Acronym for European North Atlantic Margin, a series of projects
to quantify and model large-scale sedimentary processes and
fluxes in the named area. See the
ENAM Web site.
A low-lying region that is free of ice during a
glacial stage. Constrast with
- energy balance model
class of climate models (abbreviated as EBM) that focuses on the
required balance between incoming and outgoing radiation at the top
of the atmosphere. EBMs are solely thermodynamic and include no
dynamics or moisture processes and as such calculate only one
the temperature. Nonetheless, the temperature
fields calculated using 2-D EBMs agree well with both observations
and fields calculated using more complex
general circulation model.
See Crowley and North (1991) and
North et al. (1981).
Acronym for El Niño Monitoring Center.
See Eastern North Pacific Central Water.
Acronym for the European Network for Research in Global Change, the
objective of which is to pursue a major coherent European
contribution to international actions on global change research.
See the ENRICH Web site.
The collection of all possible realizations
of a stochastic process.
See El Nino/Southern Oscillation.
This is defined as half of the area-mean
vorticity squared in a fluid,
mathematically expressed by
where A is the area over which the calculation is being made
and the vorticity.
The relation between vorticity and enstrophy is similar to that
between velocity and kinetic energy, and the enstrophy budget
is used in the study of large-scale motions in the ocean and
atmosphere as an alternative to the more cumbersome vorticity
See Wiin-Nielsen and Chen (1993).
The heat content per unit mass of a substance measured as the
internal energy plus the product of its volume and pressure.
In the atmosphere this is the sum of the
latent heat and superheat of the
vapor above the saturation or
- entity cloud
An abstraction used in the parameterization of clouds in large-scale
numerical models. This is the physical entity consisting of a part of
the condensate and occupying a certain volume of air that is often only
a fraction of a grid volume.
See Sundqvist (1993).
- entrainment interfacial layer
The sharp transition
zone between the
planetary boundary layer
and the free atmosphere in the
interfacial region between cloud and no-cloud in the atmosphere.
The EIL can evince a temperature change of C over less
than 5 m. The has also been called the
entrainment zone (EZ).
See Kraus and Businger (1994).
- entrainment zone
Another name for the
entrainment interfacial layer.
Acronym for Environmental Treaties and Resource Indicators, a service
that provides online searching of a database that integrates
information about environmental treaties with national
ENTRI Web site.
- Environmental Research Laboratories (ERL)
A division of the NESDIS branch of
NOAA whose mission is to conduct an
integrated program of fundamental research, related technology
development, and services to improve understanding and prediction
of the geophysical environment consisting of the oceans and inland
waters, lower and upper atmosphere, the space environment, and
the earth. The ERL is composed of major units throughout the
United States, including the
Aeronomy Laboratory (AL), the
Atlantic Oceanographic and Meteorological Laboratory (AOML), the
Air Resources Laboratory (ARL), the
Climate Diagnostics Center (CDC), the
Climate Monitoring and Diagnostics Laboratory (CMDL), the
Environmental Technology Laboratory (ETL), the
Forecast Systems Laboratory (FSL), the
Geophysical Fluid Dynamics Laboratory (GFDL), the
Great Lakes Environmental Research Laboratory (GLERL), the
National Severe Storms Laboratory (NSSL), the
Pacific Marine Environmental Laboratory (PMEL), and the
Space Environment Laboratory (SEL).
The ERL also establishes formal collaborative research agreements
with participating universities to form the Joint Institutes, which
combine the resources of research-oriented universities and ERL to
develop centers of excellence in research on the earth's oceans,
inland waters, the atmosphere, and the solar-terrestrial
environment. The eight current Joint Institutes are the
Cooperative Institute for Arctic Research (CIFAR), the
Cooperative Institute for Limnology and Ecosystems
Research (CILER), the
Cooperative Institute for Marine and Atmospheric
Studies (CIMAS), the
Cooperative Institute for Mesoscale Meteorological
Studies (CIMMS), the
Cooperative Institute for Research in the Atmosphere (CIRA), the
Cooperative Institute for Research in Environmental Sciences, the
Joint Institute for Marine and Atmospheric Research (JIMAR), and the
Joint Institute for the Study of the Atmosphere and Ocean (JISAO).
