Ga-Gm

 

Gaia hypothesis

The hypothesis that the Earth's physical and biological systems are considered to be a complex and self-equilibrating entity. See Lovelock (1979).

 

GAIM

Acronym for Global Analysis, Interpretation and Modelling, a subprogram of the the IGBP to analyze current models and data, assess the capability of current models and experimental programs to resolve key questions, and advance and sythesize our understanding of the global biogeochemical cycles and their links to the hydrological cycle and to the physical-climate system as a whole. See the GAIM Web site.

 

galactic circle

The great circle of the celestial sphere in where it is cut by the galactic plane. It is the primary circle to which the galactic coordinates are referred.

 

galactic plane

The plane passing as nearly as possible through the center of the belt known as the Milky Way or Galaxy.

 

GALE

Acronym for the Genesis of Atlantic Lows Experiment, an extensive study of the atmospheric processes involved in the development of winter storms on the East Coast of the United States. See the GALE Web site.

 

GAME

Acronym for the GEWEX Asian Monsoon experiment, the goal of which is to understand the role of the Asian monsoon in the global climate system and develop methods for long-range forecasting. See the GAME Web site for further information.

 

GAMES

Acronym for Global Aerosols Monitoring Experiment from Space.

 

GAPA

Acronym for the International Geological-Geophysical Atlases of the Atlantic and Pacific Oceans, an ocean mapping activity of the IOC.

 

GARP

Acronym for the Global Atmospheric Research Program, planned and coordinated jointly starting in 1968 by the WMO and the ICSU.

 

GASTON

Abbreviation for Glace Atmosphere sur Terre et Ocean Numeriques, a group performing numerical simulations of coupled ocean, atmosphere and ice models. For further details, see the GASTON Web site.

 

gas-to-particle conversion

In the study of atmospheric aerosols, GPC is a mechanism for the production of nucleation mode type atmospheric aerosols where condensation of gaseous substances causes either the growth of existing nuclei (heterogeneous nucleation) or the formation of new particles (homogeneous nucleation). The former can proceed at minor supersaturations while the latter requires a much greater degree of supersaturation. Converted sulfates, nitrates and hydrocarbons are three major components suspected of being involved in GPC. See Jaenicke (1993b).

 

GATE

Acronym for GARP Atlantic Tropical Experiment.

 

Gauss Magnetic Epoch

Normal polarity time interval extending from 2.4 to 3.3 million years ago. See Bowen (1991).

 

Gaussian distribution

More about which later.

 

GAW

Acronym for the Global Atmospheric Watch program, the purpose of which is to provide data, scientific assessments, and other information on the atmospheric composition and related physical characteristics of the background atmosphere from all parts of the globe. The measurement program includes greenhouse gases, ozone, radiation and optical depth, precipitation chemistry, chemical and physical properties of aerosols, reactive gases, radionuclides, and related meterological parameters. See the GAW Web site.

 

GCCIP

Abbreviation for the Global Climate Change Information Programme, a program established in Oct. 1991 to provide an link for information about climate change among scientists, politicians, economists, and the general public. GCCIP is a part of ARIC. See the GCCIP Web site.

 

GCD

Abbrevation for General Circulation Drifter.

 

GCDC

Abbreviation for Global Change Data Center, a part of the NASA/GSFC's ESD whose mission is to develop and operate data systems, generate science products, and provide archival and distribution services for earth science data in support of the USGCP and the NASA MTPE. See the GCDC Web site for further information.

 

GCDIS

Acronym for Global Change Data and Information System, a proposed IWG structure that encompasses the ensemble of multi-agency and institution data and information systems supporting the Global Change Research Program (GCRP) and IGBP. GCDIS may be more broadly viewed as encompassing those who serve the GCRP and the IGBP. More information can be found at the GCDIS Web site.

 

GCIP

Abbreviation for GEWEX Continental-Scale International Project, a multifaceted group of activities designed primarily to improve scientific understanding and the ability to model, for climate prediction purposes, the coupling between the atmosphere and the land surface on a continental scale. GCIP is examining the energy budget and hydrological cycle of the Mississippi River watershed. See the GCIP Web site for further information, including volumes I, II, and III of the GCIP Implementation Plan.

 

GCM

See general circulation model.

