Abbreviation for Antarctic Bottom Water.
Abbreviation for Antarctic Circumpolar Water.
Abbreviation for annual actual
a variable used in the
Thornthwaite scheme for
bioclimate classification. The AAE depends on the monthly
values for potential evapotranspiration, precipitation and
soil moisture storage as detailed in Thornthwaite (1948).
Antarctic Intermediate Water.
Abbreviation for Airborne Antarctic Ozone Experiment,
a program taking place in late Winter 1987
to acquire the scientific observations needed to
understand the Antarctic ozone hole.
AAOE Web site.
Abbreviation for Atomic Absorption Spectroscopy.
Abbreviation for Airborne Arctic Stratospheric Expedition,
a NASA experiment to study the production and loss mechanisms
of ozone in the north polar stratospheric environment and to
study the effect on ozone distribution of the Arctic polar
vortex and of the cold temperatures associated with the
formation of polar stratospheric clouds (PSCs).
AASE Web site.
Abbreviation for the American Association of Stratigraphic
Palynologists, founded in 1967 to promote the science of
palynology. See the
AASP Web site.
Antarctic Surface Water.
Abbreviation for Arctic Acoustic Transmission Experiment,
a project of the APL at the University
of Washington School of Oceanography.
Abbreviation for Advanced Along-Track Scanning Radiometer.
atmospheric boundary layer.
The removal of mass from a glacier by the processes of
surface melting, evaporation, and iceberg calving.
- ablation zone
One of five glacier zones used
to categorize areas on glaciers in terms of ice temperature
and melting. The ablation zone is the area below the
equilibrium line below
which there is a net loss of ice over the year. The
superimposed ice zone
exists above this line.
Acronym for Arctic Boundary Layer Expeditions (or Experiment).
Abbreviation for Acoustic Backscatter Probes.
Acronym for Anglo-Brazilian Amazonian Climate Observation Study,
the objectives of which were to monitor Amazonian climate,
improve the understanding of the consequences of deforestation,
and to provide data for the calibration and validation of GCMs
and GCM sub-models of Amazonian forest and post-deforestation
See Roberts and Cabral (1993) and the
ABRACOS Web site.
Violent squalls on the coast of Brazil that
prevail from May to August.
- absolute humidity
The ratio of the mass of water vapor in a sample of moist air to
a unit volume of the sample. It is expressed in grams per
cubic meter and also called the vapor
- absolute vorticity
The sum of the
relative vorticity ( )
planetary vorticity, i.e.
In radiation transfer, the fraction of incoming radiation that
is absorbed by a medium.
The sum of this, the transmittance,
and the reflectance must equal unity.
A process by which incident radiation is taken into a body and
retained without reflection or transmission. It increases either the
internal or the kinetic energy of the molecules or atoms composing
the absorbing medium.
- absorption band
In atmospheric radiative transfer,
a collection of absorption lines
in a particular frequency interval.
- absorption line
In atmospheric radiative transfer,
a discrete frequency at which an energy transition of an atmospheric
gas occurs due to the absorption of incident solar radiation.
The line width depends on broadening processes, the most important
of which are natural,
pressure (also known as collision), and
In bioclimatology, an
abbreviation for annual biotemperature, a variable used in the
Holdridge system. It is
defined as the annual mean of monthly mean temperatures, where
the monthly means are those above .
See Arctic Bottom Water.
- abyssal hill
Small hills found only in the deep sea which rise from the
ocean basin floor with heights ranging from 10 to over 500 feet
and widths from a few hundred feet to a few miles.
They are found along the seaward margin of most
abyssal plains and originate
from the spreading of mid-ocean ridges. As such, they usually
form two strips parallel to mid-ocean ridges. They generally
decrease in height as one traverses away from the ridges as
they gradually become covered with sediment and are replaced
by abyssal plains.
See Fairbridge (1966).
- abyssal plain
Flat areas of the ocean basin floor which slope less
than 1 part in 1000. These were formed by
which covered the preexisting topography.
Most abyssal plains are located between the base
of the continental rise
and the abyssal hills.
The remainder are trench abyssal plains that lie in the
bottom of deep-sea trenches. This latter type traps all
sediment from turbidity currents and prevents abyssal
plains from forming further seaward, e.g. much of the
Pacific Ocean floor.
See Fairbridge (1966).
- abyssal zone
This originally meant (before the mid-1800s) the entire depth
area beyond the reach of fisherman, but later investigations led
to its use being restricted to the deepest regions with a uniform
fauna and low temperatures. Thus it was distinguished from
the overlying bathyal or archibenthal zone with more varied
fauna and higher temperatures. Eventually an underlying
hadal zone was defined for areas
in trenches and deeps below 6000-7000 m depth.
The upper boundary of the abyssal zone
ranges between 1000-3000 m, with the position of the
4 C isotherm generally considered the demarcation line.
It is the world's largest ecological unit, with depths exceeding
2000 m comprising over three-quarters of the world ocean.
See Fairbridge (1966).
- abyssopelagic zone
One of five vertical ecological zones into which the
deep sea is sometimes divided.
There is a pronounced drop in the number of species
and the quantity of animals as one passes into this zone.
It is separated from the overlying
by the 4 C isotherm and from the underlying
at about 6000 meters. The distinction between
benthic species can be
difficult to ascertain in this zone.
See Bruun (1957).
Acronym for Airborne Chromatograph for Atmospheric Trace Species,
an instrument used for the measurement of several species important
in the chemistry related to stratospheric ozone depletion such
as N O, sulfur hexafluoride (SF ), and a wide range of
chlorinated hydrocarbons including the CFCs. This was built
as a collaborative effort between the NOAA
Aeronomy Laboratory (AL) and
Climate Monitoring and Diagnostics Laboratory (CMDL) programs.
ACATS is both an ongoing project and a series of instruments
for that project.
ACATS Web site.
