- Abbreviation for
East Australian Current.
- Abbreviation for
East Arabian Current.
- Abbreviation for
Eastern Atlantic Experiment.
- Abbreviation for East Asian Seas Action Program.
- East Africa Coast Current
- See Somali Current.
- East Arabian Current
- A strong northeastward flowing current along the Saudi
Arabian coast. It is part of the monsoonal circulation
in the area and as such exists from about April through
October, being fully established by mid-May with
velocities ranging form 0.5-0.8 m/s. It is also part
of a strong coastal upwelling system during those months
when it flows strongest.
- East Arabian Sea Water
- See Bay of Bengal Water.
- East Auckland Current
- The continuation of the
East Australian Current
east of New Zealand. It forms and is part of an anticyclonic
eddy near 37 S off of East Cape. This eddy is found in
the same location throughout the years and as such is thought
to be topographically controlled. The further extension of
this current has a bimodal nature that changes seasonally.
During the summer most of its transport continues along the
New Zealand coast all the way to Chatham Rise as the
East Cape Current. In the winter part of it separates from
the shelf and continues as a zonal flow into the open
ocean, forming a temperature front near 29 S that
is distinguishable from another shallow front near
25 S called the Tropical Front, the northern limit of
eastward flow in the subtropical gyre.
See Tomczak and Godfrey (1994).
- East Australian Current
- The western boundary current of the southern hemisphere in the
Pacific Ocean. It is the weakest of the world's boundary
currents, carrying about 15 Sv in the annual mean near
30 N, yet is also associated with strong current
instabilities. The relative weakness is due mostly to
the flow through the
Australasian Mediterranean Sea and the instabilities probably result
from the current following the coast and then suddenly
separating somewhere near 34 S to follow the
east coast of New Zealand (where it is known as the
East Auckland Current).
It is stronger and reaches further
inshore during the summer, with flow speeds reaching
1 m/s during the summer, and the maximum transport has been
estimated at around 30 Sv (although the intermittent nature
of the current makes such estimates somewhat suspect).
The path it follows from Australia to New Zealand is called
the Tasman Front, which separates the warmer waters of the
Coral Sea from the colder waters of the Tasman Sea. This
front develops meanders which travel westward, impinge upon
the Australian coast, and ultimately separate from the current
and form eddies. About 3 eddies are spawned per year (with
4-8 existing at any one time in recognizable form) with most
being anticyclonic or warm core eddies since the meander
closest to the coast always extends to the south.
The meandering and eddy-shedding behavior of the current
combined with its weak flow sometimes make it difficult to even
distinguish it as a current, and the location of the Tasman
Front can be meaningfully defined only in statistical terms.
The pronounced seasonal cycle is described
by Ridgway and Godfrey (1997):
Maps of the
annual-frequency component of the surface and depth-integrated
steric heights ( h and P) show the development and progression of
the EAC flow regime through a complete seasonal cycle. The EAC
has a strong seasonal cycle from 25°S to 45°S, with strongest
southward flow in austral summer. The seasonal cycle in surface
flow over the continental shelf is documented by two independent
methods, geostrophically, using cross shelf sea level gradients
derived from coastal tide gauge data and steric heights at the
continental shelf edge, and directly from merchant ship
observations. The two estimates are in good agreement.
The seasonal cycle in
the EAC is more pronounced than in other mid-latitude
western boundary currents for which data are
available. At 28°S, the strength of
the total Tasman Sea transport (southward flow) varies
between a minimum transport of 7 Sv in winter (July) to a maximum of 16 Sv in
summer. The semiannual frequency components of h and P
is important near 30°S near the EAC outflow, but not elsewhere. The
seasonal cycle of the EAC is not due to strong seasonal
variations in Tasman Sea wind stress curl east of the region of interest.
Seasonally reversing zonal flows occur offshore north
of 25°S, which are apparently locally forced by
reversing wind stress curls; but if
these flows were fed from the south by the EAC current
system, the EAC would have to be weaker in summer, not stronger. The
Leeuwin Current Extension along Australia's west and south
coasts may pass up the east coast of Australia, providing an important
contribution to the enhanced southward flow of the EAC in
summer. The vigorous anticyclonic eddies of the EAC also show a marked
seasonal cycle and this is probably an important part of the
mechanism for the strong seasonal cycle of the EAC south of 25°S. The
location of the strongest anticyclonic eddy in the EAC moves
steadily southward throughout the summer season, and the phase of the
coastal EAC appears also to move southward contrary to the
expectations of linear theory, and to the hypothesis that the Leeuwin
Current Extension is the major cause of the seasonal cycle.
