Abbreviation for the Pacific/North American teleconnection pattern,
a triplet of North Pacific-North American circulation anomalies
thought to be connected to ENSO.
See Wallace and Gutzler (1981) and Horel and Wallace (1981).
Acronym for Pacific Northwest Coastal Ecosystem Regional
Study, a research program jointly sponsored by the
OCMP, the NMFS,
and the Oregon and Washington Sea Grant Programs. The purpose
of this program is to sponsor studies that will provide users
of coastal resources and management agencies with an improved
understanding of how coastal ecosystems in this region respond
to natural variability and human activities.
PNCERS Web site.
- P-N-J method
A wave spectrum method
for wave forecasting developed
by Pierson, Neumann and James (Pierson et al. (1955))
in the mid-1950s. Each wind velocity produces a certain range
of wave periods with a well-defined maximum, with the total
range of periods increasing with the wind velocity along with
the energy within the total spectrum. The
significant wave height
can be found with method along with the spectrum information.
See Komar (1976).
Abbreviation for Pacific Northwest Laboratory, a multi-program
national laboratory operated for the DOE by Battelle Memorial
Institute. Its mission is to conduct research and development
to meet national needs in energy, environment, the economy, and
national security. See the
PNL Web site.
Abbreviation for Programme National de Télédétection
Acronym for Polar Ozone and Aerosol Measurements.
Abbreviation for particulate organic carbon.
Acronym for Pacific Ocean Color Experiment,
POCEX Web site.
Acronym for Pilot Ocean Data System.
Acronym for Physical Oceanography of the Eastern Mediterranean.
See Malanotte-Rizzoli and Robinson (1988) and
Robinson et al. (1992).
Abbreviation for Polar-orbiting Operational Environmental
- Poincare wave
A gravity wave in a rotating system. One of the fundamental
wave solutions of the linearized barotropic equations. The
properties of these waves depend on how the wavelength compares
If they are short compared with the Rossby radius, then they are
ordinary nondispersive shallow-water waves (when the Rossby
radius is additionally large compared to the fluid depth).
If they are long compared with the the Rossby radius, the
frequency is approximately constant and equal to f or twice
the rotation rate. Gravity has no effect in this limit and
thus fluid particles move under their own inertia at the
inertial frequency f
and are called
The dispersion relation for Poincare waves is
is the square of the
horizontal wavenumber. (The use of this term is occasionally
restricted to those waves that satisfy the boundary conditions
for a channel.) See Gill (1982), pp. 196-197, 249-256.
- Poisson distribution
A statistical distribution that serves as a model for situations
concerned with the number of successes per unit of observation, e.g.
the number of phytoplankton caught per trawl.
More strictly speaking, this is a limiting form of the
when the probability of success for an individual trial
approaches zero, the number of trials becomes infinite,
and the product of these two quantities remains constant.
- Polar Air
Air originating in high latitudes, normally subdivided into
maritime polar air and continental polar air, according to the
nature of the surface over which it originated.
- polar circle
A parallel of latitude approximately 23 28' from either pole.
This is the angle between the tilted Earth and the
ecliptic. These circles were defined
by early geographers purely on geometrical grounds to divide the
surface of the Earth into zones, the polar circles ostensibly
separating the temperate and polar zones.
- polar domain
The northernmost of three hydrographic domains into which the waters
of the North Atlantic Ocean are sometimes divided for the purpose
of describing water mass formation in the region, with the other
two being (to the south) the arctic domain
and the Atlantic domain. The polar domain provides an
upper layer source water mass for the arctic domain that is
colder (< 0 C), less saline (30 to 34), and less
dense ( ranging from 24 to 27.6) than those from the
Atlantic domain. The low salinity of this surface water is derived
from both river runoff and through the melting of ice and it is
carried southward through the western Denmark Strait by the
East Greenland Current.
Small amounts of this water are carried eastward into the interior
basins of the arctic zone by the
Jan Mayen Current and the
East Icelandic Current.
