailed picture of the atmosphere's content of ozone, nitrogen
dioxide, water vapor, oxygen/oxygen dimer, bromine oxide, and
other trace gases. The orbit will provide global Earth coverage
every three days.
GOME Web page.
Acronym for Global Ozone Monitoring by Occultation of Stars, an
Acronym for Global Ozone Monitoring Radiometer.
The name given to the
hypothetical southern hemisphere supercontinent consisting of
South America, Africa, Madagascar, India, Arabia, Malaya and the
East Indies prior to its breakup. The northern hemisphere analogue
was called Laurasia and both comprised
a theoretical single supercontinent called
Pangaea before breaking up.
1. Acronym for Global Ocean Observing System, a joint
ICSU/IOC-UNESCO/WMO program whose main
elements are the collection and timely distribution of oceanic
data and products, including assessments, assimilation of data
into numerical prediction models, the development and transfer
of technology, and capacity building within participating member
states to develop analysis and application capability.
See Smith (1993), the
International GOOS Web site, and the
U.S. GOOS Web site.
2. Acronym for Global Ozone Observing System.
Acronym for Geomagnetic Observing System.
Acronym for Global Ocean Surface Temperature Atlas.
Acronym for Gulf Offshore Weather Observing Network.
Abbreviation for the
Global Precipitation Climatology Project.
1. Abbreviation for GOES precipitation index.
2. Abbreviation for the geosynchronous precipitation index, which assigns
a constant precipitation rate for every pixiel having a brightness
temperature under a given threshold.
See Arkin and Meisner (1987).
Acronym for Gross Primary Production.
1. Abbreviation for Geophysical Processor System.
2. Abbreviation for Global Positioning System.
See the GPS Web site.
Informally this connotes the changing of some property over space
or time, e.g. there is a gradient in the density of the atmosphere
as one proceeds vertically upward or a gradient in SST
as one travels from the equator to the poles.
Formally, the gradient is the result of a
gradient operator operating
on some scalar quantity. The gradient of some scalar quantity f can
be mathematically expressed as
where is the gradient operator
and i,j,k and the component unit vectors
and differential operators in a Cartesian coordinate system.
See Dutton (1986).
- gradient operator
A differentiation operator, usually expressed by ,
that operates on scalar functions or
with a scalar or vector product on a vector. See
- gradient Richardson number
A dimensionless number expressing the ratio of the energy extracted
by buoyancy forces to the energy gained from the shear of the
large-scale velocity field.
It is expressed by
where N is the buoyancy frequency,
u the velocity, and z the vertical coordinate.
A flow is said to be stable if Ri is greater than 1/4, and if
it is less than 1/4 an instability may occur.
This form of the Richardson number therefore provides important
quantitative information on the relation between the stabilizing
effect of buoyancy and the destabilizing effect of velocity shear.
The definition of this is different than that for
the overall and
flux Richardson numbers.
See Turner (1973) and Dutton (1986).
- gradient wind
A wind that theoretically exists as a balance between the pressure
gradient, Coriolis, and centrifugal forces. It blows along curved
isobars with no tangential acceleration. In the case of rotation
around a high/low pressure area the centrifugal force is in the
same/opposite direction as the pressure gradient force and leads to
an increase/decrease in wind speed compared to that calculated for
the geostrophic wind resulting from a balance between the Coriolis
and pressure gradient forces.
- Grand Maximum
An extended period of maximum sunspot
activity that spanned the years 1100-1250 AD.
See Herman and Goldberg (1985).
- Grashof number
A dimensionless number that indicates the decay period of
internal wave fields. It is the square of
ratio of the dissipation
or diffusion time to the internal wave period
and is given by
where N is the internal wave frequency,
H the depth, and the kinematic viscosity.
A Grashof number greater than one indicates that the wave
field will decay very slowly, and if Gr is less than
one viscous dissipation damps the waves as fast as they
See Fischer et al. (1979).
- gravitational acceleration
The acceleration with which a body would freely fall under the
action of gravity in a vacuum. This actually varies with the
distance from the center of the Earth as well as with geographical
location (due to the inhomogeneities in the solid Earth), but the
internationally adopted value is 9.80665 m/s2 or 32.1740 ft/s2.