1. Abbreviation for the
Antarctic Circumpolar Current.
2. Abbreviation for the
Alaskan Coastal Current.
Abbreviation for Atlantic Climate Change Experiment, an experiment
planned to study the role of the Atlantic thermohaline circulation
in global atmospheric climate. It will take place largely in the
North Atlantic region, including the equatorial basin where drifters
will be employed.
ACCE Web site.
1. In physics, this means one thing.
2. In heterochrony, this is a type of
peramorphosis that occurs as an increase
in the degree of allometry. For
meristic characters it is an increase in the rate
of production of structures.
Acronym for the Antarctic Circumpolar Current Levels by Altimetry and
Island Measurements program in the South Atlantic and Southern
Oceans. It consists of measurements from coastal tide gauges and
bottom pressure stations, along with an ongoing research program
in satellite altimetry. See the
ACCLAIM Web site.
Abbreviation for the Atlantic Climate Change Program, a
initiative for understanding the decadal-scale interactions of
deep circulation in the Atlantic and how it influences the
overlying atmosphere. See the
ACCP Web site.
- accumulation mode
One of three categories used to summarize the
distribution of atmospheric aerosols in terms of production
mechanism and particle size, the others
being the nucleation and
coarse particle modes.
The accumulation mode ranges in size from 0.1 to 1 m in
diameter and its production mechanism is by coagulation and
See Jaenicke (1993b).
The degree of freedom from error. The total error compared to a
theoretically true value. Contrast with and see
for an example.
1. Abbreviation for Antarctic Current Experiment, a
2. Abbreviation for Aerosol Characterization Experiments, a part of
the IGAC program. ACE-1 is the first of
a series of experiments that will quantify the chemical and
physical processes controlling the evolution and properties
of the atmospheric aerosols relevant to radiative forcing and
climate. The ultimate objective of these studies is to
provide the data necessary to incorporate aerosols into
global climate models and reduce the overall uncertainty in
the calculation of climate forcing due to aerosols.
ACE-1 will document the chemical, physical and radiative
properties and determine the controlling processes of the aerosols
in the remote marine atmosphere, while ACE-2 will extend these
characterization and process studies to the North Atlantic with
an emphasis on the anthropogenic perturbations of the background
ACE Web site.
3. Abbreviation for Advanced Composition Explorer, a
- acid rain
The deposition on land and water
of strong acids (H SO , HNO ) in the form of rain, snow, fog,
cloud water, and dry deposition. These acids are formed by the
oxidation of SO and NO emitted to the atmosphere during the
combustion of fossil fuels.
See Bricker and Rice (1993).
Abbreviation for Advisory Committee on the Marine Environment, an
- acme biozone
a type of biozone that relies for definition on the
recognition of a maximum occurrence of a fossil that might otherwise
range both higher and lower in the succession.
See Briggs and Crowther (1990), pp. 466-467.
Abbreviation for Advisory Committee on Marine Pollution, an
Abbreviation for Advisory Committee of Experts on Marine Resources
Research, a FAO committee.
Abbreviation for the Atmospheric Chemistry Modeling Support Unit,
a part of UGAMP located at the Center for
Atmospheric Science at Cambridge, U.K. The ACMSU is responsible
for provision of the chemical data and codes to the rest of
UGAMP. See the
UGAMP Web site.
Abbreviation for Advisory Committee for Operational Hydrology, a
Abbreviation for Advisory Committee on Oceanic Meteorological
Research, an WMO committee.
Abbreviation for Advisory Committee on Protection of the Sea.
- acoustic signature
A set of characteristics used to describe a sound signal.
This may include sound echos from targets, radiated and
ambient noise, with salient echo characteristics including
target strength, spectral reflectivity versus frequency,
doppler shift, doppler spread and target range extent.
- acoustic tomography
The inference of the state of the ocean from precise measurements
of the properties of sound waves passing through it.
This technique takes advantage of the facts that the properties
of sound in the ocean are functions of temperature, water velocity
and other salient oceanographic properties and that the ocean
is nearly transparent to low-frequency sound waves. These felicitous
circumstances combine to allow signals transmitted over hundreds to
thousands of kilometers to be processed with
inverse methods to obtain
estimates of large-scale fields of ocean properties.
An especially advantageous feature of this method is that, given
the 3000 knot speed of sound in the ocean, reasonably
synoptic fields can be constructed.
The chief problems presently encountered in this field are
those related to engineering sufficiently accurate transmitters
and receivers for the task.
See Munk et al. (1995).
- acoustical oceanography
The study of sound propagation in the ocean and its underlying
sediments. This ranges from the earliest use of
to chart the ocean floor to the use of
SONAR to locate
schools of fish, underwater vehicles and ocean drifters to
the most recent applications of
acoustic tomography to infer
large-scale properties of the ocean and the ocean floor.
Acronym for Active Cavity Radiometer Irradiance Monitor, an experiment
that provides long-term, precise
measurements of the total amount of the Sun's energy that falls on
the Earth's surface, oceans and atmosphere.
ACRIM-I flew on the
SMM from 1980-1989 and ACRIM II is currently
operating on NASA's UARS mission. See the
ACRIM Web site.
An organic-walled and spheroidal microfossil of uncertain
taxonomic status. Some consider them to be the cysts of
eukaryotic algae. See Bowen (1991).
Acronym for the Applied Climate Research Unit at the University
of Queensland, which performs research into such areas as
biometeorology, rainfall prediction, and rural production. See the
ACRU Web site.
Abbreviation for the Arctic Climate System Study, a
WCRP program whose goal to to ascertain
the role of the Arctic in global climate. The primary scientific
goals are to provide an adequate basis for representation of the
Arctic in coupled global models, to develop plans for effectively
monitoring the climate in the Arctic, and the determine the role
of the Arctic in the sensitivity and variability of global
ACSYS Web site.