See Swift (1986).
- Polar Front
In physical oceanography, a region of rapid transition in the
Southern Ocean between the
Polar Frontal Zone and
the Antarctic Zone.
The position of the PF is usually indicated by the large
temperature gradient along the temperature minimum of the
Antarctic Surface Water (AASW).
which starts to descend northward. The property indicators within
the front are < 2 along the -minimum at
Z < 200 m, a -minimum at Z > 200 m, and
> 2.2 along the -maximum at Z > 800 m.
The PF is one of three distinct fronts in the
Current, the others being the
Subantarctic Front (SAF) to the
north and the
Southern ACC Front (SACCF) to the
south. See Orsi et al. (1995).
- Polar Frontal Zone
In physical oceanography, the name given to a transition region in the
between the Subantarctic Front and the
identified as a region bound by the 3-9 C surface isotherms.
The PFZ is one of four distinct surface water mass regimes in the
Southern Ocean, the others being the
Subantarctic Zone (SAZ) to the north
Antarctic Zone (AZ) and
Continental Zone (CZ) to
See Orsi et al. (1995).
- polar halocline catastrophe
A hypothesized and modeled situation where the presently
dominant mode of thermohaline circulation is unstable and
evolves to a much weaker overturning circulation pattern.
See McWilliams (1996).
- Polar Intermediate Water
A water mass found in the
polar domain in the Northern
It is identified as a distinct temperature minimum layer
East Greenland Current
and has salinities in the range 34.4 to 34.7 and is colder
than 0 C. Since there is no sharp interface between
this and the upper
Arctic Intermediate Water,
it is distinguished chiefly by geographic location.
See Swift (1986).
- polar motion
The motion of the whole Earth relative to its axis of rotation.
It consists of two components, wobble
and polar wander, the former of
which is periodic and transient and the latter of which represents
the long-term trend of the migration of the Earth relative to
its spin axis.
See Gordon (1987).
- polar orbit
An orbit in which a satellite passes directly over or close to the
poles. The characteristic orbital period is around 90 minutes at
an altitude of between 500 and 1500 km. Such satellites are
usually Sun synchronoussunsynchronous, and have a field
of view such that it takes about 15 orbits to cover the globe, with
a specific location being seen about twice a day.
- polar wander
A polar motion caused by redistribution
of mass or angular momentum on or within the Earth and unrelated
to external torques (such as those that cause precession and
nutation). On a perfectly rigid Earth there would be no polar
wandering, and the angular momentum and angular velocity
vectors would coincide.
This is also known as true polar wander (TPW), as opposed to
the phenomenon called
apparent polar wander.
See Gordon (1987).
- Polar Water (PW)
Any water with salinity values less than 34.4 that enters the
arctic domain from the
polar domain in the North Atlantic.
The temperatures of POW are typicall low (< 0 C) although
they can reach 3 to 5 C in the summer.
The lowest salinities observed are summer salinities less than
30 in the
East Greenland Current.
The total transport of PW into the arctic domain is not well known
but usually estimated at around 1 Sv.
See Swift (1986).
- polarization relations
The relationships between the velocity components and pressure
for a progressive wave. They are found by substituting the
assumed wave form into the relevant equations.
See Gill (1982), p. 262.
Acronym for Polarization and Directionary of the Earth's
Reflectances, a wide field of view imaging radiometer that
will provide the first global, systematic measurements of
spectral, directional and polarized characteristics of the
solar radiation reflected by the earth/atmosphere system.
POLDER will better allow the radiation scattered in the
atmosphere from that reflected by the surface. The data
will be processed to determine the physical and optical
properties of aerosols so as to classify them and study
their variability and cycle; improve the climatological
description of certain physical, optical and radiative
properties of clouds; precisely determine the influence of
aerosols and clouds on the earth's radiation budget; and
quantify the role of photosynthesis from the continental
biosphere and oceans in the global carbon cycle.
It will fly on the
ADEOS mission and the results will
contribute to the WCRP and
POLDER Web site.