See global radiative-convective feedback.
Abbreviation for the
Global Runoff Data Center.
- Great Barrier Reef Undercurrent
See Church and Boland (1983).
- Great Lakes Environmental Research Laboratory (GLERL)
A NOAA laboratory located in Ann Arbor,
Michigan whose mission is to conduct integrated, interdisciplinary
environmental research in support of resource management and
environmental services in coastal and estuarine water, with
special emphasis on the Great Lakes.
GLERL Web site.
- Great Lakes Forecasting System (GLFS)
An operational system developed by The Ohio State University
and the NOAA GLERL
to make regularly scheduled predictions of the physical and
related variables of the Great Lakes. It consists of 3-D
numerical circulation and wave models, data assimilation,
objective analysis, rendering of results and verification, and
GLFS Web site.
- Great Salinity Anomaly
A freshening of the upper 500-800 m that propagated around
the North Atlantic subpolar gyre over a period of about 14 years.
It left the region of Iceland in the mid-to-late 1960s and returned
to the Greenland Sea in 1981-1982.
See Dickson et al. (1988).
- greenhouse effect
Short-wave solar radiation can pass through the clear atmosphere
relatively unimpeded, but long-wave radiation emitted by the warm
surface of the Earth is partially absorbed and then re-emitted
by a number of trace gases in the cooler atmosphere above. Since,
on average, the outgoing long-wave radiation balances the incoming
solar radiation, both the atmosphere and the surface will be warmer
than they would be without the greenhouse gases.
A historical perspective and tutorial can be found in
Jones and Henderson-Sellers (1990).
- greenhouse gas
Those gases that contribute to the
greenhouse effect by trapping heat within
the earth's atmosphere. The chief greenhouse gases are
carbon dioxide and water
vapor. Other potentially important trace gases are
ozone, and nitrous oxide. See
Watson et al. (1990) for a general overview and
Ramanathan et al. (1985) and
Ramanathan et al. (1987) for information on the
- Greenland Basin
A basin in the North Atlantic Ocean defined to the east
by Greenland, the west and south by the Mohn Ridge, and to
the north by Fram Strait. It has two abyssal plains separated
by the Greenland Fracture Zone
(at about 0 W, 76 N), with the Boreas plain to the
north being smaller and shallower (around 3200 m)
than the Greenland plain to the south (around 3600 m).
The Greenland Sea is completely
contained within the confines of the Greenland Basin.
- Greenland Sea
The regional sea in the North Atlantic Ocean which comprises
the waters in the Greenland Basin.
The average depth is about 2866 m.
In the summer, the volume of the Greenland Sea consists of
about 85% of the deep and bottom water masses (i.e.
Greenland Sea Deep Water (GSDW) and
Norwegian Sea Deep Water (NSDW)),
Arctic Intermediate Water (AIW),
and 9% surface water masses, mostly
Atlantic Water (AW).
See Swift (1986) and Hopkins (1991).
- Greenland Sea Deep Water
In physical oceanography, a water mass type
formed during the winter only in the central
of the gyre Greenland Sea, where the
cooling of surface water causes intense vertical convection. The
water sinks to the bottom in events related to the passage of storm
systems that last less than a week and occur in regions only a few
kilometers across. GSDW is the densest water mass in the
characterized by a salinity typically 34.88 to 34.90 and
very cold temperatures always under 0 C and typically
-1.1 to -1.3 C.
See Swift (1986) and Tomczak and Godfrey (1994).
- Greenwich Mean Time
Mean solar time referred to the zero
meridian of longitude that passes through Greenwich, England.
It is the basis for scientific and navigational purposes.
A strong northeast wind occurring chiefly in the cool season in the
south central Mediterranean. This is also used for the same phenomenon
in other parts of the Mediterranean, e.g. a ``gregal'' in France and
a ``grecale'' in the Tyhrrenian Sea.
- Gregorian calendar
The name given to the civil calendar now used in most countries of
the world. It is the Julian calendar as reformed by the decree of
Pope Gregory XIII in 1582. This reform omitted certain leap years
and brought the length of the year on which the calendar is based
nearer to the true astronomical value. It was designed to stay
synchronous with the equinoxes.
- grey body
See black body for the nonce.