- actinic flux
Name given to spherical spectral
radiant flux density in the
atmospheric photochemistry community. It is the photochemically
effective flux and the units are photons/cm**2/s/nm over a series
of narrow wavelength intervals. No instruments are available to
measure this, and it is usually approximated using
chemical actinometry techniques.
See Jeffries (1995).
- actual evaporation
The actual amount of water vapor released from a land or water surface,
as opposed to potential evaporation.
Abbreviation for Acoustic Doppler Current Profiler, an instrument used
to measure ocean currents. It transmits high frequency acoustic
signals which are backscattered from plankton, suspended sediment,
and bubbles, all of which are assumed to be traveling with the
mean speed of the water. The Doppler shift in the backscatter
echo allows the water velocity to be determined. Further processing
of the received signals allows a profile of current speed and direction
to be determined.
The ADCP measures the ocean current velocity continuously over the
upper 300 m of the water column, usually in 8 m depth increments.
It is also used to estimate the abundance and distribution of
biological scatterers over the same depth range and in the
same depth increments.
ADCP data collection requires that four instruments work together.
These are the ADCP itself, the ship's gyrocompass, a
GPS receiver, and a GPS Attitude
Determination Unit (ADU). See
NODC's Shipboard ADCP Center (SAC).
Acronym for the Advanced Earth Observing Satellite to be launched
by Japan in February 1996. It will be launched into a solar-synchronous
sub-recurrent orbit in a recurrent period of 41 days at an altitude
of about 800 km. The goal is to collect data appropriate for
monitoring environmental changes such as global warming, ozone
layer depletion, decrease in tropical rain forests, unusual
weather occurences, etc. The instruments ADEOS will carry
include AVNIR, ILAS,
RIS, and TOMS.
- Adhemar, Joseph Alphonse
A French mathematician who was the first to suggest that the
prime causal mechanism of the ice ages might be variations in the way the
earth moves around the sun. He published this suggestion in a book
entitled Revolutions of the Sea in 1842.
He reasoned that the
precession of the equinoxes, presently causing the southern
hemisphere to have more hours of darkness per year than daylight,
was what caused and maintained the ice sheet on Antarctica.
He then theorized that the cycle of the precession of the equinoxes
would cause whatever hemisphere was having the longer winter to
have an ice age.
It is now well known that the centering of the large Antarctic
land mass over the South Pole shields any ice or snow that forms
there from the moderating effects of the ocean and, combined with
the process of ice-albedo feedback,
keeps the continent cold enough to form an ice sheet. It is also now
known that the total amount of heat received by a hemisphere during
the year is the same for both. Although Adhemar was wrong about
the details, he did correctly identify orbital variations as a possible
cause of ice ages, prompting others to follow him with better and
more complete theories of the effects of orbital variations on the
climate of the earth.
See Imbrie and Imbrie (1979).
Abbreviation for Alternating Direction Implicit.
Involving or allowing neither gain nor loss of heat.
- adiabatic lapse rate
In the atmosphere, the rate of decrease of temperature which occurs
when a parcel of air rises adiabatically, i.e.
there is no heat transfer to or from the parcel. The adiabatic
lapse rate for dry air is -9.8 K/km.
Acronym for Asian Dust Input to the Oceanic System.
- adjustment time
A time scale characterizing
the decay of an instantaneous input pulse into a reservoir.
It is also used to characterize the adjustment of the mass
of a reservoir following a change in the source strength.
- Adriatic Sea
A part of the eastern basin of the
Mediterranean Sea located
between Italy and the Balkan Peninsula. It is landlocked on
the north, east and west, and terminates at the Otranto
Strait to the south. This is one of the two regions within
the Mediterranean where freshwater input exceeds evaporation
(the other being the Black Sea), a
a situation caused by outflow from the Po River.
The flow between the Adriatic and the greater Mediterranean
through the Otranto Strait is that of a typical
dilution basin wherein
low salinity water exits near the surface and high
salinity water enters at depth. There is an additional
outflow layer beneath the incoming
Levantine Intermediate Water (LIW) that results from the surface
water in the very shallow (less than 200 m) northern Adriatic
being greatly cooled by outbreaks of strong and cold winter
winds called bora. This gives the deep
outflow water, whose characteristics are a temperature of 13 C
and a salinity of 38.6, a density greater than that of the
See Buljan and Zore-Armanda (1976) and Tomczak and Godfrey (1994).
Acronym for Analysis of Dendrochronological Variability and Natural
Climates in Eurasia: The Last 10,000 Years, an EU project in which
the absolute dating control and seasonal growth of long tree-ring
chronologies will be used to reconstruct a range of climate variables
in different regions of northern Eurasia to enhance knowledge of
natural climate variability on a range of timescales within the
last 10,000 years and to advance understanding of the mechanisms
and forcings that generated this variability.
ADVANCE-10K Web site.
Acronym for Annual to Decadal Variability in Climate in Europe, a
project whose goals are: (1) to characterize as fully as possible the
variability of climate over greater Europe, including Iceland, the
Near East, and parts of North Africa, over the last 215 years; and
(2) to reconstruct the climate during the Late Maunder
Minimum (from 1675-1715).
ADVICE Web site.
Abbreviation for Arctic Environmental Data Directory, a repository
for information on the Arctic in support of the
Arctic Research and Policy Act of 1984. It contains
descriptions of data on global change studies, environmental
interactions, earth sciences, social sciences, and policy
and management. See the
AEDD Web site.
- Aegean Deep Water
See POEM Group (1992).
- Aegean Sea
A marginal sea in the eastern
Mediterranean Sea centered
at approximately 25 E and 38 N.
It is located between the Greek coast to the west, the
Turkish coast to the east, and the islands of Crete and
Rhodes to the south. It contains more than 2000 islands
forming small basins and narrow passages with very irregular
coastline and topography.
It covers an area of 20,105 km , has a volume of
74,000 km , and a maximum depth of 2500 m.