See the ERL Web site.
- Environmental Technology Laboratory (ETL)
A part of the NOAA ERL
network which supports NOAA's environmental monitoring and stewardship
charter by performing oceanic and atmospheric research and developing
new remote sensing systems. ETL comrises five divisions which
study ocean remote sensing, atmospheric lidar, radar meteorology
and oceanography, meteorological applications and assessment,
and system demonstration and integration.
ETL Web site.
The second of five epochs in
the Tertiary period, lasting from 57.8 to 36.6 Ma.
It is preceded by the Paleocene epoch
and followed by the Oligocene epoch.
Acronym for empirical orthogonal function.
Earth Orientation Parameters.
Acronym for EURECA Occultation Radiometer, an instrument used
to study water vapor in the upper atmosphere in the region of
Abbreviation for Earth Observation Research Center, a research
center started in April 1995 as the new center for the
National Space Development Agency of Japan (NASDA).
NASDA Web site.
Acronym for Earth Observing System,
the suite of satellite sensors to be launched and managed by
NASA under the Mission to Planet Earth Program in support of
the U.S. Interagency Global Change Research Program (GCRP).
This network of polar-orbiting and low-inclination
satellites will provide global observations of the land surface,
biosphere, solid Earth, atmospheres and oceans for a
minimum of 15 years. See the
EOS Web site.
Acronym for EOS Amazon Project.
Acronym for Earth Observing System Data and Information System,
the NASA infrastructure of seven DAACs
which receive, process, archive, manage and
distribute EOS data products among EOS investigators.
EOSDIS Web site.
Acronym for the Earth Observing System Interdisciplinary
Science project, a NASA project to improve diagnosis of global
changes through the understanding of the coupled ocean-atmosphere
system. The objectives are to improve existing and develop new
methodologies for estimating global ocean-atmosphere fluxes in
momentum, energy, water and carbon dioxide, to study the changes
in the transport and storage of heat, water, and greehouse gases
by the ocean in response to surface forcing, and to understand
the energy and hydrologic balances of the atmosphere and their
relation with ocean surface fluxes. See the
EOSIS Web site.
Abbreviation for Earth Observing Scanning Polarimeter, an
EOS instrument planned for the AM2 and AM3
satellite platforms. It is a cross track scanning polarimeter
which globally maps radiance and linear polarization of reflected
and scattered sunlight for 12 spectral bands from 0.41 to 2.25
micrometers. It will provide global aerosol distribution and
cloud properties such as optical thickness and phase.
Abbreviation for EOS Space Measurement System.
Acronym for Earth Observation World Information Centre.
Abbreviation for European Paleoclimate and Man since the last
Glaciation, a program to reconstruct the development of European
climate since the last glaciation and interpret it in terms
of natural and human influences.
EPC Web site.
- epeiric sea
A shallow inland sea with limited connection to the open
ocean and having depths less than 250 meters. Compare to
epicontinental sea and
Acronym for Equatorial Pacific Information Collection.
Acronym for European Project for Ice Coring in Antarctica.
EPICA Web site.
- epicontinental sea
A shallow sea on a wide portion of a
or in the interior of a continent. The former type is
also known as a shelf sea. Compare to
epeiric sea and
One of two categories into which benthic
marine animals are sometimes divided according to their
differing ecological characteristics, the other category being
the infauna. The epifauna comprises
all animals living upon or associated with rocks, stones, shells,
piling, and vegetation, i.e. those that sit or crawl on a
See Thorson (1957).
The layer of water above the
thermocline in a fresh water
lake, as opposed to the
This is equivalent to the mixed layer
in the ocean.
- epipelagic zone
One of five vertical ecological zones into which the
deep sea is sometimes divided.