Acronym for Global Resource Information Data Base, a
UNEP project that is a system of cooperating
centers dedicated to making special types of environmental
information more readily accessible to international and
national decision makers and environmental analysts.
GRID Web site.
Acronym for GReenland Icecore Project, a seven year (from
Jan. 1989 to Dec. 1995) ESF project
to retrieve and analyze a 3000m
long ice core drilled through the Greenland ice sheet at
its highest point, Summit. The objective was
to reveal the broad spectrum of information
on past environmental and climatic changes stored in the
See Dansgaard et al. (1993) and the
GRIP Web site.
Acronym for GCM-Reality Intercomparison Projects for
SPARC, a project to assess the present
state of troposphere-stratosphere general circulation
modeling, develop and implement strategies for model
intercomparisons, and improve their capabilities for
studying problems related to SPARC.
GRIPS Web site.
- Gros Morne Declaration
A statement concerning climate change that originated at the
International Workshop on Geological Indicators of Rapid
Environmental Change held on July 11-17, 1994 in Corner Brook
and Gros Morne National Park in Newfoundland, Canada.
The statement urged governments and other responsible
authorities to recognize the fundamental importance of
understanding natural and human-induced environmental changes.
Gros Morne Declaration Web site.
- Gross Primary Production
The total amount of carbon (or organic matter or energy) fixed by an
ecosystem, including the amount fixed but respired by the green
See Woodwell (1995a).
The sea-level pressure distribution averaged over a period during
which the essential characteristics of the atmospheric circulation
over a large region remain nearly unchanged.
- ground truth data
Geophysical parameter data, measured or collected by means
other than by the instrument itself, used as correlative or
calibration data for that instrument data, including data
taken on the ground or in the atmosphere. Ground truth data
are another measurement of the phenomenon of interest; they
are not necessarily more "true" or more accurate than the
- group velocity
See Trefethen (1982).
- growth efficiency
In marine ecology, the annual weight increment of the
consumers divided by the weight
of food consumed. This is one of two factors comprising
the ecological efficiency.
See Barnes and Hughes (1988).
- growth heterochrony
A type of heterochrony involving
the changes in shape of individual structures produced during
an organism's ontogeny, i.e. the
phylogenetic changes shown by the
structures as they vary their rate of shape change.
The change in relative size of the same number of spines
in a descendant would be an example of this. Compare to
See Briggs and Crowther (1990), Ch. 2.4.
Acronym for the Geological Society of America, an organization founded
in 1888 to provide access to elements essential to the professional
growth of earth scientists at all levels of expertise. It presently
has over 15,000 members, and more information about it can be found at
the GSA Web site.
Abbreviation for Global Subsurface Data Center.
Greenland Sea Deep Water.
Goddard Space Flight Center.
Abbreviation for Greenland Sea Project, a co-sponsored
project aimed at observing and
modeling the atmospheric, ice, oceanic and biological processes
relevant to understanding the role of the Nordic Seas in the
climate system. The GSP was in operation from 1987-1993 and
has been superseded by ESOP.
The data collected during GSP can be found at the
GSP Web site.
Abbreviation for Global Soil Wetness Project, a
ISLSCP pilot study of the feasibility of
producing a global data set of soil etness and related
surface flux estimates using meteorological observations and
analyses to drive state-of-the-art land surface models.
GSWP Web site.
Abbreviation for the Global Tropospheric Chemistry Program.
See the GTCP Web site.
Abbreviation for Gas Tension Device, an instrument which allows in-situ
measurements of the rate at which gases pass through the ocean surface
to be made. This was developed at the IOS.
Abbreviation for the Global Tropospheric Experiment, the NASA
contribution to the GTCP. It is a program
designed to use aircraft and satellite observations of meteorology,
land use, and atmospheric chemical species to aid in experiment
design and in the scientific analysis of results obtained from
ground-based measurements. See the
GTE Web site.
Global Terrestrial Observing System.
Abbreviation for Global Temperature and Salinity Pilot Program,
the primary goal ofwhich is to make global measurements of ocean
temperature and salinity quickly and easily accessible to users.
It seeks to develop adn maintain a global ocean T-S resource
with data that are both up-to-date and of the highest possible
GTSPP Web site.