It is connected to the Levantine Sea
to the southeast via the Cassos Strait (67 km wide, 350 km deep)
between Crete and Karpathos, the Karpathos strait (43 km wide,
550 m deep) between Karpathos and Rhodes, and a
17 km wide and 350 m deep strait between Rhodes and Turkey.
It joins the Ionian Sea and
Cretan Sea to the southwest
through three wide passages between Crete and Antikithira
(32 km wide, 700 m deep), Antikithira and Kithira (33 km wide,
160 m deep), and Kithira and Peloponnese (11 km wide and 180 m deep).
There is considerable and complicated interchange of water
with the eastern Mediterranean through these passages.
provide a northern link to the
Black Sea from which the Aegean
receives around 190 km per year of water.
The surface circulation is most affected by the prevailing
northerly, cold and dry winds (called
Etesians and the low salinity
(from 26.2 in the summer to 35 in the winter) inflow from
the Black Sea. The winds cause upwelling along the eastern
coast, an east-to-west temperature gradient, intense convective
movements of surface water, and a southward flow along the
Greek coast. There is also evidence for a double gyre
circulation in the summer, anticyclonic in the east and cyclonic in the west,
and an overall cyclonic circulation in the winter with a northerly
current along the Asia minor coast and a southerly current along Greece.
The surface flow in the south has been found to be into the
Aegean between Kithira and Crete, Crete and Karpathos, Karpathos
and Rhodes, and Rhodes and Turkey, and into the Mediterranean between
Kithira and the Peloponnese coast.
The warm and saline intermediate waters originate in the Chios
Basin and feature a strong pycnocline
that inhibits vertical mixing. Deep water inflow from the
Mediterranean between 500-800 m between Antikithira and Crete
and between Crete and Karpathos is suggested by low salinity
The region around Rhodes is a source of
Levantine Intermediate Water (LIW), and the densest water
found in the Mediterranean has been
measured in the Mount-Athos Basin.
See POEM Group (1992).
Borne, deposited, produced, or eroded
by the wind. See Pye (1987),
Pye and Tsoar (1990) and Allen (1994).
A consolidated sedimentary rock consisting of
material deposited by the wind, an example of which is sandstone.
See Sellwood and Price (1994).
- Aeronomy Laboratory (AL)
A part of the ERL component of
NOAA that conducts research on chemical
and physical processes of the earth's atmosphere to advance the
capability to observe, predict, and protect the quality of the
AL Web site.
Abbreviation for Arctic Environmental Protection Strategy, a program
adopted by the governments of the eight circumpolar nations at the
First Arctic Ministerial Conference in Rovanierni, Finland in
June 1991. The objectives of the AEPS are to protect the Arctic
ecosystems; provide for the protection, enhancement, and restoration
of natural resources; recognize and seek to accomodate the traditional
and cultural needs of the indigenous peoples; regularly review the
state of the Arctic environment; and identify, reduce, and, finally,
to eliminate pollution. The programs established to meet these
objectives include AMAP,
PAME, EPPR, CAFE, and SDU.
AEPS Web site.
Acronym for Atmospheric Emitted Radiance Interferometer, a
Ground Based High Resolution Interferometer Sounder
(GB-HIS) which measures the downwelling atmospheric
emitted radiance at 0.5 cm spectral resolution in the
spectral range 3-18 um. It measures vertical temperature
and water vapor profiles, sea surface temperatures,
and cloud optical properties. See the
AERI Web site.
Acronym for Atmosphere/Ocean Chemistry Experiment.
The study of the atmosphere above about 50 km where
ionization are prevalent processes.
These are the non-gaseous microscopic particles and droplets floating
in the atmosphere that have a climate forcing effect just as do
the greenhouse gases.
They come from natural and artificial sources, with the most
abundant ones being particles of mineral dust, sulfuric acid,
ammonium sulfate, biological material-like pollens, and carbon
or soot. Aerosols provide forcing in a couple of ways, the
first being providing the nuclei around witch larger drops of
water can condense and release latent heat into the atmosphere.
They can also absorb or reflect energy radiated from the Sun
or Earth. It is not known at present whether their net effect
is to heat or cool the Earth.
Acronym for Airborne Experiment to Study Ozone Photochemistry,
an airborne chemistry study performed during the summer of 1994
by the Tropospheric Chemistry group of the
Aeronomy Laboratory (AL).
The NOAA Orion P-3, a midsize aircraft capable of measuring
through the planetary boundary layer (PBL) and the lower and middle
free troposphere, flew over the Denver and Nashville metropolitan
areas to make measurements needed to understand the processes and
sources of the ozone precursors that shape the distribution of
ozone. The compounds and quantities measured were O , NO, NO ,
PAN, NOy, NO/O , CO, SO and aerosols (with the latter
measured using the ASSP and
Abbreviation for actual evapotranspiration.
Abbreviation for Alternative Fluorocarbon Environmental Acceptability
- African Waves
A prominent meterological phenomena wherein waves originate over
central and western Africa and propagate westward into the eastern
Atlantic Ocean. They have wavelengths of around 2500 km, periods
of about 3.5 days and move with a westward speed of around
8 m/s. Their genesis begins with strong surface heating over
the Sahara during the northern summer combining with cooling of
the sea water over the Gulf of Guineau to the south to establish
a north-south temperature gradient over central and western
Africa. This gradient maintains the mid-tropospheric easterly
because of the associated easterly
thermal wind. The upper
tropospheric jet easterly jet stream and the southward extension
of the mid-latitude westerlies at the upper troposphere
sit above this. This combination causes the north-south
gradient of the absolute vorticity of the mean zonal wind to
change sign in the mid-tropospheric area that contains the
African Waves. This sign change is a necessary condition for
which provides a preferable environment for African Wave
See Wiin-Nielsen and Chen (1993).
Arctic Frontal Zone.