The epipelagic zone extends from the surface downward as
far as sunlight penetrates during the day. It is a very thin
layer, less than 100 meters thick in the eastern parts of
the oceans in regions of upwelling and high productivity and
up to 200 meters thick in clear subtropical areas. The endemic
species of this zone either do not migrate or perform only
limited vertical migrations, although there are many animals
that do invade the epipelagic zone from deeper layers during
the night or pass their early development stages in the
photic zone. The epipelagic zone overlies the
See Bruun (1957).
Acronym for Eastern Pacific Oceanic Conference.
Acronym for the NOAA Equatorial Pacific Ocean
Climate Studies program. The goal of EPOCS was to obtain the
requisite knowledge of the underlying physical and
thermodynamic processes in the equatorial Pacific to enable
the anticipation, planning, and alleviation of adverse social
and economic impacts due to short-term climate variations.
Acronym for European Polar Orbiting Platform.
Acronym for Equatorial Pacific Project, a JGOFS
- equable climates
This refers to hypothesized past warm climates lacking
in extreme variations, although the viability of the concept
has been called into question in light of recent modeling
results concerning supercontinents.
See Crowley and North (1991) section 11.2.7 and
the references therein.
Acronym for Equatorial Atlantic Survey.
Acronym for Cooperative Survey of the Pacific Equatorial
Zone, a joint France/Japan/USA project.
Acronym for International Study of the Equatorial Segment of
the Mid-Atlantic Ridge.
- equation of mass continuity
An equation stating that because the mass of a fluid parcel is
constant, the density must decrease/increase if the flow
diverges/converges. This is mathematically expressed by
where is the fluid density and v the vector
See Dutton (1986).
- equatorial beta plane
An approximation for oceanic and atmospheric motions near the
equator where the substitutions
cos are made into the governing equations of
motion. In this approximation, beta is a constant given by
where is the rotation rate of the earth and
r its radius, and f is given by
where is distance northward from the equator.
See Hendershott (1981), p. 304 and
Gill (1982), p. 434.
- Equatorial Countercurrent
In physical oceanography, a subsurface eastward flow that is about
100-200 m thick and 200-300 km wide. It is centered approximately
on the equator, and its core lies just beneath the base of
the mixed layer in the top of the
equatorial thermocline. Such a
current is found in all three oceans, although it appears to
be a seasonal phenomenon in the Indian Ocean.
See Leetmaa et al. (1981).
- Equatorial Intermediate Current
A westward flowing equatorial current in the Pacific Ocean
the underlies the eastward-flowing
Equatorial Undercurrent (EUC).
See Delcroix and Henin (1988).
- equatorial radius of deformation
A form of the
Rossby radius of deformation applicable to wave motions near and
at the equator. It is defined as
where c is the gravity wave speed, i.e.
where H is the depth (or equivalent depth).
This radius is about 2000 km (c = 200 m/s) for barotropic
waves in the ocean, making it marginally applicable for use
with the equatorial beta plane concept. The approximation is much more
valid for the case of baroclinic waves where, for typical
atmosphere (20-80 m/s) and ocean (0.5-3.0 m/s) values of c,
the equatorial deformation radius is, respectively,
650-1300 km and 100-250 km.
- equatorial trough
A region of lower pressure located between the subtropical highs
on each side of the equator.
Within this zone the trade wind
airstreams from either hemisphere meet causing ascending
motion and large amounts of precipitation. It constitutes
the equatorward, ascending portions of the Hadley mean
meridional circulation cells of both hemispheres.
Energetically this results in an import of water vapor concentrated
in the trade wind layer and an export of geopotential energy and
sensible heat in th eupper troposphere. This results in a net
atmospheric heat export from the trough zone to the higher
This region, commonly called the doldrums, is centered near
S in January and N in July.
Its migration between these extremes
influences the seasonal distribution of cloudiness
and rainfall and the formation of tropical storms, and its
annual mean position is known as the
- Equatorial Undercurrent
In physical oceanography, a subsurface eastward flow centered approximately
on the equator whose core lies just beneath the base of
the mixed layer in the top of the
equatorial thermocline. The flow
generally ranges from 100-200 m thick and 200-300 km wide.
Such a current is found in all three oceans, although it appears to
be a seasonal phenomenon in the Indian Ocean.