Acronym for Polar Exchange at the Sea Surface, a component of the
NASA EOS program that investigates the
exchange of mass and energy at the air-ice-ocean interface in the
polar regions. See the POLES Web site.
- poleward energy flux
The flux process on Earth made inevitable by the fact that more
heat is incipient on and absorbed at low than high latitudes
and that the Earth is surrounded by a fluid envelope.
This excess heat then moves from the tropics to
the poles in both hemispheres, i.e. down the gradient, via the
atmosphere and the oceans. The partitioning of this flux
between the atmosphere and the oceans is as yet not well estimated.
If there were no fluid envelope on the Earth, then the tropics
would be much warmer and the poles much colder.
Acronym for Polar Experiment, a FGGE
- pollen-climate response surface
See climate space.
In phytogeography, this is
said of plant taxa that occur in two
or more phytochoria. These are
also called ``liaison taxa''.
See Collinson (1988).
- polyclimax hypothesis
An extension of the
monoclimax hypothesis that
introduced the idea that several climax types could occur in a
uniform climatic regime, especially in relation to soil or
See McIntosh (1978).
An oceanographic program to measure the eddy currents in the North
Atlantic Equatorial Current for several months using moored current
meters and hydrographic surveys. This was a program carried out in
1970 by the Soviet Union.
See Brekhovskikh et al. (1971).
A joint US/USSR oceanographic program to study mesoscale processes
in the North Atlantic in the late 1970s and early 1980s.
It included a Synoptic Dynamical Experiment (SDE), a Local
Dynamics Experiment (LDE), and a statistical geographical experiment.
The field phase of POLYMODE ended in 1979.
An oceanic area which remains either partially or totally ice free
at times and under climatological conditions where the surface
waters would be expected to be ice covered.
They appear in winter when air temperatures are well below
the freezing point of sea water and are bordered by water that
is covered with ice.
They are typically rectangular or elliptical in shape and
occur quasi-continuously in the same regions.
The size of polynyas can range from a few hundred meters to
hundreds of kilometers.
Polynyas are of interest for several reasons. They are sites
for active brine formation which may affect the local water density
structure and current field and may also influence large-scale
water mass modification. They are also a locus for gas exchange
between the ocean and atmosphere in polar regions. The large
sensible heat fluxes (along with fluxes due to
evaporation and longwave radiation) tend to dominate regional
They are also of biological interest since their regular occurrence
makes them important habitats, e.g. the open water can lead to
localized plankton blooms and large mammals tend to use them as
There are two mechanisms for polynya formation. In the first
ice may form within a region and be continually removed by
winds, currents, or both. Here the heat required to balance
loss the atmosphere and hence to maintain the open water is
provided by the latent heat of fusion of the ice being
continually formed. The second mechanism involves oceanic
heat entering a region in quantities sufficinet to prevent
local ice formation. The first mechanism creates
``latent heat polynyas'' and the
second ``sensible heat polynyas'', and both mechanisms may
operate simultaneuously in the same region.
See SMith et al. (1990).
Abbreviation for Particulate Organic Matter. This is usually
split into large (or sinking) POM and small (or suspended)
POM. Large POM is typically greater than 50 m in diameter,
sinks at rates around 100 m/day, and is usually sampled with
sediment traps. It consists mainly of
marine snow, zooplankton fecal
pellets and intact organisms.
Small POM is typically between about 1 and 50 m in
diameter, sinks very slowly (if at all), and is sampled by
filtering sea water.
See Najjar (1991).
Acronym for Polar North Atlantic Margins, an LESC program to
investigate the Late Cenozoic evolution of the Polar North
Atlantic Margin. This project features scientists from
seven European nations studying the major climatic variations
over the last 5 million years and their impact on the environment
in European Arctic regions during a period when glacial cycles
dramatically changed the landscape and depositional environment
along the Polar North Atlantic margin.