Acronym for Arctic Gas and Aerosol Sampling Program.
1. Abbreviation for Aspen Global Change Institute.
2. Abbreviation for the Atlantic Global Change Institute, established
at the BBSR to study global environmental
change, its probably consequences and especially the human
dimensions of change. See the
AGCI Web site.
Abbreviation for atmospheric general circulation model.
Aegean Deep Water.
- age and area theory
A theory advanced by the British ecologist J. C. Willis to explain
how the area occupied by a species is related to its population
as a whole. It is simply stated as: statistically speaking, the
area occupied by a species is directly proportional to its age
as a species, i.e. the longer it has had time to spread, the
further it will go. The practical applications of this theory
apparently leave something to be desired since, according
to Collinson (1988), ``this is an excellent example of
a logically satisfying theory which, unfortunately, so rarely
fits the facts that it cannot be supported in its original
- age of tide
The delay, usually a day or two, between full and
new moons (when the equilibrium semi-diurnal
tide is maximum) and the following
spring tides. This terminology
was first used to refer to this phenomenon by Whewell in
1883, although Defant referred to it as ``spring
retardation'' in 1961 and Wood later (in 1978) used the terms
``age of the phase inequality'' and ``age of the diurnal
equality'' to refer to, respectively, the ages of the
semi-diurnal and diurnal tides. This delay is caused
by frictional energy dissipation in coastal seas, although a
localized increase in the age of tide is also a good
indication of resonances at that location.
See Murty and El-Sabh (1985).
See double tide.
Abbreviation for Advisory Group on Greenhouse Gases, a
An animal in the superclass Agnath.
A superclass of the subphylum Vertebrata
of the phylum Chordata.
This has replaced the former class
Cyclostomata and includes
primitive, jawless vertebrates. Examples are lampreys, hagfish and
many fossil forms.
This class is also known as Marsipobranchii.
- agonic line
A line on a map that joins places where a magnetic compass points
true north as well as magnetic north, i.e. a line of zero
Abbreviation for the adjusted geosynchronous precipitation index technique
for adjusting geosynchronous
infrared data to remove known biases.
See Adler et al. (1994).
American Geophysical Union.
A condition observed annually in the coast water off Peru
in which the water is discolored red or yellow and there is
a significant loss of marine life. It typically occurs from
April through June and is probably caused by an increase
in water temperatures via the importation of warmer waters by
ocean currents. This causes the death of temperature sensitive
marine organisms such as dinoflagellates, which may in turn
kill other organisms via the release of toxins. The annual
nature of this phenomenon makes it distinct from the
El Nino phenomenon occurring in
the same region. This is also known as salgaso or
- Agulas Basin
An ocean basin located off the southern tip of Africa at
about 43 S in the South Atlantic Ocean.
It includes the Agulhas Abyssal Plain.
See Fairbridge (1966).
- Agulhas Current
The branch of the
western boundary current
in the Indian Ocean south of 30 S. This is one of the strongest
currents in the world ocean with mean speeds of 1.6 m/s throughout
the year and peak speds in excess of 2.5 m/s. It carries
95-135 Sv as it reaches the Agulhas Bank near 35 S.
When it encounters the ACC while rounding the
Cap of Good Hope, most of its transport turns back into the Indian
Ocean in a phenomenon known as the Agulhas retroflection.
This is largely due to the current developing instabilities and
shedding the eddies that result.
See Lutjeharms and van Ballegooyen (1988) and
Peterson and Stramma (1991).
- Agulhas Retroflection
See Peterson and Stramma (1991).
- Agulhas Return Current
See Peterson and Stramma (1991).
Acronym for Arctic Ice Dynamics Joint Experiment, a program that took
place in two phases in 1975-1976. In summer 1975 four manned camps
were maintained on ice floes in the Arctic Ocean to measure
surface and geostrophic winds, ocean current velocities, and
ice floe position. In April of 1976 the submarine USS Gurnard
traversed 777 nautical miles along three tracklines in the
Beaufort Sea, collecting ice
thickness data from upward-looking acoustical soundings.
AIDJEX Web site.
- air mass
In meteorology, a continguous and widespread body of air that
has been stagnant over a surface for a sufficient length of time
to have been modifed by the surface. An example would be a maritime
air mass that develops with high humidity over an ocean.
The formation of air masses is favored in regions of surface
high pressure regions due to the ambient light winds allowing the
long residence time necessary for modification. Given the
prevailing global circulation patterns, warm air mass formation
is favored at 30 latitude and cold air mass formation at
90 latitude, with the boundary between these two regions
being known as the polar front.
- Air Resources Laboratory (ARL)
A part of the NOAA ERL
network that performs studies related to climate and air quality
with research focused on turbulence and diffusion in the
atmosphere, global transport of pollutants, meteorology of
air pollution, air-surface exchange, and global climate change.
ARL Web site.
Acronym for Automatic Recording Inverted Echo Sounder.
Acronym for Atmospheric Integrated Research Monitoring Network, an
array of stations designed to detect the benefits of emissions
controls mandated by the Clean Air Act Amendments of 1990 and to
quantify these benefits in terms of deposition to sensitive
areas. This is a program of the
Air Resources Laboratory of
AIRMoN Web site.
Acronym for Atmospheric Infrared Sounder or Advanced Infrared
A side-looking imaging radar system which uses the synthetic
aperture principle to obtain high resolution images which
represent the radar backscatter of the imaged surface at
different frequencies and polarizations.
AIRSAR/TOPSAR Web page.
- Airy wave
A theory of waves of small amplitude in water of arbitrary
depth that is also known as linear wave theory.
The derivation of the theory, given the assumptions
of small wave slope ( ) and a depth much
greater than the wave height
( ), gives the expression for the water surface
where H is the wave height, k the wave number, and
the wave frequency. An expression for the wave
length has also been developed, although it must be solved
Simpler expressions are available for the limiting cases
of deep and shallow water, with deep water being the case
where (where h is the depth and
the deep water wavelength) and shallow water
the case where .