In the Atlantic
its core is around 100 m deep with speeds exceeding 1.2 m/s and transports
up to 15 Sv. It alternates between extreme positions 90 km on either
side of the Equator on a 2-3 week time scale with speed and transport
fluctuating between the previous figures and 0.6 m/s and 4 Sv.
In the Pacific it has a width of 400 km, a thickness of only 200 m,
and typical velocities of 1.5 m/s, with the core depth
ranging from 200m in the west to 40 m in the east. The details
are much more complicated and less well known for the Indian Ocean,
although it appears to be present primarily during the northeast
monsoon. This is also known as the Cromwell Current in the
Pacific Ocean after Cromwell et al. (1954).
The dynamical explanation for a an undercurrent has an appealing
qualitative explanation, i.e. fluid converging towards the equator
conserves absolute vorticity. As a result, relative vorticity has
to increase to make up for the vanishing of planetary vorticity
there, with this providing a source of eastward momentum
to drive the undercurrent. The balance of forces at the
equator reduces to
where p is the pressure (baroclinic), x the coordinate along
the equator, the momentum diffusion coefficient, z the
vertical coordinate, and u the along equator velocity component.
This is a linear equation, and although the addition of nonlinearities
has brought model results and observations into closer concordance,
it is thought that they are not essential for maintaining the
undercurrent and serve only to modify the linear dynamics.
The unsteady flow represented by the dynamics of equatorial waves
has also been postulated as an explanation for the observe
time-varying characteristics of the undercurrent.
See Philander (1973), Philander (1980),
Leetmaa et al. (1981), Peterson and Stramma (1991) and
Tomczak and Godfrey (1994).
- equatorially trapped gravity wave
- equatorially trapped Kelvin wave
An equatorially trapped wave
similar in character to coastally trapped
The motion is unidirectional and parallel to the equator
everywhere, and in each vertical plane parallel to the equator
the motion is the same as for a nonrotating fluid.
A required geostrophic balance
between the east-west velocity and the north-south pressure
gradient leads to solutions that decay away from either
side of the equator on a length scale called the
equatorial radius of deformation.
These dispersionless waves propagate eastward at the same speed as
they would in a nonrotating fluid, with the dispersion relation
being . The magnitude of c for the first
baroclinic mode for typical ocean values is around 2.8 m/s,
which would take a Kelvin wave across the Pacific in about
See Gill (1982).
- equatorially trapped Poincare wave
See equatorially trapped gravity wave.
- equatorially trapped Rossby wave
- equatorially trapped wave
A wave that is confined to propagate on and near the equator due
to the local waveguide properties. The waveguide is caused by
the vanishing of at the equator. This means that the
conditions for geostrophic balance
theoretically fail there, although practically any wave motion
having a finite expanse across the equator will feel the
Coriolis force on either
side. This will serve to turn that motion back towards the
equator on either side, thus serving as a trap or a waveguide
for motions there.
See Gill (1982).
- Equilant cruises
A series of research cruises in 1965-1966 that performed
tightly organized surveys of the tropical Atlantic. Simultaneous
data on temperature, salinity and currents were obtained for
the then little-known area off the west coast of Africa.
These cruises were done with ships from the U.S., the Soviet
Union, France, Brazil and other nations.
See Idyll (1969).
- equilibration time
The time it takes for a system to re-equilibrate after being
subject to a perturbation. This is usually expressed in terms
of an e-folding time. Some typical
equilibration times are: the atmosphere, 11 days; the ocean
mixed layer, 7-8 years; the deep ocean, 300-1000 years;
mountain glaciers, 300 years; ice sheets, 3000 years; the
Earth's mantle, 30 million years.
- equilibrium tide
The hypothetical tide which would exist
if the ocean responded instantly to the tide producing forces
and formed an equilibrium surface. The effects of friction, inertia, and
the irregular distribution of land masses are ignored.
One of the two days in a year (presently about March 21 and Sept. 23) when
there are exactly 12 hours of day and 12 hours of night at all points
on the Earth. The two points on the
where the ecliptic intersects
the celestial equator. At the
vernal equinox the Sun crosses the celestial equator from south to
the north, and at the autumnal equinox from north to south, with the
former being the zero point in celestial coordinate systems.