See Ridgway and Godfrey (1997) and
Tomczak and Godfrey (1994).
- East Cape Current
- See East Auckland Current.
- East China Sea
- See Tomczak and Godfrey (1994),
Jilan (1998) and
Katoh et al. (2000).
- East Coast Ocean Forecast System (ECOFS)
- A cooperative program among NOS,
NCEP, GFDL, and
AOS to develop a system capable of
producing useful nowcast and
forecast information for the east coastal region of the
ECOFS Web site.
- East Greenland Current
- More later.
See Foldvik et al. (1988) and
Woodgate et al. (1999).
- East Greenland Ice Stream
- See Wadhams (1986).
- East Greenland Polar Front
- See Johannessen (1986).
- East Icelandic Current
- See Swift (1986).
- East Icelandic Water
- A water mass found in the area of
the Iceland-Faroe Ridge.
See Hansen and Osterhus (2000).
- East India Coastal Current
- See Shankar et al. (1996).
- East Indian Current
- A seasonal and northward flowing current found in the western part of
the Bay of Bengal from about January
until October. The weak and variable currents found early in the
year strengthen with the Northeast Monsoon, exceeding 0.5 m/s
by March and ranging from 0.7-1.0 m/s through May and June.
This current flows counter to the wind, apparently as an
extension of the
North Equatorial Current,
although a convincing dynamical explanation has yet to be offered.
The northward flow gradually weakens with the advent of the
Southwest Monsoon, with the currents to the north and close
to the shelf beginning to reverse in September. By late October,
the East Indian Current has completely reversed into the
East Indian Winter Jet.
See Tomczak and Godfrey (1994).
- East Indian Winter Jet
- A seasonal southwestward flowing
western boundary current
found in the western Bay of Bengal
from late October through around late December. It features
velocities consistently above 1 m/s as it flows southwestward,
eventually turning west and following topographic contours as it
passes Sri Lanka and feeds all its waters into
the Arabian Sea. In late December
its northern part fades, eventually to become the
East Indian Current, and
the southern part merges with the developing
North Equatorial Current.
- East Korea Current
- See Tsushima Current.
- East Sea
- A semi-enclosed, marginal sea surrounded by Korea, Japan and Russia.
See Preller and Hogan (1998).
- East Siberian Sea
- One of the seas found on the Siberian shelf in the
Arctic Mediterranean Sea.
The western boundary passes from the meridian at the northern tip
of Kotelny Island along the continental shoal margin
(79 N, 139 E) to the northern end (Anisiy Cape),
then along the western shore floolwing the eastern boundary of
the Laptev Sea. The northern boundary
passes by the edge of the continental shoal from 76 N,
180 E, then along the eastern boundary along meridion
180 up to Wrangel Island, then along the northwestern
shore to Blossom Cape, and then down to Yaken Cape on the mainland.
The southern boundary passes along the mainland coast from Yakan Cape
to Svyatoy Nos Cape.
the Laptev Sea
to the west, the Chuckchi Sea
to the east and the
Arctic Ocean proper to the
The largest span is about 640 nautical miles, and the largest
width about 506 nautical miles.
The bathymetry is very level and comparatively shallow compared with
the other marginal seas of the Arctic Basin. The prevailing depths
of the western and central regions are 10-20 m, and 30-40 m in the
The first scientific data from this sea was collected on the 1922-1924
expedition of the Maud and published by
Sverdrup (1929). This remained the only accessible data
until the military vessels USS Barton and USCGS Northwind
surveyed the area in 1962 and 1966.
The first U.S. research vessel to enter the East Siberian Sea was the
RV Alpha Helix in 1995. It deployed surface drifters in the
ice-free summer shelf waters and conducted hydrographic surveys to
investigate the influence of the Kolyma River on the shelf circulation.