The particles move generally in closed elliptical orbits that
decrease in diameter with depth, reducing to limiting cases
of circles and straight lines in, respectively, deep and
See Kinsman (1984), LeMehaute (1976) and
1. Abbreviation for Airborne Imaging Spectrometer.
2. Abbreviation for Advanced Ionospheric Sounder.
- Aitken counter
A small expansion chamber used to measure the concentration of
CCN in the atmosphere.
See Riehl (1954).
Abbreviation for Arctic Ice Thickness Monitoring Project.
Arctic Intermediate Water.
Acronym for Arctic Internal Wave Experiment, a project of the
APL at the University of Washington that
took place in 1985. See also LEADEX.
- Ajax Expedition
An oceanographic research expedition from 1983-1984.
Acronym for Autonomous Lagrangian Circulation Explorer float,
an instrument that can be programmed to cycle up and down
through the water column at predetermined intervals to
provide vertical profiles of temperature and salinity.
See Davis et al. (1992).
Acronym for Atmospheric Laser Doppler Instrument.
- Aland Sea
A part of the Baltic Sea bordered by
the Gulf of Bothnia to the north,
the Gulf of Finland to the east,
and the man part of the Baltic Sea to the south.
- Alaska Coastal Current
A narrow, high-speed, westward flow which extends for more than 1000 km
along the coast of Alaska. This is a separate feature from
the offshore, deepwater
Alaskan Stream. It was not
recognized as such up until the mid-1970s when a series of
hydrocast surveys in the area was begun which led to its
identification as a distinct circulation feature.
The ACC is driven by freshwater discharge from the mountainous
and coastal regions around the Gulf of Alaska and the consequent
nearshore confinement of this low-salinity water by westward
winds. It is typically narrow (< 50 km), shallow (< 150 m)
and partially baroclinic.
It flows most intensely between 145 and 155 W through
the Shelikov Strait between the Alaskan Peninsula and
Kodiak and Afognak Islands, but extends
recognizably along the Peninsula as far as
The baroclinic speeds and transports have been
estimated as typically <30 cm s and
0.4 Sv, respectively, in the winter, spring and summer. In the
fall, when the freshwater influx leads to the spin-up of the ACC,
the speeds and transports have been estimated as
89-133 cm s and 1.0-1.2 Sv, respectively.
Current mooring measurements have yielded estimates of
six-month mean total transports ranging from 0.85 Sv at 151 W
to 0.64 Sv at 155 in Shelikof Strait, with daily means
as high as 2.5 Sv and marked variability from day to day.
This variability is thought to be mainly due to variations in
wind-forcing caused by the passage of large-scale storms along
the coast. The mean baroclinic transport as estimated from
the same measurements was found to be about 75% of the total.
See Stabeno et al. (1995).
- Alaska Current
The eastern limb of the counterclockwise-flowing subpolar gyre
in the North Pacific. This current is concentrated on the shelf
region by the freshwater input from Alaskan rivers which enhances
the pressure gradient across it. It is strongest in winter with
current speeds around 0.3 m/s and weakest in July and August when
prevailing winds tend to oppose its flow.
This current may or may not be distinguished from a western
boundary current flowing along the Aleutian Islands and called
the Alaskan Stream. Both have previously gone by the name of
Aleutian Current. Whether or not the nomenclature makes a
distinction, the Alaskan Stream and Current do have distinguishing
characteristics. The Current is shallow and highly variable while
the Stream is steadier and reaches to the ocean floor. The
more barotropic nature of the latter is evidence that it is
indeed a product of western boundary current dynamics while the
former is in an eastern boundary regime.
See Tomczak and Godfrey (1994).
- Alaskan Stream
See Alaska Current.
The proportion of incident radiation
reflected by a surface. About 30% of the incoming solar energy
is reflected back to space from the earth, of which 25% is reflected
by clouds and 5% by the surface or by atmospheric molecules or
suspended particles. The clouds and atmospheric gases and particles
absorb 25% of the incident radiation with the remainder absorbed at
the surface. See Peixoto and Oort (1992), Ch. 6.
The last of six ages in the
Early Cretaceous epoch, lasting
from 113 to 97.5 Ma. It is preceded by
the Aptian age and followed by
the Cenomanian age of the
Late Cretaceous Epoch.
- Alboran Sea
A part of the western basin of the
Mediterranean Sea that
extends from the Gibraltar Strait
in the west eastward to the Alboran Islands at about
3 W. It abuts the
Balearic Sea to the east.
See Fairbridge (1966).
Acronym for Arbitrary Lagrangian Eulerian.
Abbreviation for Atmospheric Lifetime Experiment/Global Atmospheric
Gases Experiment/Advanced GAGE. This is a program in which continuous
high frequency gas chromatographic measurements of two
biogenic/anthropogenic gases (methane and nitrous oxide) and
five anthropogenic gases (chlorofluorocarbons (3 types), methyl
chloroform, carbon tetrachloride) are carried out at globally
distributed sites. The program began in 1978 and is divided
into three parts associated with changes in instrumentation:
(1) the ALE part which used HP5840 gas chromatographs; (2) the
GAGE part which used HP5880 gas chromatographs; and (3) the
AGAGE part which uses a full automated system containing a
custom-designed sample module and HP5890 and Carle
Instruments gas chromatographic components. The
ALE/GAGE/AGAGE data are
available via CDIAC.
- Aleutian Current
See Alaska Current.
- Aleutian low
A center of action
centered over the Aleutian Islands between the east coast of the
Siberian Kamchatka Peninsula and the Gulf of Alaska at about
50 N. It is prominent in the winter and disappears in
summer, with the average central pressure below 1000 mb in
January. See Angell and Korshover (1974).