The program studied the long-term climatic signal documented in
the marine sediment fans deposited adjacent to glacially
overdeepened fjords and shelf troughs, the latest
interglacial-glacial cycle by absolute dating and
high resolution stratigraphic work to obtain environmental
parameters such as ice distribution and oceanic circulation
patterns, and the present-day interglacial setting as an
interpretational tool for studying the glacial-interglacial
sedimentary record with emphasis on sediment transfer
processes. See the
PONAM Web page.
A westerly wind blowing in the Mediterranean area.
Abbreviation for principal oscillation patterns. In linear
cases, PIPs reduce to damped normal modes
or POPs, that represent the eigenoscillations of the reduced
linear dynamical system.
See Hasselmann (1988) and Hasselmann (1993).
- population biology
The tidal boretidalbore of the Amazon River.
Physical Oceanographic Real-Time System.
- positive feedback
A type of feedback in which a perturbation to
a system causes an amplification of the process, and thus enhances
itself. An example is the
- Postglacial Climatic Optimum
See Atlantic period.
- potassium-argon dating
A radioisotopic dating method
based on the decay of the radioisotope K (potassium)
to a daughter isotope Ar (argon).
This has been used to date sea-floor basalts as well as
to provide the accurate dating needed to establish and correlate
on a world-wide basis the geomagnetic polarity time scale.
It has also seen limited use in dating lava flows juxtaposed
with glacial deposits, thus enabling the glacial event to be dated.
The K decays into both Ar and Ca with a
half-life of 1.31 years, although the relative
of abundance of the latter precludes its use for dating purposes.
Rocks of volcanic origin are dated using this method
since argon is driven off by heating which leaves the samples
argon free as they initially cool. The K builds up over
time as the potassium decays until it is heated, released,
and measured in the laboratory. The K content is derived
from a measurement of the total potassium content or by measurement
of another stable isotope, K, since the abundance ratios of the
potassium isotopes are known. The potassium and argon measurements
have to be made on different parts of the same sample, which
led to the development of the
method. The extremely long half-life of the argon restricts the
use of this procedure to samples greater than 100,000 years old, with
volcanic rocks formed over the last 30 million years the most
common specimens dated.
This dating method assumes that no argon was present in the material
after formation and that the system remains closed from the
time of formation. The first assumption can be violated in the
case of the formation of deep-sea basalts which retain argon during
formation under high hydrostatic pressure, and some material can
retain argon from argon-rich source materials during formation.
This can result in an overestimation of the sample age.
The second assumption can be violated when argon is absorbed
on to the surface and interior of a sample, although the degree
of atmospheric concentration can be adjusted using known
atmospheric isotopic argon ratios.
See Bradley (1985).
- potential evaporation
The amount of water that would be evaporated from a land or water surface
if the water supply were unlimited, as opposed to
actual evaporation. The latter will
fall below the former when the water at the evaporating surface is
- potential evapotranspiration
The theoretical maximum amount of water vapor that can be convyed
to the atmosphere by the combined processes of evaporation and
by a surface covered by green vegetation with no lack
of available water in the soil.
- potential density
A physical oceanographic term for the density of a sample calculated
from its salinity,
and at a selected pressure, i.e.
This is the effective density of
a parcel of water after removing the heat associated solely with
the effects of compression. Up until about 1970
calculations of potential
density values were routinely performed with
atmospheric pressure at the sea surface as the selected pressure,
but later investigators found it sometimes convenient
to instead calculate
potential densities at other pressure levels. The 4000 dbar pressure
level (abbreviated )
is probably the next most often used level. Other levels
(usually at 1000 dbar increments)
are also sometimes used and similarly
- potential surface
See geopotential surface.
- potential temperature
A physical oceanographic term for the temperature that a water
sample gathered at depth would potentially
have if brought adiabatically (i.e.
without thermal contact with the surrounding water) to the surface,
i.e. the effective temperature of a water parcel after removing
the heat of the parcel associated solely with compression.