- equivalent barotropic
An atmospheric state in which the temperature gradients are such that
the isotherms are parallel to the
- equivalent carbon dioxide concentration
For a given amount of a greenhouse gas, the amount of
carbon dioxide that would provide an equivalent forcing.
- equivalent depth
When the solution of a differential equation set (e.g. the equations
of motion for a baroclinic atmosphere or ocean) is approximated using the
normal mode technique, each of the independent
normal or baroclinic mode solutions obtained behaves equivalently
to a homogeneous system with a depth that is called the equivalent
depth. See Gill (1982).
- equivalent potential temperature
In meteorology, the
of an air sample when it is brought adiabatically
to a pressure of 1000 mb. It is a conservative property for both dry
and saturated adiabatic processes.
- equivalent temperature
The temperature that a sample of moist air would attain if all of the
water vapor were condensed and the latent heat
released to raise the temperature of the sample, i.e. the temperature
arrived at isobarically when all the vapor in a sample is condensed.
It is given by
where e is the mixing ratio,
L is the appropriate latent heat,
the specific heat at constant pressure, and p the
Acronym for the Earth Radiation Budget Experiment, the
first multiple-satellite radiation budget experiment, which included
a medium-inclination orbiter to measure diurnal variations and used
a scene-dependent inversion scheme.
See Barkstrom (1984) and the
ERBE Web site for more details.
Acronym for Regional Study of the El Niño Phenomenon, a joint
The unit of work or energy in the cgs system
of units. It is the work done by a force of 1 dyne
in moving its point of application 1 cm in the direction of the
force. Some equivalences are: 1 erg = 10 joules =
10 watt sec.
Acronym for European Marine Research Geographical Information
Service, a project to improve access to spatially referenced
data relating the European and global offshore waters.
It will integrate data on installations, bathymetry, morphology,
oceanography, meteorology, commercial and marine activity from
MARIS Web site.
- ergodic hypothesis
The assumption that a process is statistically
stationary, and therefore ensemble
averaging is equivalent to averaging over time.
See Kagan (1995).
Acronym for the Experiment on Rapidly Intensifying Cyclones Over the
Atlantic project, a study to determine physical mechanisms and proceses
which lead to explosive wintertime storms developing over the
Atlantic Ocean. The planning phase took place during 1987-1988
and the operations phase during 1988-1989.
This is a follow-up to the
GALE experiment. See the
ERICA Web site.
Acronym for the Australian
Environmental Resources Information Network.
ERIN Web site.
Acronym for the
Environmental Research Laboratories.
Acronym for Exact Repeat Mission, a GEOSAT mission to accurately measure and
calculate sea level deviations from the geoid.
See Cheney et al. (1986).
Acronym for Earth Resources Observations System.
- error of representativeness
The spatial spectrum of the atmosphere or ocean shows variance at
all scales, with generally less variance at smaller scales.
The observation network, however, has a finite spacing between
observation stations. If a network has an average spacing of, say,
L between stations, then samples with scales much greater or smaller
will be sample, respectively, very well or very poorly by the network.
For instance, a network with 1000 km spacing will not see a tornado
or thunderstorm with a 10 km characteristic length scale if it is
between stations, but will see it if it overlies a station and, in
addition, will misrepresent it as a larger scale motion. This
is occasionally known as aliasing.
See Daley (1991).
Acronym for the Earth Resources Satellite.
- Ertel potential vorticity
A rigorous formulation of
for any compressible, thermodynamically active, inviscid fluid in
adiabatic flow. The Ertel potential vorticity is defined by
where S is some conservative thermodynamic property of the fluid
(the potential temperature, e.g.), is the angular velocity
of the coordinate system, is the density, and V the velocity
of the fluid relative to the coordinate system.
See Muller (1995).
- Ertel's theorem
A theorem stating that in an incompressible Boussinesq fluid
that is homogeneous and inviscid a quantity called the
potential vorticity is
See Hide (1978).