 

GCMD

Acronym for Global Change Master Directory, an electronic information resource operated at NSSDC, providing brief information about space and earth science data and data sets. Free, online access allows users to identify relevant data sets and their location, and also allows direct connection to certain specific data centers. See the GCMD Web site.

 

GCOS

Acronym for the Global Climate Observing System, a global observing program planned jointly by ICSU, WMO, UNEP, and IOC of UNESCO. It was established to provide the observations needed to meet the scientific requirements for monitoring the climate, detecting climate change, and for predicting climate variations and change. A Joint Scientific and Technical Committee (JSTC) and a Joint Planning Office (JPO) were set up to develop the plans and strategy for implementation of the system. See the GCOS Web site for more information.

 

GCPS

Acronym for Global Climate Perspectives System, a joint project between two NOAA laboratories (the NCDC and the CDC of the ERL) to study the existence and magnitude of climate changes on a global scale, create high-quality global climate reference datasets and provide access to them, and to crate a set of computer tools to aid in climate research. See the GCPS Web site.

 

GCRI

Abbreviation for the U.S. Greenhouse Climate Response Index, a means of possible early detection and monitoring of anticipated greenhouse-induced climate change in the U.S. It is calculated as the arithmetic average of four indicators:

1. The percent of the U.S. with much above normal minimum temperatures.
2. The percent of the U.S. with much above normal precipitation during the months October through April (the cold season).
3. The percent of the U.S. in extreme or severe drought during the months May through September (the warm season).
4. The percent of the U.S. with a much greater than normal proportion of precipitation derived from extreme 1-day precipitation events (exceeding 2 inches or 50.8 mm).

Much above and below normal are defined as falling within the highest and lowest tenth percentile of the local, long-term record. The GCRI has averaged 12.2% since 1976 (where the expected value for any given year is 10%), whichis 2.8% above the average from previous years in the century although not large or consistent enough to be rejected the statistical possibility that this increase is still a feature of a stable climate. See Karl et al. (1995) and Karl et al. (1996).

 

GCRIO

Acronym for Global Change Research Information Office, established under the GC Research Act of 1990 (Public Law 101-606) to provide United States generated scientific research information in the area of global change to foreign governments, businesses and institutions, and citizens of foreign countries. More information can be found at the GCRIO Web site.

 

GCRP

Abbreviation for Global Change Research Program.

 

GCSS

Abbreviation for the GEWEX Cloud System Study, a project to develop better parameterizations of cloud systems for climate models by an improved understanding of the physical processes at work within various types of cloud systems. More See Browning (1993), GEWEX Cloud System Science Team (1993) and the GCSS Web site.

 

GCTE

Abbreviation for Global Change and Terrestrial Ecosystems, an IGBP project to develop fundamental knowledge of the responses of terrestrial ecosystems to the forces of global change. See the GCTE Web site.

 

GEBA

Acronym for the Global Energy Balance Archive, a database developed at the Swiss Federal Institute of Technology for the worldwide instrumentally measured energy fluxes at the Earth's surface. See Ohmura et al. (1989) and the GEBA Web site.

 

GEBCO

Acronym for GEneral Bathymetric Chart of the Oceans, a map series established by Prince Albert I of Monaco in 1903. This is at present an activity of the IOC. The GEBCO Digital Atlas is now available on CD-ROM.

 

Gelbstoff

Dissolved material in sea water that is resistant to bacterial attack. Its name comes from the yellow color it imparts to the water. Brown algae, the principal algae group growing in coastal waters of temperature and higher latitudes, excrete phenolic compounds. These polyphenols are converted into a brown polymer by secondary reactions with carbohydrates and proteins of algal origin. The properties of the resulting substance are identical with Gelbstoff. Its concentration in sea water is around 1 mg/l and it is removed mainly by precipitation since its phenolic nature renders it resistant to bacterial attack. This is also known as yellow substance or gilvin. See Riley and Chester (1971).

 

GEM

Acronym for the General Ecosystem Model. See Rastetter et al. (1991).

 

GEMS

Acronym for Global Environment Monitoring System.

 

genetic strategy

A unifying concept in ecology defined as a grouping of similar or analogous genetic characteristics which occur widely among species or populations and cause them to exhibit similarities in ecology. See Grime (1979).

 

genetics

More later.