Acronym for GUlF of MEXico experiment.
See Lewis et al. (1989).
- Guiana Basin
An ocean basin located off the Venezuela, Guiana and
Brazilian coasts in the west-central Atlantic Ocean.
This comprises the western Demerara Abyssal Plain
and the eastern Ceara Abyssals Plain, separated by
the Amazon abyssal cone. This has also been called the
See Fairbridge (1966).
- Guinea Basin
An ocean basin located on the equator off the west coast
of Africa. It includes the Guinea Abyssal Plain and has
also been called the West African Trough.
See Fairbridge (1966).
- Guinea Current
The part of the cyclonic gyre that forms the
Guineau Dome that flows
northwestward along the west African coast.
- Guineau Dome
A doming of the thermocline in the summer at approximately
10 N and 22 W off the coast off of Dakar in west
Africa. This is due to a small cyclonic gyre driven by
part of the
North Equatorial Countercurrent heading north combining with
North Equatorial Undercurrent.
See double tide.
- Gulf of Alaska
See Royer and Emery (1987).
- Gulf of Bothnia
The northern section of the
Baltic Sea. It is further divided into
the northern Bay of Bothnia and the southern Bothnian Sea, the
latter of which adjoins the Aland Sea
to the south.
- Gulf of California
- Gulf of Carpenteria
- Gulf of Finland
A part of the Baltic Sea which
adjoins the Aland Sea and the
main Baltic to the west and is landlocked elsewhere.
- Gulf of Mexico
Much more later.
- Gulf of Oman
- Gulf of Riga
A part of the Baltic Sea connected to both
the Gulf of Finland to the north and
the Baltic Sea proper to the west via narrow passages between the
islands of Saaremaa and Hiiumaa and the mainland.
- Gulf of Suez
- Gulf of Thailand
- Gulf Stream
Much, much more later.
The Alpine name for the Nebraskan
A meteorological phenomenon that combines some of the characteristic
features of both dust devils and
tornadoes. It is a tornado-like
vortex that appears to develop on the ground and extend several
hundred feet upward. These generally develop along the leading
edge of a thunderstorm cell's outflow boundary and are of
limited duration, although they can be strong enough to cause
- gust front
The front created when downdraft or
downburst air reaches the ground
and spreads out. These have been observed to be 100 to 1000 m
deep, 5 to 100 km wide, last for 2 to 20 minutes, and spread
with speeds of 5 to 15 m/s.
Gust fronts are also capable of triggering new thunderstorms
as the air in the boundary layer is forced to rise over the
The phenomenon of plants exuding water as a liquid, seen especially
in trees of hot, wet forests.
See Collinson (1988).
- Guyana Current
A northwestward flowing current along the eastern coast of South
America from the Equator to around 10 N after which point the
northwestward flowing current is called the
Below the equator the northward flow component that becomes the
Guyana Current is called the
North Brazil Current.
The currents in this region have not been extensively studied,
with this one being perhaps the least well known, even to the
point that some researchers doubt its existence as a continous
feature of the general circulation. The fact remains that there
is some sort of average northward flow in this area since the
fresh water signal from the Amazon River does reach the
Mediterranean Sea as a surface layer of low salinity. The
matter of calling it a current or perhaps just an average
northward drift can only be decided via further
Abbreviation for GEWEX Water Vapor Project, the goal
of which is the accurate global measurement, modelling, and long-term
prediction of water vapor. See the
GVaP Web site for further information.
Abbreviation for the Global Vegetation Index dataset.
See Tarpley et al. (1984).
Abbreviation for Global Weather Experiment, which ran from Dec. 1978
to Nov. 1979. It was a plan to observe the atmosphere as systematically
as possible using the most advanced technology then available. The
operational observing network was enhanced with special observing
systems such as drifting buoys to measure surface variables over the
oceans, dropwindsondes ejected from aircraft, and constant-level
balloons to observe the upper circulation to provide a comprehensive
global meteorological data set. See Daley (1991).
Global Warming Potential.
Abbreviation for Gravity Wave Processes and Parameterizations,
a SPARC initiative to produce a
climatology for gravity waves in atmospheric models and to
assess the needs in terms of instrumentation, data analysis
and modeling. See the
GWPP Web site.