A sample brought from depth to the surface will, due to the slight
compressibility of sea water, expand and therefore tend to cool,
and as such potential temperatures at great depths are always less
than measured temperatures.
In meteorology this is defined as a measure of temperature that
removes the effects of dry adiabatic temperature changes experienced
by air parcels during vertical motion. This can be calculated
where is the potential temperature,
a reference pressure, the gas constant for
dry air and the specific heat.
- potential thickness
In physical oceanography, a quantity equal to the local
thickness of a water layer divided by the local sine of
See Stommel (1987).
- potential vorticity
In the simplest case, this is
a quantity equal to
barotropic fluid (or at least in
a fluid layer of constant density within a larger body of fluid) where
is the relative vorticity,
f the planetary vorticity, and
D the depth. This relation permits predictions to be made
about how vorticity will change in a column or parcel of water
if it moves northward or southward or into shallower or deeper
water, assuming that frictional processes are negligible.
More general and complicated versions of this quantity can
be defined, but this simplest case well illustrates the essential
physical processes without confusing the issue.
See Bryan (1987).
The rate of doing work. It is measured in units of
joules per second (J/s) and expressed in watts (W)
where 1 W = 1 J/s. The fps unit of power is the
horsepower, a rate of working equal to 550 ft-lbf per second.
Conversions are: 1 horsepower = 745.7 W; 1 W = 10 erg/second.
- power spectrum
The presentation of the square of the amplitudes of the harmonics
of a time series as a function of the frequency of the harmonics.
Abbreviation for parts per billion.
Abbreviation for parts per million.
1. Abbreviation for principal prediction patterns, used synonymously
2. Abbreviation for Pool Permutation Procedure, a method for testing
the significance of difference in the means, temporal and spatial
variances, and spatial patterns between two data sets. See
Preisendorfer and Barnett (1983).
- Practical Salinity Scale
In oceanography, a scale on which the salinity of
ocean water is evaluated. It is a unitless scale that was
developed to unify two separate salinity determination methods
that were previously used for laboratory and in-situ measurements.
The results are reported in a unitless manner since it is based on
chlorinity ratios rather than
measurements of absolute quantities, although the results are
mostly consonant with earlier ones reports in units of parts
See Lewis (1980).
- Practical Temperature Scale
A temperature scale created to provide an operational method
for measuring temperatures that is precise and reproducible.
See Comite International des Poids et Measures (1969).
- Prandtl number
A dimensionless number expressing the ratio of
the Peclet number to
the Reynolds number.
It is expressed by
where Pe is the Peclet number, Re the Reynolds number,
the kinematic viscosity, and
the thermal diffusivity.
When Pr = 1, the viscous time scale is equal to the time scale
of thermal diffusion, and similarity exists between viscous dissipation
and thermal diffusion. The Prandtl number is equal to about 0.7
for air, and is about 13 at 0 C and 7 at 20 C for water.
See Kraus and Businger (1994), p. 33.
Acronym for Precise Range and Range Rate Experiment, which ran
Abbreviation for Paleoclimate Reconstruction for Climate
- Pre-Boreal period
A post-LGM European climate regime. This refers
to a renewed rise of temperature setting in about 8300 BC that led
to the sustained warm climates of post-glacial times.
It was preceded by the Younger Dryas and
followed by the Boreal period.
See Lamb (1985), p. 371.
All of geologic time
before the Phanerozoic eon, i.e. about
Also called precession of the equinoxes, this component (the other
two being eccentricity and
obliquity) of the orbital perturbations
that comprise the Milankovitch theory
is actually two components. The first is axial precession, where
the earth's axis of rotation wobbles likes a spinning top due to
the torque of the sun and the planets on the non-spherical earth.
Therefore the North Pole describes a circle in space with a period
of 26,000 years. The second is elliptical precession in which the
ellipse that is the earth's orbit is rotating about one axis.
Both effects combined are known as the "precession of the equinoxes"
where the equinox (March 20 and September 22) and solstice
(June 21 and December 21) shift slowly around the earth's orbit
with a period of 22,000 years. The eccentricity modulates and splits
the precession frequency into periods of 19,000 and 23,000 years.