 

GENIE

Acronym for Global Environmental Network for Information Exchange, a project to provide a user-sympathetic system for locating and accessing relevant information on global environmental change. See the GENIE Web site.

 

geodesy

The science concerned with the study of the shape and size of the earth in the geometrical sense and with the study of certain physical phenomena, such as gravity, in seeking explanation of fine irregularities in the earth's shape, and as such in inextricably linked with surveying and cartography.

 

geological oceanography

More later. Compare to biological, chemical and physical oceanography.

 

geoid

A hypothetical, global, and continuous sea-level surface perpendicular to the direction of gravity at all points.

 

GEOSCOPE

Abbreviation for the Interactive Global Change Encyclopedia, a project to demonstrate that satellite data and other geographic information can be of vital importance in monitoring the global environment. See the GEOSCOPE Web site.

 

GEOSECS

Acronym for Geochemical Ocean Sections Study.

 

general circulation model

Generally a three-dimensional time-dependent model of the atmosphere and/or ocean circulation. The solution to a set of mathematical equations governing the motions of a layer of fluid on a spherical planet is numerically approximated on a three-dimensional discrete grid of points to obtain temperatures, velocities, rainfall, pressure and any of several other dependent variables that collectively comprise the state of the climate. Often abbreviated as GCM. See Washington and Parkinson (1986).

 

Generic Mapping Tools

A collection of around 50 UNIX tools that allow the manipulation and graphing of X-Y and X-Y-Z data sets and the output of the results in PostScript format. The data can be manipulated in many different ways and the results can be graphed on a multitude of projections, with just about every imaginable graph attribute amenable to modification. The plotting capabilities include creating basemap plots, plotting coastlines, filled continents, borders and rivers on maps, contouring gridded data, producing images from 2-D data sets, contouring raw data by triangulation, plotting histograms, plotting sector or rose diagrams, and more. Many projections are provided including conic, azimuthal and cylindrical types. A unique feature of GMT is the High-Resolution Coastline Database. This is a five resolution level database of world coastlines, rivers, lakes, and political boundaries. The maps included in the glossary were created using this package. GMT was written for UNIX systems in the C language as is freely available for academic use. See the GMT Web site.

 

GENESIS

The acronym for the Global Environmental and Ecological Simulation of Interactive Systems model developed by Starley Thompson and Dave Pollard at NCAR. It is a heavily modified version of the CCM1 model also developed at NCAR. See Thompson and Pollard (1994) and the GENESIS Web site.

 

geopotential

The potential energy per unit mass of a body due to the Earth's gravitational field as referred to an arbitrary zero reference level. A unit of geopotential is the potential energy acquired by a unit mass on being raised a unit distance in a gravitational field of unit strength.

 

geopotential distance

See dynamic height.

 

geopotential height

See dynamic height.

 

geopotential surface

A surface to which the force of gravity is everywhere perpendicular and equal. No work is necessary for the displacement of mass along a potential surface as long as no other forces act in addition to gravity. This can also be defined as a surface of equal dynamic height below the level of the sea surface, using the ideal sea surface level as a reference surface with the potential value 0. This has also been called a potential surface or a level surface.

 

geopotential thickness

See dynamic height.

 

geostationary orbit

An orbit lying above the Equator in which an artifical satellite moves at the same speed as the Earth rotates. As such it maintains position above the Earth's surface. Such satellites have an altitude of 35,800 km. Satellites in this type of orbit have a continuous view of the full disc of the Earth, although the curvature of the Earth makes it diffucult to gather information for latitudes higher than about 45-50 .

 

geostrophic approximation

The use of the geostrophic wind as an approximation to the actual wind.

 

geostrophic balance

A balance between the Coriolis acceleration and the pressure gradient (divided by the density) in a rotating fluid subject to gravitational restoring forces.

 

geostrophic current

In oceanography, the theoretical current resulting from the balance of the pressure gradient force and the geostrophic force, i.e. the forces associated with horizontal changes in density are compensated by accelerations arising from fluid motion on a rotating Earth. Analogous to the geostrophic wind in meteorology.

 

geostrophic force

A virtual force used to account for the change in direction of the wind relative to the Earth's surface. It results from the Earth's rotation and the Coriolis force.

 

geostrophic turbulence

To be completed.