Abbreviation for European Space Agency. See the
ESA Web site for further information.
Abbreviation for the NASA/GSFC's Earth Science Directorate, whose
mission is to provide leadership in achieving improved observations
and understanding of global Earth systems and trends through the
development and effective utilization of space technologies.
See the ESD Web site for further information.
Abbreviation for European Science Foundation. See the
ESF Web site.
Abbreviation for electronic scanning microwave radiometer.
Acronym for European SubPolar Ocean Program, whose overall objective
is to understand the role played by sea ice in the energetics of the
Greenland Sea system as a whole as well as in the specific
ice-ocean interactions involved in the process of deep winter
convection and its attendant sequestration of carbon dioxide.
The project began in July 1993 and will continue for three years.
ESOP Web site.
Acronym for European Stress Physiology and Climate Experiment.
See Eastern South Pacific Central Water.
Acronym for European Space Research Institute, an establishment of
ESA. Its main activities are centered on the
acquisition, archiving and dissemination of data from Earth
Observation missions, in particular ERS-1. See the
ESRIN Web site for further
Abbreviation for the Earth and Space Science project, an effort to
employ advanced computers to further understanding of and ability
to predict the dynamically interacting physical, chemical, and
biological processes that drive these systems. It is an integral
component of the NASA HPCC program, and more
information can be found at the
ESS Web site.
Abbreviation for the Earth System Science Center, a research
institute at Penn State that coordinates research related to
the global water cycle, biogeochemical cycles, Earth system
history, and human impacts on the Earth system. See the
ESSC Web site.
Abbreviation for Earth System Science Education, a project that links
faculty at over 20 universities with one another and with NASA
scientists to accelerate the development of undergraduate
curricula in earth system science.
The project objectives were to establish such a national academic
forum and also to expand the interdisciplinary interests and number
of future scientists who elect to pursue earth science research
professionally. See the
ESSE Web site.
Acronym for Electronically Scanned Thinned Array Radiometer,
a proposed remote sensing technique for monitoring the
large scale distribution of surface salinity. It depends on
the influence of salinity on microwave emissions, strongest
at 1.4 GHz. Since temperature has a larger effect, high
accuracy temperature measurements must also be made using
another band at either 2.65 or 5.0 GHz. This yields a
salinity accuracy of 0.05 parts per thousand, although this
can be achieved only via long time (30 days) and space
(100 km) averaging. A resolution of 10 km would degrade
salinity measurement accuracy to 2 parts per thousand.
See Swift (1993) and Schmitt (1995).
- estuarine Richardson number
A form of the Richardson number
that gauges the relative effects of stratification and mixing
in estuaries. It is given by
where is the RMS tidal velocity, W the channel width,
the difference in density between river and ocean water,
the average density, g gravitational acceleration and
the fresh water discharge rate.
If R is large the estuary will be strongly stratified the
flow dominated by density currents, and if it is small
the estuary will be well mixed and density effects can probably
be neglected. There is also a modified version of this in
which is replaced by the shear velocity to include
the effect of varying bottom friction.
See Fischer et al. (1979).
A semi-enclosed body of water having a free connection with the
open sea and within which sea water is measurably diluted with
fresh water derived from land drainage. The term has traditionally
been applied to the lower reaches of rivers into which sea water
intrudes and mixes with fresh water as well as to bays, inlets,
gulfs and sounds into which several rivers might empty and in which
the mixing of fresh and salt water occurs.
Distinctions between estuaries are usually made based on the prevailing
physical oceanographic conditions (principally the salinity distribution)
which are governed by the geometry of the estuary, the magnitude of
fresh water flow into the estuary, and the magnitude and extent
of the tidal motion. The four principal categories into which
estuaries are divided using these criteria are
arrested salt wedge and
fjord entrainment estuaries,
although a single estuary can vary seasonally from one type to
See Emery and Stevenson (1957) and Officer (1976).
A French research program that took place from 1993 until
April-May 1996. It was a program in the western Equatorial
Atlantic Ocean wherein hydrographic cruises with tracers were
conducted along three meridional and one zonal section off
Northeast South America in the region west of 35 W and
south of 7.5 N. This was followed up by the
Abbreviation for Expert Tsunami Database for the Pacific.