The freshwater input of the Kolyma River is of prime hydrographic
significance to the East Siberian Shelf Sea. The annual discharges
vary from below 2000
to nearly 5000
with the 1936-1996 mean about 3160
. The discharge is
highly seasonal with more than 90% occurring between June
and September, increasing from a May average of less than
to a June average of more than
(with the average monthly discharge during the
winter from November through April less than
The Lena River to the west also contributes fresh water, with a peak
discharge that can exceed 100,000
The waters of the East Siberian Sea are fresh and cold, with surface
temperatures varying between 0 and 2C and bottom
temperatures near the freezing point. Large horizontal salinity
(although not temperature) gradients are found at depth.
The shelf waters are generally colder, saltier, and thus denser than
the offshore waters. The salinities range from almost 0 near the
Kolyma River mouth to a maximum of 33. The three most significant
water masses are resident shelf waters, freshwater from river discharges,
and freshwater from seasonal ice melt.
The buoyancy forcing due to the freshwater input would be expected
to result in an eastward bound buoyancy-driven flow coastal current,
but the drifters in a 1995 survey (Münchow et al. (1999))
indicated a 50-day mean westward flow reaching 0.1 .
The river waters were found to be predominant only in the immediate
vicinity of the Kolyma Delta.
The observed circulation was postulated to be due to some as yet unknown
See Sverdrup (1929),
Münchow et al. (1999) and
Münchow et al. (1999).
- a line source of buoyancy caused by the melt water left by an
ice edge that retreated 100 km in less than two weeks;
- large-scale barotropic and/or baroclinic pressure gradients imposed
from the Laptev Sea in the west through Laptev Strait; and
- decadal-scale scale climate oscillations (i.e. atmospheric pressure
anomalies) that induce alternating
cyclonic and anticyclonic circulation regimes.
- East Spitsbergen Current
- See Pfirman et al. (1994).
- East Wind Drift
- The westward flowing current close to the Antarctic continent
driven by the polar easterlies.
- Eastern Atlantic Experiment (EAE)
- A 1996-1997 experiment that was one of the three main components
forming the MAGE component of
EAE was an extensive study of the speciation of sulphur and nitrogen in
both clean and moderately polluted atmospheres, and involved the
measurement of DMS and other gases in the ocean and
the calculation of fluxes into the atmosphere, combined with the
measurement of the speciation of sulphur and nitrogen in both gas and
size-fractionated aerosol phases.
The objectives were:
- to quantify the input of DMS into a parcel of air;
- to examine the oxidation of DMS and its reaction with nitrogen
species with time;
- to investigate the formation of new particles that result from these
- to discriminate between natural and anthropogenic fractions of sulphur
and nitrogen using isotopic measurements.
- eastern boundary current
- See Wooster and Reid (1963).
- Eastern Equatorial Pacific (EEP)
- See Wyrtki (1966).
- Eastern Mediterranean Deep Water (EMDW)
- A water mass found in the
EMDW extends from the overlying
Levantine Intermediate Water (LIW)
to the bottom, although the
layer of EMDW between 700 m and 1600 m is considered
transitional since it is modified by LIW.
This layer has been called
Transitional Mediterranean Water (TMW).
The Adriatic Sea is considered the
source of cold and less saline EMDW, which is formed in the winter
in the Ionian Sea by the mixing of deep and cold
Adriatic water (that enters the
Otranto Strait) with transformed LIW and, to a lesser extent, by
mixing with deep Cretan waters.
The core values of the EMDW are remarkably invariant through the basin
with 13.4 C, T = 13.6 C, S = 38.7, and
29.17 kg m.
See POEM Group (1992), Roether et al. (1996),
Malanotte-Rizzoli et al. (1997),
Stergiou et al. (1997) and
Theocharis et al. (1999).
- Eastern North Atlantic Water (ENAW)
- A water mass defined by Harvey (1982) and
() to describe water found west of
Ireland and Iberia.
The ENAW definition can be subsumed into the broader definition of
North Atlantic Subpolar Mode Water,
and thus can be seen as a variety of the latter.
See Read (2001).
- Eastern North Atlantic Central Water (ENACW)
- See Poole and Tomczak (1999).
- Eastern North Pacific Central Water (ENPCW)
- In physical oceanography, a water mass
formed in the region of the surface salinity maximum just south of
30 N where salinities greater than 35 are found year round.
This is reflected in the portion of ENPCW above 17 C, which
has salinities higher than those of all other water masses in the
vicinity. It is fresher than both WNPCW
and NPEW at temperatures below 17 C,
and saltier in the upper thermocline waters warmer than this.