Acronym for AIDJEX Lead Experiment,
which took place Feb. 23 through Apr. 10, 1974 and investigated
small-scale meteorological and oceanographic processes
associated with leads in pack ice near Barrow, Alaska.
The experiment plan called for rapid deployment of five
instrumental huts, measuring equipment and personnel by
helicopeters and fixed-wing aircraft. The processes of
primary interest were sensible, latent, and radiant
heat loss to the atmosphere as well as the sinking of
convective plumes of saline water formed by freezing
and brine rejection at the surface. Logistical problems
limited the success of the experiment, with the
helicopter range limiting deployment to within 30
miles of Barrow and a dearth of suitable leads in that
Acronym for Long-life, multi-cycle, pop-up RAFOS floats.
- Alfred Wegener Institute (AWI)
The German national research center for polar and marine research.
The Institute was founded in 1980 and named after the geophysicist
and polar researcher Alfred Wegener.
The mandate of the AWI includes fundamental scientific research in
the polar regions, national coordination of polar research projects,
and logistic support of polar expeditions from other German
institutes. The Institute uses the RV Polarstern to perform
research at sea. See the
AWI Web site.
Acronym for Alaska Landscape Flux Study.
The common name for a division of primitive marine plants in which
the body shows little or no differerentation of the vegetative
organs, i.e. no true root, stem, or leaf. Algae also have no
true vascular system. This category includes
seaweeds as well as unicellular and filamentous organisms.
The study of algae is known as either algology or phycology.
- Algerian Current
A current that flows eastward along the Algerian coast in the
Mediterranean Sea. It flows
as a narrow, easily distinguished current for around 300 km
from about 0 to 4 E with a width of less than 30 km, average
and maximum velocities of 0.4 and 0.8 m/s, respectively, and
a tranport of about 0.5 Sv. This is a continuation of the
current associated with the
Almeria-Oran Front that is
itself a continuation of the
flow of Atlantic Ocean water entering through the
See Arnone et al. (1990)
and Tomczak and Godfrey (1994).
The study of algae. This is also known
A phenomenon encountered when sampling a continuous function to produce
values at discrete points. If the sampling frequency isn't high enough
to resolve the highest frequency signal present in the continuous
function, then the high frequency information above the sampling
frequency will appear as a false enhancement of (or, equivalently,
be aliased onto) a related lower frequency in the computed power
Acronym for Autonomous Lander Instrumentation Packages for
Oceanographic Research, a project funded by
MAST III to create a European fleet of
lander vehicles that can operate together in joint research
projects. Lander vehicles will be built to carry out a variety
of experiments ranging from sediment probes to fish tracking.
Three facets of lander technology are to be addressed: (1) the
development of techniques to launch a fleet of landers from
a single ship; (2) the development of new sensors for examining
processes in the water of the deep benthic boundary layer at depths
ranging from 200 to 5000 meters; and (3) the design and construction
of two new types of landers, i.e. one that can carry several sensing
devices and another compact one that can be operated from a small
See the ALIPOR Web site.
Common abbreviation for
A property of sea water operationally defined as the
excess positive charge to be balanced by CO3 and HCO3 ions.
The carbonate ion content of any unit of sea water is equal to
its alkalinity (i.e. excess positive charge) minus its total
dissolved carbon content.
See Broecker and Peng (1982).
- Allen's Rule
An ecogeographical rule, also known
as the proportional rule, extends
Bergman's Rule to include protruding
parts of the body such as necks, legs, tails, ears and bills, i.e.
such parts are shorter in animals that dwell in cooler regions.
This was established by Joel A. Allen in 1877.
- Allerod oscillation
A post-LGM European climate regime.
This refers to a period of general warmth between 10,000 and 9000 BC.
It was preceded by the Bolling oscillation
and followed by the Younger Dryas.
See Lamb (1985), p. 371.
The relationship between size and shape in an organism or object.
In heterochrony, if a particular structure
increases in size relative to the whole organism during
ontogeny, then the growth is said to show
positive allometry; if it decreases in relative size, then it
shows negative allometry. Increasing/decreasing the degree
of allometry is called peramorphosis/
The existence of the same state of more than one form of the same
element with different properties.
Of or pertaining to an unconsolidated, stratified deposit laid down
by running water. Occasionally applied only to fine sediments (e.g.
silt and clay), but more generally referring to coarser sediments
such as sand and gravel as well.
- Almeria-Oran Front
A front and an associated current that separate the fresher
water flowing in from the Atlantic Ocean via the Gibraltar
Strait from the saltier Mediterranean Sea water to the west.
The incoming water flows eastward as a jet, breaks into one or
two large eddies of around 150 km diameter, and then is deflected
to the right (the south) by the Coriolis force where it encounters
the African coast and continues flowing eastward as the
See Tomczak and Godfrey (1994).
- almost intransitive
In dynamical systems theory, a system is said to be almost intransitive if
it mimics transitive behavior for an indeterminate
period of time and then switches to an alternative resultant state
in the manner of an intransitive system.
Thus, different initial conditions may not only lead to different
resultant states, but also to eventual transitions between different
See Lorenz (1979).
Acronym for Arctic Lidar Observatory for Middle Atmospheric Research.
Acronym for Alpine Experiment.
Acronym for High Alpine Aerosol and Snow Chemistry Study, a
EUROTRAC project to study the deposition of acidity and aerosols
in the ecologically sensitive high Alpine regions. The
objectives were to determine the main physical and chemical
processes responsible for the occurrence and accumulation of
acidic and aerosol components in the high alpine region and to
investigate the contribution of various source regions to the
deposition of trace components and their geographical and
seasonal trends. This project was finished at the end of 1995.
ALPTRAC Web site.
A type of cloud shaped like heaps or piles and formed at an altitude
of approximately 22,000 feet.
A type of cloud that is grey or bluish striated and either fibrous
or a uniform sheet producing light drizzle. It is formed at an
altitude of approximately 23,000 to 24,000 thousand feet.