The precession causes warm winters and cool summers in one hemisphere
and the opposite in the other, with the effect being largest at the
equator and diminishing towards the poles.
- precipitable water
The total mass of water in a vertical atmospheric column of unit
area, or its height if condensed in liquid form.
The repeatability of an instrument, measured by the mean deviation
of a set of measurements from the average value. Contrast this to
accuracy. As an example of the difference,
an instrument can measure a quantity a hundred times and if all
the measurements are within a percent of each other it is a
precise instrument, but if it has measured the correct value
as, say, twice the correct value every time then it is not an
accurate instrument or, alternatively, it is precisely wrong.
- predictability of the first kind
The prediction of sequential states of the climate system at fixed
values of external parameters and assigned variations of initial
See Lorenz (1975) and Kagan (1995).
- predictability of the second kind
The prediction of an asymptotically equilibrium response (of the
limiting state) of the climatic system to prescribed changes in
See Lorenz (1975) and Kagan (1995).
In heterochrony, this is a type of
peramorphosis that involves the earlier
onset of growth of a specific structure, which allows a longer
period of growth and development.
- pressure broadening
In atmospheric radiative transfer,
a process by which the broadening of
is brought about by collisions between molecules or atoms, which can
supply or remove small amounts of energy during radiative transitions,
thereby allowing photons with a broader range of frequencies to
produce a particular transition of a molecule. This is the primary
broadening mechanism in the
- pressure coordinates
A vertical coordinate system often used in numerical circulation
models in which the vertical coordinate is pressure. The equations
are created by replacing the vertical velocity in the equations of
motion with the total derivative of the pressure following the
- Prestwich, Joseph (1812-1896)
See Peterson et al. (1996), p. 96.
A method for dealing with nonstationarity in time series
analysis where a new series is creating by forming the
differential of the original series. In practice this is
done by taking the difference between successive points in
the original series, although to be strictly correct this
should be done between successive midpoints. This procedure
removes both the trend and low-frequency components of the
original series while retaining information about the
short-variance. Another method for dealing with this problem
See Burroughs (1992).
The last of four ages in the
Eocene epoch (coincidental with the
Late Eocene), lasting from 40.0 to 36.6 Ma. It is preceded by
the Bartonian age and followed by
the Rupelian age of the
- primary aerosol
One of two categories of atmospheric aerosols as classified
by formation process, the other
being second aerosols.
Primary aerosols are due to direct emission of particulate
material into the atmosphere from both anthropogenic
(e.g. urban/industrial process, land use practices) and
natural (e.g. volcanism, wind-blown dust, sea-spray) activities.
See Pueschel (1995).
- primary productivity
The amount of organic material produced by organisms from
inorganic material. Most of the primary production in the
oceans is due to
in the upper 100 m, i.e. the
See Fogg (1975).
Acronym for the Purdue Rare Isotope Measurement Laboratory, a dedicated
research and service facility for AMS. See the
PRIME Web site.
- primitive equations
A set of filtered equations obtained
from the fundamental equations of motion of a fluid
by applying the
and neglecting the viscosity.
They comprise three
prognostic and three diagnostic
equations, the former of which are the x and y (or horizontal)
components of the momentum equation and the thermodynamic equation
of energy, and the latter the continuity equation, the hydrostatic
equation and the equation of state. These equations form a closed
set in the dependent variables
which are the three components of
velocity, pressure, density and temperature. The PEs filter out
vertically propagating sound waves.
- primum mobile
A theory of literally a ``first mover'' expostulated by
Aristotle that was used to explain a perceived general
broad pattern of westward flow in the world oceans.
The first mover, a theological being, was itself unmoved
but acted on the circumference of the universe to cause it to move.