It is bounded to the west from WNPCW
at about 170 E, and to the south from NPEW
at about 12-14 N.
See Tomczak and Godfrey (1994), p. 165.
- Eastern South Atlantic Central Water (ESACW)
- See Poole and Tomczak (1999).
- Eastern South Pacific Central Water
- In physical oceanography, a water mass
formed between 150-180 W (by processes not yet well understood)
and separated from the
WSPCW by a gradual transition zone
from 145-100 W., from which it is distinguished as being
fresher at all T-S values. It is bound to the north by
SPEW, from which it is also distinguished
by being fresher at all T-S points, to the south by the
STC, and to the east by a not yet well understood
area having salinities as low as 34.1 east of 90 W.
See Tomczak and Godfrey (1994), p. 164.
- Acronym for Eastern Tropical Pacific, a research project.
- Abbreviation for
East Arabian Sea Water.
- Acronym for European Atlantic Time and Space Series study, a proposed
program for establishing coordination of European research activities
along the historically studied 20W meridian from
20 to 60N.
EATTS will be sponsored under the auspices of
- Abbreviation for Energetically Active Zones of the Ocean.
- ebb current
- The tidal current existing during any time the height of the
tide is decreasing. These generally flow in a seaward
direction. This has been erroneously called ebb tide.
- ebb interval
- The interval between the transit of the moon over a meridian
and the time of strength of ebb of the following tide.
- ebb strength
- See strength of ebb.
- ebb tide
- See falling tide.
- Abbreviation for
eastern boundary current.
- Acronym for Estimating the Circulation and Climate of the Ocean,
a consortium consisting of MIT, JPL and SIO formed under the
NOPP and funded by NSF, NASA and ONR.
The consortium intends to bring ocean state estimation from
its current experimental status to that of a practical and quasi-operational
tool for studying large-scale ocean dynamics, designing
observational strategies, and examining the ocean's role in climate variability.
The central goal is the production and evaluatino of continuing 3-D
estimates of the global state of the ocean, and the main task is to
bring together a global GCM with existing global data streams to obtain
the best possible estimate of the time-evolving ocean circulation and
- A recording echo sounder.
- echo sounder
- An instrument used to determine ocean depth by measuring the time needed
for a sound wave to travel from the ship to the ocean floor and return.
The first reliable acoustical sounding machine was built by A. Behm
in 1919, who called it an echo sounder.
An echo sounder consists of three main components: the sound transmitter,
the sound receiver, and a device to measure time.
See Dietrich (1963).
- Eckart, Carl (1902-1973)
- See Munk and Preisendorfer (1988).
- Acronym for Etudes Climatiques dans l'Atlantique Tropical, a
multidisciplinary program designed to become the French
contribution of CLIVAR in
the tropical Atlantic. The PIRATA
program will be part of ECLAT.
ECLAT Web site.
- A research cruise carried out on the R/V Hesperides from Jan. 2
to Feb. 1, 1994 in the eastern basin of the
A total of 130 hydrographic stations were occupied, and 180 surface to
bottom profiles collected.
See López et al. (1999).
- A program to study shelf edge exchange processes in the
Gulf of Lions.
See Monaco et al. (1990).
- eddy correlation technique
- A method for estimating the ocean surface
wind stress wherein the directional components
of the near-surface turbulent stress covariance in the atmospheric
boundary layer are measured.
The vertical stress is defined as:
is the horizontal vector velocity and
the vertical velocity component.
In terms of its scalar components, the magnitude of the wind stress
is given by:
and its angle to the mean wind is:
where and are the horizontal velocity components.
The overbar represents the mean value over a suitable averaging interval.
The data must be measured over sufficiently large time and space scales
to capture all scales of variability, a task that inevitably presents
- eddy conduction
- See eddy heat flux.
- eddy conduction coefficient
- See eddy conductivity.
- eddy conductivity
- The exchange coefficient for the transfer of heat by eddies
in turbulent flow, i.e. eddy heat flux. This is also
called the eddy conduction coefficient.
- eddy diffusivity
- eddy heat conduction
- See eddy heat flux.
