Gn-Gz

 

GNAIW

Abbreviation for Glacial North Atlantic Deep/Intermediate Water.

 

G-NEP

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 model runs. See the G-NEP Web site.

 

GOALS

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.

 

GODC

Abbreviation for German Oceanographic Data Center. See DOD.

 

Goddard Space Flight Center

See the GSFC Web site.

 

GOES

Acronym for Geosynchronous Operational Environmental Satellite. See the GOES Web site.

 

GOEZ

Acronym for Global Ocean Euphotic Zone study, an IGBP project.

 

GOIN

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. See the 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.

 

GOLDIS

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).

 

GOMAP

Acronym for Global Ocean Monitoring and Prediction, an SERDP program 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. See the GOMAP Web site.

 

GOME

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. See the GOME Web page.

 

GOMOS

Acronym for Global Ozone Monitoring by Occultation of Stars, an ESA project.

 

GOMR

Acronym for Global Ozone Monitoring Radiometer.

 

Gondwanaland

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.

 

GOOS

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.

 

GOS

Acronym for Geomagnetic Observing System.

 

GOSTA

Acronym for Global Ocean Surface Temperature Atlas.

 

GOWON

Acronym for Gulf Offshore Weather Observing Network.

 

GPC

Abbreviation for gas-to-particle conversion.

 

GPCP

Abbreviation for the Global Precipitation Climatology Project.

 

GPI

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).

 

GPP

Acronym for Gross Primary Production.

 

GPS

1. Abbreviation for Geophysical Processor System. 2. Abbreviation for Global Positioning System. See the GPS Web site.

 

gradient

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, divergence, and curl.

 

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 are formed. 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.

 

GRC

See global radiative-convective feedback.

 

GRDC

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. See the 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 image production. See the 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 chlorofluorocarbons, methane, 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 trace gases.

 

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)), 9% 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 Greenland Sea, 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.

 

gregale

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.

 

GRID

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. See the GRID Web site.

 

GRIP

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 ice. See Dansgaard et al. (1993) and the GRIP Web site.

 

GRIPS

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. See the 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. See the 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 plants. See Woodwell (1995a).

 

grosswetterlage

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 instrument data.

 

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 differentiative heterochrony. See Briggs and Crowther (1990), Ch. 2.4.

 

GSA

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.

 

GSDC

Abbreviation for Global Subsurface Data Center.

 

GSDW

Abbreviation for Greenland Sea Deep Water.

 

GSFC

Abbreviation for Goddard Space Flight Center.

 

GSP

Abbreviation for Greenland Sea Project, a co-sponsored AOSB/ICES 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.

 

GSWP 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. See the GSWP Web site.

 

GTCP

Abbreviation for the Global Tropospheric Chemistry Program. See the GTCP Web site.

 

GTD

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.

 

GTE

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.

 

GTOS

Abbreviation for Global Terrestrial Observing System.

 

GTSPP

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 quality. See the GTSPP Web site.

 

GUFMEX

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 Makaroff Deep. 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 the North Equatorial Undercurrent.

 

gulder

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

More later.

 

Gulf of Carpenteria

More later.

 

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

More later.

 

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

More later.

 

Gulf of Thailand

More later.

 

Gulf Stream

Much, much more later.

 

Gunz

The Alpine name for the Nebraskan glacial period.

 

gustnado

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 wind damage.

 

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 advancing front.

 

guttation

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 Caribbean Current. 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 measurements.

 

GVaP

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.

 

GVI

Abbreviation for the Global Vegetation Index dataset. See Tarpley et al. (1984).

 

GWE

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).

 

GWP

Abbreviation for Global Warming Potential.

 

GWPP

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.