The theory asserted that the shape of heaven is spherical
and it encloses successively smaller spheres down to the
center, i.e. earth, with the motion of the
outermost sphere being uniform and
that of the inner spheres increasingly irregular as the center
was approached. Since the sun and stars appeared to move to the
west and they were in an outer sphere, the first mover must be
moving things in that direction and therefore
the motion of the seas
should be generally to the west, although more irregular.
This theory and the consequent belief in general westward
motions in the seas held sway for many centuries until the
weight of observational evidence made it untenable.
See Peterson et al. (1996).
- Prince Henry the Navigator (1394-1460)
The third surviving son of Portugal's King John I who,
to help attain his goals of conquest and the conversion of
pagans to Christianity, founded what some have called the
first modern school of oceanography in the town of Sagres.
He summoned seamen, cartographers, astronomers, shipbuilders
and instrument makers from all over Europe to engage in
activities that would provide a large part of the foundation
for the European exploration of the world. His efforts
earned him the surname the Navigator.
Significant advances initiated by the school included the
systematic keeping of logbooks and annotation of charts,
replacing the astrolabe with
the quadrant, and the development
and construction of the Portugeuse caravel as a durable ship for
long voyages of exploration. Although Henry (who never
participated in any significant voyages himself) did manage
to convince someone (Gil Eannes) to sale beyond the
Cape of Bojador (on the western Sahara coast southeast of the
Canary Islands) in 1433, his men did not cross the equator
in his lifetime.
See Peterson et al. (1996).
A Russian remote sensing module (named for the Russian word for
nature) planned to provide the experimental basis for a scientific
research program for the development and verification of remote
sensing methods and investigations of regional and global problems
in climatology, oceanography, and ecology. The module
carries optical and infrared scanners, an imaging spectrometer,
a LIDAR, scanning and pointing
microwave radiometers, SAR, and high
resolution digital (stereo) cameras. The launch data for
PRIRODA is March 1996 and the operation is expected to
cover 1996-97. This mission is conducted by the
Russian Space Agency (RKA).
PRIRODA Web site.
The Pliocene Research, Interpretation,
and Synoptic Mapping Project, the goals of which include providing
modelers with improved quantitative global paleoenvironmental information
associated with the warm climates of the Pliocene and providing a
forum for data and modeling experts to collaborate in establishing what
boundary conditions are needed, planning model experiments, and
interpreting and evaluating model results. See
Dowsett et al. (1994) and the
PRISM Web site.
- probability density function
A function whose integral from A to B (with A less than or equal to
B) gives the probability that a corresponding
random variable assumes a value
on the interval from A to B. Probabilities are given by
appropriate areas under the curve representing this function.
- probability distribution
A function which assigns a probability to each value within the
range of a discrete random variable.
There are many different types of distributions used for
varous purposes, examples of which include
This is also known as a probability function.
Acronym for Pilot Radiation Observation Experiment, a part of the
ARM program designed to provide a tropical cloud and
radiation data base for ARM, a testbed for ARM instrumentation in
the tropics, and experience for a long-term ARM observational facility
to be established in the tropical western Pacific. See the
PROBE Web site.
Acronym for Processes and Resources of the Bering Sea Shelf.
Acronym for Processes in Regions of Fresh Water Influence, a project
whose overall aim is to develop process understanding and tested
numerical models for regions of freshwater influence (i.e. ROFIs).
This EC MAST project studies the role of
the physical processes controlling water property distributions and
the role of
suspended sediments in controlling the availability of light,
nutrients, and phytoplankton growth. See the
PROFILE Web site.
In numerical modeling, an equation is prognostic if the future value
of a dependent variable
is predicted from the present value(s) of one
or more dependent variables.
Acronym for Pre-Operational Modeling int he Seas of Europe, a project
whose primary objective is to optimize the application of existing
dynamical models of the North Sea such that the rates and scales of
sediment exchange between the coast and the nearshore zone can
be quantified for management applications.
PROMISE Web site.
The second of two eons in the
Precambrian period, lasting from 2500 to 570 Ma.