- eddy heat flux
- In physical oceanography, the total meridional heat transport due
to mesoscale eddies. This has also been used to refer to the
correlation of time-dependent fluctuations of velocity and
temperature across a section, which is not indicative of the
total heat transport due to eddies. Eddies can also induce
a thermally driven, overturning cell in subtropical gyres that
is analogous to the Ferrel cell
in the atmosphere. This cell contributes to the time-averaged
transport and its contribution may be as large as that of the
This is also called eddy conduction or eddy heat conduction.
See Cox (1985).
- eddy-induced transport velocity
- An additional velocity which must be added to the large-scale
velocity to properly advect large-scale tracers in numerical
circulation models. This is due to the effective transport
velocity not being equivalent to the Langrangian-mean
velocity when the diffusivity is not spatially homogeneous.
This is defined in isopycnal coordinates as:
is the horizontal velocity,
the isopycnal thickness, and the tilde
represents an average along an isopycnal surface.
This quantity is important since average tracer quantitues are advected
by not just the Eulerian mean velocity
the total transport velocity given by:
This velocity is a turbulence correlation and therefore must be specified
by some type of turbulence theory or parameterized. One attempt at the
latter defines it as:
is the horizontal gradient in isopycnal
coordinates and is a scalar diffusivity coefficient.
This is also known as the
See Gent et al. (1995) and
Dukowicz and Greatbatch (1999).
- eddy viscosity
- A coefficient used to achieve
closure in the
Reynolds equations for
turbulent flow. The assumption is made that the
Reynolds stresses are related
to the velocity gradients of the flow by a viscosity analogous
to the molecular viscosity, i.e. a turbulent
or eddy viscosity.
The utility of the analogy is strained by the fact that while
the molecular viscosity is a property of the fluid, the eddy
viscosity is a property of the flow. As such the specification
of the eddy viscosity has more than a little of the air of the ad hoc
about it since it is usually found via a trial-and-error procedure
wherein it is varied until a numerically simulated flow reasonably
replicates a known flow. The value thus obtained diagnostically
is then used for prognostic simulations, a procedure that is
questionable due to the abovementioned fact of the eddy viscosity
being a property of the flow rather than the fluid. That is, if the flow
is remarkably different, then the eddy viscosity may also be
In the ocean eddy viscosity values range typically from
10 to 10**5 m2/s in the horizontal and from 10**-5 to 10**-1 m2/s in
the vertical, with both values more often found towards the higher
ends of their ranges.
- edge wave
- A wave which travels parallel to a coastline with crests normal
to the coastline. The height of the wave diminishes rapidly
- Abbreviation for Eddy Damped Quasi-Normal Markovian, a subfilter
closure model applied in spectral wavenumber space rather than
physical space which considers interactions between resolved
and subfilter wavenumbers by considering the statistics
of their possible interactions.
The EDQNM achieves closure by modeling the 4th spectral
moments. The is one of several closure techniques used when applying
large eddy simulation model.
See Mason (1994).
- Abbreviation for eastern equatorial Pacific.
- effective scattering cross-section
- The ratio of backward scattering intensity to density of
See Kagan (1995).
- effective transport velocity
- The sum of the large-scale velocity and the
eddy-induced transport velocity. This is velocity at which
tracers are advected in large-scale circulation models.
See Gent et al. (1995).
- e-folding time
- The time it takes a system to reduce an imposed displacement to
a factor of 1/e of the displaced value. This is a common way
of expressing the
equilibration time of a system.
The e-folding concept is often applied
to distances as well as times.
- Abbreviation for Eddy-resolving General Circulation Model.
- Acronym for the European Emiliania huxleyi program,
a comprehensive experimental and modeling program focused on
the calcium carbonate and organic carbon productivity
and ocean carbon flux induced by E. huxleyi in the
Northeast Atlantic region. It is a component of and
complementary to the GEM program.
This project aims to characterize the nonlinear nature of
the biological involvement in ocean chemistry and the
coupling of the fluxes of particulate organic carbon (POC)
and particulate inorganic carbon (PIC).
The fundamental objective is the improve understanding of
the processes involved in the growth, distribution and
role of E. huxleyi in the oceanic carbon cycle.
The specific aims include the morphological and genetic
characterization of clones from different areas and elucidation
of the life cycle; characterization of PIC, POC, biomarker
and CO productivity as a function of cellular and molecular
organization and life cycle stages; parallel mesocosm experiments;
quantification of these processes in natural blooms at different
stages of development and development of carbon budgets for
well defined spring bloom conditions; and the development
of descriptive and predictive models.