A Greek term for winds that blow at times in summer (May to
September) from a direction ranging from northeast to northwest in
the eastern Mediterranean. In Turkey these winds are known as
Acronym for European Tracer Experiment, a joint project of CEC,
WMO and IAEA.
Abbreviation for European Tropical Forest Research Network.
Environmental Technology Laboratory.
A five-minute resolution database of land elevations and ocean
National Geophysical Data Center (NGDC)
interactive online ETOPO5 database with which
portions of the database can be selected and downloaded.
Abbreviaton for Eastern Tropical Pacific.
Abbreviation for Eurasian Oscillation.
Acronym for the Eurasian Basin Experiment.
Acronym for European Cirrus Research Experiment.
Descriptive of organisms with cells having a distinct nucleus.
This includes all protists, fungi, plants and animals.
- Euler equations
- Eulerian mean circulation
In oceanography, the time-averaged flow field in a fixed coordinate
system. This can be remarkably different from the
synoptic mean circulation.
See Schmitz and McCartney (1993).
- Eulerian velocity
That velocity which would be measured by a current meter at a fixed
point. Compare and contrast to
Lagrangian velocity and
Abbreviation for European Meteorological Satellite Organization,
an intergovernmental agency which provides operational
meteorological data for its member states.
- euphotic zone
In the ocean, the sunlit layer consisting of the upper 100 m or so
in which most of the
takes place. The depth varies geographically and seasonally
and can range from a few meters in turbid waters near the
shore to 120 m in the
It is a zone
with sharp gradients in illumination, temperature and salinity, and
is the upper of three vertical zones that comprise the
pelagic part of the ocean, the other two
being the middle mesopelagic and the
lower bathypelagic zones. It is also
known as the photic zone.
- Eurafrican Mediterranean Water
In physical oceanography, a
water mass that
leaves the Strait of Gibraltar with
a temperature of about 13.5 C and a salinity of
37.8 but is transformed by mixing to a temperature and
salinity of 11-12 C and 36.0-36.2 within 250 km.
From there it spreads isopycnally across the ocean, mixing
gradually with the water above and below.
A MAST program for the observation and modeling
of the large-scale movement of the
Mediterranean Water (MW) and
Labrador Sea Water (LSW) in the
eastern North Atlantic Ocean.
The principal objectives including determining the mean circulation
of the MW and LSW in the intergyre region of the eastern North
Atlantic and discovering if there is a stokes drift or eddy
mixing of the MW and LSW. A large part
of EUROFLOAT will be a lagrangian circulation experiment
wherein subsurface neutrally buoyant floats
will be used to observe the movement of deep water masses over a
period of 3 years.
The ARCANE project is a companion study
EUROFLOAT Web site.
A program to support the European component of the
GOOS. It exists to maximize the benefits
to Europe from operational oceanography and the aims include
indentifying European priorities for operational
oceanography, promoting the development of various systems
(i.e. scientific, technological, and computer) for operational
oceanography, and establishing methods of routine collaboration
between European national and multi-national agencies for the
conduct of operational oceanography.
EuroGOOS Web site.
- European Geophysical Society (EGS)
A society founded in 1971 to promote the earth and space sciences
on and multidisciplinary, pan-European, international level.
The scientific journals which the EGS either runs or participates
in include ``Annales Geophysicae,'' ``Climate Dynamics,''
``Geophysical Journal International,'' ``Journal of Atmospheric
Chemistry,'' ``Journal of Geodynamics,'' ``Nonlinear Processes in
Geophysics,'' ``Physics and Chemistry of the Earth,''
``Planetary and Space Science,'' ``Surveys in Geophysics,''
EGS Web site.