 

geostrophic wind

In meteorology, the theoretical wind resulting from the balance of the pressure gradient force and the geostrophic force. Analogous to the geostrophic current in oceanography.

 

geosynchronous

An orbit where the period of the satellite is equal to the period of the rotation of the Earth. This is usually used synonymously with geostationary, although the latter has the additional qualities of being circular and in the equatorial plane.

 

Geosynchronous Operational Environmental Satellite

A series of NOAA satellites used for geostationary remote sensing. See the GOES Web site. There is also a SSEC GOES Web site with further edifying information.

 

Gerard barrel

A barrel used to collect water samples in oceanography that holds 250 l.

 

GEWEX

Acronym for the Global Energy and Water Cycle Experiment. Initiated in 1988 by the WCRP to observe and model the hydrologic cycle and energy fluxes in the atmosphere, at the land surface, and in the upper oceans. It is an integrated program of research, observations, and science activities leading to the prediction of global and regional climate change. See the GEWEX Web site.

 

GFDL

Abbreviation for the Geophysical Fluid Dynamics Laboratory established by NOAA. See the GFDL Web site.

 

GGI

Abbreviation for GPS Geoscience Instrument.

 

GHCC

Abbreviation for Global Hydrology and Climate Center.

 

GHCN

Abbreviation for the Global Historical Climatology Network, a comprehensive global baseline climate data site comprised of land surface station observations of temperature, precipitation, and pressure. All data are on a monthly basis with the earliest record dating from 1697. See the GHCN Web site.

 

Gibb's phenomenon

An artifact of attempting to approximate a function or waveform with a discontinuity using a Fourier series or some other global, continuous basis function. The fit is poor in a region near the discontinuity, usually characterized by large oscillations within the region. Increasing the number of components in the approximation decreases the region of poor fit, which theoretically vanishes with an infinite number of components.

 

Gilbert Magnetic Epoch

Reverse polarity time interval extending from 3.3 to 4.5 million years ago. See Bowen (1991).

 

Gilsa Magnetic Event

Short-term normal polarity time interval about 1.6 million years ago within the Matuyama Reverse Epoch. See Bowen (1991).

 

gilvin

See Gelbstoff.

 

GISP

Acronym for Greenland Ice Sheet Project. See the GISP Web site.

 

GISS

An acronym for the Goddard Institute for Space Studies. This is also used to refer to the atmospheric GCM developed and used at that institution. See the GISS Web site.

 

glacial

A time when ice sheets expand and average global climates are cooler and drier than during and interglacial.

 

Glacial Geology and Geomorphology

An electronic journal of the British Geomorphological Research Group. Selected papers are available online at the GGG Web site.

 

glacial period

A time interval during which ice sheets have spread widely across lowlands in the north. During the last million years there have been four major glacial periods. In chronological order they are the Nebraskan, the Kansan, the Saale, and the Warthe-Weischel.

 

glacier zones

A system for classifying zones on glaciers according to ice temperature and the amount of surface melting. The zones are dry snow zone, percolation zone, soaked zone, superimposed ice zone and ablation zone. See Paterson (1969).

 

GLAS

Abbreviation for the Geoscience Laser Altimeter System, an EOS instrument planned for the ALT platforms. It is a nadir-pointed laser altimeter which can measure cloud heights and aerosol vertical structure. See Cohen et al. (1987).

 

glendonite

A pseudomorph after a carbonate (ikaite) that is taken in paleothermometry to reflect cold subaqeuous depositional conditions. Ikaite characteristically grows in cold water sediments that are rich in organic matter, highly alkaline, reducing, and have a high hydrostatic pressure.

 

GLIS

Acronym for Global Land Information System, an interactive computer system developed by the USGS for scientists seeking sources of information about the Earth's land surfaces. See the GLIS Web site.

 

Global Backscatter Experiment

Initiated in 1986, the GLOBE is a cooperative interagency and international research program to characterize the spatial, temporal and spectral variability of atmospheric aerosol backscatter coefficients. See the GLOBE Web site.

 

global change

A transformation which occurs on a world-wide scale (for example, an increase in CO2 in the atmosphere) or exhibits sufficient cumulative effects to have world-wide impact (for example, local species extinction resulting in global loss of biodiversity).

 

global electrical circuit

See atmospheric electrical circuit.