A deep submersible commissioned on June 5, 1964 at the Woods Hole
Oceanographic Institution. It has been used for over a thousand
research and rescue missions in the years since it was first launched,
most from aboard the tender ship Atlantis II, which was retired
from that duty in 1996.
ALVIN Web site.
Acronym for Amazonas Heat Source Experiment.
Acronym for Arctic Monitoring and Assessment Program, an international
organization established to implement certain components of the
Arctic Environmental Protection Strategy (AEPS) adopted by governments
of the eight circumpolar countries and the First Arctic Ministerial
Conference in 1991. The objectives of AMAP are to measure the
levels and assess the effects of anthropogenic pollutants in all
compartments of the Arctic environment. See the
AMAP Web site.
Abbreviation for Amazone Shelf Sediment Study.
- Amazon River
Acronym for the Amazon Biogeochemistry and Atmospheric Chemistry
Experiment, a supporting study for LAMBADA
that focuses on the consequences fo forest conversion, agriculatural
practice and abandonment, and secondary succession on regional and
global biogeochemistry and atmospheric chemistry. See the
LAMBADA Web site for further information.
- American Geophysical Union (AGU)
An international scientific society with over 31,000 members in
117 countries. It is dedicated to advancing the understanding
of the Earth and its environment in space and in making the
results known to the public. As such it publishes many journals
and books and sponsors frequent meetings.
See the AGU web site.
- American Meteorological Society (AMS)
An organization founded in 1919 to promote the development and
dissemination of information and education on the atmospheric and
related oceanic and hydrologic sciences. The journals published by
the AMS include ``Journal of the Atmospheric Sciences,'' ``Journal
of Applied Meteorology,'' ``Journal of Physical Oceanography,''
``Monthly Weather Review,'' ``Journal of Atmospheric and Oceanic
Technology,'' ``Weather and Forecasting,'' ``Journal of Climate,''
``Bulletin of the American Meteorological Society,'' ``Meteorological
and Geoastrophysical Abstracts,'' and the
AMS Web site.
Acronym for Antarctic Marine Ecosystem Research at the
Ice Edge Zone.
See Smith and Garrison (1990).
Abbreviation for Australian Monsoon Experiment, a program
of enhanced upper-air soundings and radar data collection in
northern Australia aimed at better documentation of those
large-scale weather patterns over Australia that are associated
with the ebb and flow of the Australian monsoon.
See Holland et al. (1986).
Abbreviation for Active Microwave Instrument.
- amino-acid dating
See Bradley (1985).
Acronym for Atmospheric Model Intercomparison Project,
a project to compare
the numerical results from a standardized simulation performed by over
30 modeling groups. AMIP is being coordinated by the
PCMDI on behalf of the WGNE
of the WCRP.
See Gates (1992) and the
AMIP Web site for further details.
Acronym for Advanced Microwave Imaging Radiometer.
Abbreviation for Acoustic Mid-Ocean Dynamics Experiment-Moving
Ship Tomography group.
See AMODE-MST Group (1994).
- amount effect
A term applied to the relationship between isotopic composition
and monthly rainfall where months with heavy rainfall show different
isotopic concentrations than do months with low rainfall. In
high rainfall months, rain frequency is higher which entails
a higher relative humidity
in sub-cloud air, hence less evaporation
from raindrops. Since the rate of evaporation determines the
isotopic concentrations (the greater the rate the higher the
heavy stable isotope composition), low rainfall months should
show a higher heavy stable isotopic composition than high rainfall
Abbreviation for Advanced Microstructure Profiler, an
instrument developed at the APL.
A stationary point around which tides rotate
in a counterclockwise (clockwise)
sense in the northern (southern) hemisphere, i.e. the
point about which the
cotidal lines radiate.
The vertical range of the tide increases with distance
away from the amphidrome, with the amphidrome itself
the spot where the tide vanishes to zero (or almost
This is also called an
See Fairbridge (1966).
- amphridomic point
A class of the Phylum
Mollusca of marine invertebrates.
These are commonly known as chitons and are flat,
benthic animals which creep along
the ocean bottom
using a broad, flat foot. All 630 or so known species
Abbreviation for Advanced Microwave Precipitation Radiometer, a total
power scanning multifrequency radiometer that collects data at
four frequencies while flying aboard the high altitude ER-2
research aircraft. See the AMPR Web site.
Acronym for Advanced Medium Resolution Imaging Radiometer.
Abbreviation for the Antarctic Meteorology Center, a research
group supporting the United States Antarctic Program with weather
and remote sensing data. See the
AMRC Web site.
Abbreviation for Alliance for Marine Remote Sensing, an international
nonprofit association founded in 1990
which develops and promotes marine applications
of remote sensing technologies. It owns and operates the
Center for Marine Remote Sensing located in Bedford, Nova Scotia and
publishes a newsletter called ``backscatter.''
AMRS Web site.
1. Abbreviation for
American Meteorological Society.
2. Abbreviation for Accelerator Mass Spectrometry, a method for measuring
long-lived radionuclides that occur naturally in the environment. It
uses a particle accelerator in conjunction with ion sources, large
magnets, and detectors to separate out interferences and count single
atoms in the presence of 1.E15 stable atoms.
Acronym for Advanced Microwave Sounding Unit.
Acronym for the Air Mass Transformation Experiment, a Japanese project.
See Lenschow et al. (1980).
- Amundsen Abyssal Plain
One of the three plains that comprise the
(the others being the
Plains). It is located at around 150 W.
- Amundsen Sea
A marginal sea of Antarctica centered at about
112 W and 73 S. It sits between the
to the east and
the Ross Sea to the west, with
the Antarctic Circle serving as the northern boundary.
See Fairbridge (1966).
Acronym for A Mediterranean Undercurrent Seeding Experiment.