See the EHUX Web site
and Harris (1996).
- Abbreviation for
Equatorial Intermediate Current.
- 18 Water
- A variety of
Subtropical Mode Water (STMW)
that forms in the western
subtropical gyre of the
North Atlantic Ocean, i.e. the area known as the
This has also been called Sargasso Sea Water (SSW).
See Worthington (1959) and Talley and McCartney (1982b).
- Abbreviation for
entrainment interfacial layer.
- Abbreviation for Echo Integration-Midwater Trawl.
- Abbreviation for eddy kinetic energy.
- Ekman current meter
- A mechanical current meter that comprises a propeller with
a mechanism to record the number of revolutions, a compass
and a recorder with which to record the direction, and a vane
that orients the instrument so the propellor faces the current.
It is mounted on a free-swinging vertical axis suspended from
a wire and has a weight attached below. The balanced propellor,
with from four to eight blades, rotates inside a protective
ring. The position of a lever controls the propeller. In
down position the propellor is stopped and the instrument is
lowered, after which reaching the desired depth a weight called
a messenger is dropped to move the lever into the middle position
which allows the propeller to turn freely. When the measurement
has been taken another weight is dropped to push the level to
its highest position at which the propeller is again stopped.
The propeller revolutions are counted via a simple
mechanism that gears down the revolutions and counts them
on an indicator dial. The direction is indicated by a
device connected to the directional vane that drops a small
metal ball about every 100 revolutions. The ball falls into
one of thirty-six compartments in the bottom of the compass
box that indicate direction in increments of 10. If the
direction changes while the measurement is being performed
the balls will drop into separate compartments and a weighted
mean is taken to determine the average current direction.
This is a simple and reliable instrument whose main disadvantage
is that is must be hauled up to be read and reset after each
measurement. Ekman solved this problem by designed a repeating
current meter which could take up to forty-seven measurements
before needing to be hauled up and reset. This device used
a more complicated system of dropping small numbered metal balls at
regular intervals to record the separate measurements.
See Sverdrup et al. (1942).
- Ekman repeating current meter
- See Ekman current meter.
- Ekman dynamics
- In oceanography, the process of surface wind stress driving a
relatively shallow upper ocean flow that transports water to the
left/right and the southern/northern hemisphere.
- Ekman layer
- To be completed.
See Price and Sundermeyer (1999).
- Ekman number
- In oceanography, a
expressing the ratio of
frictional (or viscous) to Coriolis forces.
It can be expressed as
where is the kinematic viscosity, a vertical length scale,
and the Coriolis parameter.
A small Ekman number can be interpreted as the condition that frictional
forces are sufficiently weak such that the natural decay time due to
viscous dissipation in the Ekman layer is large compared to a rotation
period, i.e. that the spin-down is dominated by rotational rather
than frictional processes.
See Kraus and Businger (1994) (p. 31) and
Pedlosky (1982) (p. 180).
- Ekman pumping
- In oceanography, a process that is the result of a combination
of Ekman dynamics and horizontal variations
in the wind stress. The resulting convergence and divergence of
the surface flow will force vertical water motion called
Ekman pumping or suction, respectively.
- Eliassen-Palm flux
- A concept originally developed as a diagnostic tool for studying the
interaction between eddies and the zonal-mean flow in the atmosphere.
The Eliassen-Palm flux vector is used to represent eddy momentum and
heat transport in such a way that the total eddy-inducing forcing
is the divergence of the Eliassen-Palm flux.
It can also be used to provide information about wave activity for
quasigeostrophic flows, with this application relying on the equality
between the divergence of the flux and the eddy potential vorticity
flux under the quasigeostrophic approximation.
See Lee and Leach (1996).
- Acronym for Eddies and Leddies Interdisciplinary Study off Algeria,
a MAST-3/MATER program and companion to the
ELISA was an interdisciplinary project to investigate the
Western Mediterranean Sea, looking at the role of the Algerian
Basin through the detailed study of the Algerian Current.
The field work took place between July 1997 and July 1998 and
involved 44 scientists from 8 countries.
The objectives were to study:
- the general circulation of the water masses, i.e.
MAW, LIW and
- the Algerian eddies origin, structure and trajectories;
- the biological activity associated with the mesoscale dynamic
- the role of the mesoscale dynamics on the biological functioning
of the Algerian Basin.