Acronym for European Experiment on Transport and Transformation of
Environmentally Relevant Trace Constituents in the Troposphere
Descriptive of global sea level
variations due to absolute changes in the quantity of seawater,
the most recent significant examples of which have been
caused by the waxing and waning of continental ice sheets during
A situation in which the increased availability of nutrients such
as nitrate and phosphate (e.g. from the use of agricultural
fertilizers and the combustion of fossil fuels) stimulates the
growth of plants such that the oxygen content is depleted and
carbon sequestered. It is hypothesized that this might serve
as a negative feedback to an increase
in atmospheric CO2.
Abbreviation for extreme ultraviolet.
- evaporative cooling
A phenomenon wherein the evaporation of water from saturated
air (when, for example, it mixes with drier air) cools the
air due to the absorption of
A water-soluble mineral (such as halite, gypsum, or anhydrite), or
a rock composed of such minerals, precipitated out of saline water
bodies such as salt lakes.
Evaporation plus the water discharged into the atmosphere by plant
transpiration, i.e. the removal of
water from the surface to the air with an accompanying change in
phase from the liquid to the vapor form.
- evolutionary biology
The irradiance from below a unit area, below
being relative to the direction of the original radiation source.
- Exner function
The Exner function is given by
where p is the atmospheric pressure, a reference
pressure, and the ratio of the
of a perfect gas. It is used in studies of
compressible adiabatic flow.
The outermost layer of the atmosphere. It has no clear outer boundary
but merges imperceptibly with interstellar space, and its lower
boundary is almost as indistinct at an altitude of about 370 miles
between the exosphere and the ionosphere.
It is mainly composed of
hydrogen and helium, with a small quantity of molecular oxygen up
to around 370 miles. Helium gradually vanishes with increasing
altitude to about 1,500 miles, after which the exosphere is almost
entirely comprised of hydrogen.
- explicit scheme
In numerical modeling, an integration algorithm that temporally advances
an approximate solution via discrete steps using only information
from previous time steps. These are computationally simpler than
implicit schemes but require shorter
time stepping intervals.
See Kowalik and Murty (1993).
- export flux
See biological pump.
- export production
In biological oceanography, the loss rate of organic carbon (and
nitrogen) from the surface ocean layer to the ocean interior.
Acronym for the Experiment for Regional Sources and Sinks of
Oxidants, a component of GTCP
implemented to quantify fluxes of numerous chemical
species over a range of spatial scales from the individual leaf,
branch, and soil surface up to landscape and regional scales. See the
EXPRESSO Web site.
- extensive parameter
A determining parameter of a system that is proportional to the
size and mass of the system, e.g. volume, internal energy,
enthalpy and entropy, as opposed to an
- extinction coefficient
A coefficient measuring the rate of extinction, or diminution,
with distance of transmitted light in sea water. It is the
attenuation coefficient for visible radiation.
- extinction event
A general name given to any of the several mass extinctions
of taxa found in the data record of Earth history.
- extreme events
In the context of climate change,
extreme events are infrequent meteorological events that surpass
a certain threshold. Observations indicate no compelling
evidence that extreme weather events or climate variability
has increased globally in the 20th century, although the
available data is poor and intermittent in many cases and
therefore the analyses aren't comprehensive. There is some
evidence for regional changes in extremes and climate variability,
although some points to greater and some to lower variability.
There is no clear picture from the data as yet.
The present generation of GCMs lack
the resolution needed to accurately model these synoptic and
short time scale events, and the integrations are also usually
too short in duration to permit statistical analysis of local
weather extremes. However, using other lines of evidence
such as physical reasoning, inferring extreme events from
larger patterns like mid-latitude storm tracks, and results from the
occasional high resolution model experiment, some tentative
assessments can be made. Small changes in either the mean climate
or its variability may produce relatively large changes
in the frequency of extreme events, with a change in the
variability having a stronger effect than a comparable change
in the mean. A general warming trend can tend to increase
extreme high temperatures as well as decrease the number
of winter days with extreme low temperatures. Daily temperature
variability may decrease with increased CO2 in some regions,
with increased precipitation variability over a few areas.
Lastly, some results suggest that a warmer climate will
lead to an increase in precipitation intensity and therefore
more extreme events, with more frequent and severe drought
periods seen in some cases.
See Houghton and Filho (1995).