 

Global Energy and Water Cycle Experiment

GEWEX was initiated in 1988 by the WCRP as a program designed to observe and model the hydrologic cycle and energy fluxes in the atmosphere, at the land surface, and in the upper oceans. The International GEWEX Project Office (IGPO) is the focal point for the planning and development of all GEWEX projects and activities. See Chahine (1992a) and Chahine (1992b) and the GEWEX Web site for further information.

 

Global Hydrology and Climate Center

A research center, abbreviated GHCC, whose objective is to address global hydrological processes. See the GHCC Web site.

 

Global Precipitation Climatology Project

A GEWEX-affiliated project, abbreviated GPCP, designed to provide global data sets of area, time-averaged precipitation for a minimum period of 10 years (1986-1995). This data will be produced by merging geostationary and polar-orbiting satellite microwave and infrared data with rain gauge data from more than 6000 stations. More information can be found at the GPCP Web site.

 

global radiative-convective feedback

A feedback loop that links the hydrologic cycle and the ARC. This is a negative feedback that works on the principle that stronger convection leads to more high clouds, which reduces the ARC, further reducing the precipitation rate adn the level of convective activity. See also radiative-dynamical-convective feedback. See Wielicki et al. (1995).

 

Global Runoff Data Center

A GEWEX project, abbreviated GRDC, to compile a global data base of stream flow data for the development and verification of atmospheric and hydrologic models. More information can be obtained at the GRDC Web site.

 

Global Terrestrial Observing System

The GTOS is a global observing program planned jointly by FAO, UNESCO, ICSU, WMO, and UNEP.

 

Global Warming Potential

The GWP is an index of the strength of the radiative forcing induced by greenhouse gases. It is defined in the IPCC Report Shine et al. (1990) as the time-integrated commitment to climate forcing from the instantaneous release of 1 kg of a trace gas expressed relative to that from 1 kg of carbon dioxide.

 

GLOBE

1. Acronym for the Global Backscatter Experiment. 2. Acronym for the Global Land One-kilometer Base Elevation GlobalLandOne project, an international effort to develop a best-available global digital elevation map on a 1-kilometer grid. See the GLOBE Web site. 3. Acronym for the Global Learning and Observations to Benefit the Environment program, a national and internationalhands-on environmental science and education program. It uses scientific instruments and state-of-the-art technology to make science relevant to todays K-12 students. See the GLOBE Web site.

 

GLOBEC

Acronym for Global Ocean Ecosystem Dynamics, a component of the IGBP developed and sponsored by SCOR, the IOC, the ICES, and PICES. Its goal is advance our understanding of the structure and functioning of the global ocean ecosystem, its major subsystems, and its response to physical forcing to where we can develop and capability to forecast the marine upper trophic system response to scenarios of global change. GLOBEC concentrates on zooplankton population dynamics and its response to physical forcing in pursuit of this goal. See the GLOBEC Web site or the U.S. GLOBEC Web site.

 

globigerina ooze

A type of calcareous ooze composed of the shells of unicellular creatures called globigerina that live in the waters of warmer ocean regions. These oozes are seldom found above 5000 m depth and cover about 35% of the surface of the sea floor. See Neumann and Pierson (1966) and Tchernia (1980).

 

Gloger's Rule

An ecogeographical rule that states that races of warm-blooded animals in warmer regions are more darkly colored than races in colder or drier regions. It was established by Contantin Wilhelm Lambert Gloger in 1833.

 

GLOSS

Acronym for the Global Sea Level Observing System, an IOC-coordinated project for the establishment of a strategic gloval core network of about 300 tide gauges around the world for long term climate change and oceanographic sea level monitoring. These gauges are spaced about 1000 km apart along coastlines and on oceanic islands and provide hourly-resolution standardized sea level data. See the GLOSS Web page.

 

GLRS

Abbreviation for Geoscience Laser Ranging System.

 

glycophytes

Plants intolerant to salinity.

 

glycohalophytes

Plants able to withstand moderate salinity, i.e. adapted to high osmotic potentials in soil water.

 

GMCC

Abbreviation for Geophysical Monitoring of Climate Change.

 

GMP

Abbreviation for Gulf of Mexico Program.

 

GMT

1. Abbreviation for Greenwich Mean Time. 2. Abbreviation for Generic Mapping Tools.