- El Niño
- A term originally applied as a description of an annual weak warm current
running southward along the coast of Peru and Ecuador during the
Christmas holiday, i.e. the Spanish word for ``the boy Christ-child''
The name El Nño
eventually became associated with unusually large warmings
that occur every few years and effect large changes on the local,
regional, and even global climate.
It gradually became known that the coastal warming was part of a
much larger warming of the upper waters of the Pacific extending as
far as the international date line.
There is an associated atmospheric phenomenon called the Southern
Oscillation, with the combined changes in atmosphere
and ocean termed
El Niño/Southern Oscillation or ENSO, with El Niño properly
referring the warm phase of ENSO. A typical El Niño event begins
in the nothern spring or sometimes summer, peaks from November
to January in SSTs, and ends the following summer.
The opposite phase is similarly called La Niña, i.e.
Spanish for ``the girl,'' and features a basinwide cooling in the
The entire system is called El Niño in many if not most popular
More quantitative definitions have been proposed for classification
purposes. Although none is recognized as official, several objective
methods have proved useful. Most involve calculating the
deviation from average of temperatures in
rectangular regions in the tropical Pacific, with the averaging
period, baseline temperatures, qualifying deviation, and specific region
varying from definition to definition.
The defined averaging regions include:
Niño 3 (5N-5S, 90-150W);
Niño 3.4 (5N-5S, 120-170W); and
Niño 3.5 (5N-10S, 120-180W).
A typical calculation would find periods during which 5 month
running means of monthly SST anomalies in a given area are +0.4C
or more for at least six consecutive months.
According to Trenberth (1997), applying this particular procedure to
Niño 3.4 picks out most historically
prominent El Niño events.
Neelin et al. (1994),
Neelin et al. (1998),
Philander and Rasmusson (1985) and
Stockdale et al. (1998).
- El Niño/Southern Oscillation
- See El Niño.
- See Kuhl (1972).
- electromagnetic fields
- See Tyler et al. (1997).
- Abbreviation for
Eastern Mediterranean Deep Water.
- 1. Acronym for Equatorial Mesoscale EXperiment, an experiment
conducted over the tropical oceanic area north of Australia
in Jan.-Feb. 1987. It explored the vertical air motions
and other kinematic properties of tropical mesocale
convective-cloud systems by direct aircraft penetration.
The objectives of EMEX were to document, as intensively
and directly as possible, the vertical profile of vertical
velocity and other kinematic structures over the ocean near
the equator with the most up-to-date instrumentation
available and to investigate the physical mechanisms responsible
for the convective and stratiform components of the
observed cloud systems.
See Webster and Houze Jr. (1991).
2. Acronym for Equatorial Monsoon Experiment.
- The ratio of the emittance from a body to that of a black body
emitter at the same temperature, i.e. the degree to which a real
body approaches a black body radiator.
- The rate at which radiation is emitted from a unit area.
- empirical normal mode (ENM)
- Basis functions that have both the statistical properties of
empirical orthogonal functions (EOFs)
and the dynamical properties of
normal modes, although the orthogonal
products used to define orthogonality are related to conserved
wave activities such as
These are obtained in a manner similar to EOFs by the diagonalization
of a general hermitian problem but with the
use of a quadratic form instead of the Euclidean norm, with
the quadratic form being a global invariant of the linearized
equations about a basic state.
ENMs are a diagnostic tool for studying wave behavior and wave
interactions, and can also be used as predictors in a long-range
They typically beat EOF-based forecasts at long lead times but
have slightly poorer scores at short lead times since ENMs are
less efficient for data compression than EOFs.
See Brunet and Vautard (1996).
- empirical orthogonal function (EOF)
- EOF analysis provides a convenient method for studying the spatial
and temporal variability of long time series of data over large
areas. It splits the temporal variance of the data into orthogonal
spatial patterns called empirical eigenvectors. A set of orthogonal
spatial modes can be identified such that, when ordered, each
successive eigenvector explains the maximum amount possible of the
remaining variance in the data, and each eigenvector pattern is
associated with a series of time coefficients that describe the
time evolution of the particular spatial mode.
The modes are orthogonal, which means that any two modes are
uncorrelated in space and time and, as such, no one mode is related
to any other. See Peixoto and Oort (1992)
and Preisendorfer (1988).
- See Eurafrican Mediterranean Water.