It is preceded by the Archean eon and
followed by the Phanerozoic eon, and
is comprised of the Early (2500-1600 Ma), Middle (1600-900 Ma),
and Late (900-570 Ma) eras. It is characterized by the earliest
forms of life on earth.
Acronym for Profile Telemetry of Upper Ocean Currents, a
NOAA PMEL project to develop a real-time
capability for satellite transmission of ADCP
data from deep water surface moorings. The first PROTEUS mooring
was successfully deployed in April 1990 at 0 ,
140 W as part of the EPOCS program.
See McPhaden et al. (1990).
An animal phylum of unicellular, eukaryotic
most important groups of which for paleoclimatology are
Protozoa range in size from 0.1 mm to 8 cm.
Some classification systems group the Protozoa with other
simple eukaryotic organisms in the kingdom Protista.
- Proudman-Taylor theorem
See Taylor-Proudman theorem.
- proxy data
Paleoclimate data inferred indirectly
via the use of transfer functions.
The underlying idea is that organisms exhibit a high degree of
differentiation according to their physical environment, and that
physical variables can be estimated from biotic distributions once the
degree of relationship has been objectively established. For example,
some present plankton species live in cold waters and others prefer
warmer waters. If we make the additional assumption that fossil
assemblages of these species (or their related ancestors) exhibited
similar temperature tendencies, then we can infer, within limits,
the temperature of the water in which they existed. See
Crowley and North (1991), Appendix B.
Compare to instrumental data.
Abbreviation for Profiling Reflectance Radiometer.
Phycological Society of America.
Abbreviation for Polar Stratospheric Clouds, a type of cloud
first identified by McCormick et al. (1982).
They are thought to exist in two primary categories: Type I, composed
of nitric acid-water particle that are stable at temperatures
above the frost point; and Type II, composed of water ice crystals
that are stable at sub-frost point temperatures. Both PSC types
are efficient sies for heterogeneous reactions that activate
chlorine radicals from normally benign reservoirs and, at the
same time, sequester odd nitrogen species such as less reactive
HNO3. These reactions prime the polar stratosphere for
chlorine-catalyzed ozone depletion, a process that can be quite
rapid and severe if the PSC particles involved grow large enough to
undergo sedimentation and irreversibly remove the sequestered
See McCormick et al. (1993).
A mineral whose outward crystal form is that of another species.
It has developed via some type of
transformation (alteration, substitution, incrustation, or
paramorphism) and is described as being ``after'' the mineral
whose outward form it has.
A projection serving as a foot. Literally, a false foot.
- pseudospectral method
In numerical modeling, an approximation which uses interpolating
functions to estimate derivatives of fields represented on a grid
in physical space. It is so-called because the interpolating
functions used are usually the same as are used in the
spectral method. All operations
other than differentiation are carried out in the physical space
defined by the grid rather than in spectral space. This allows,
for example, the calculation of the nonlinear terms, a dauntingly
onerous task in spectral space, to be easily performed. The
trade-off is that the calculations are
aliased, although various remedies for
the problem have been proposed.
See Gottlieb et al. (1984).
Abbreviation for Permanent Service for Mean Sea Level, an archive
based at the Proudman Oceanographic Laboratory which contains monthly
and annual mean sea level information from over 1600 tide gauge
stations from around the world. See the
PSMSL Web site.
The study of the physical and thermodynamic properties of the
atmosphere. The properties mainly of concern are
relative (or percent) humidity,
enthalpy (or total heat),
density and pressure.
- psychrometric chart
A chart on which various physical and thermodynamic properties
of the atmosphere are plotted to ascertain their various
One of two regions into which the ocean depths are sometimes
divided according to temperature, the other being the
thermosphere. The psychrosphere
is those ocean depths where the temperature is less than
10 C, which can range anywhere from 100 to 700 m
beneath the surface depending on oceanic conditions.
This coincides with the
- pteropod ooze
Ooze composed of the shells of small, planktonic swimming molluscs
with a calcareous shell that live in tropical and subtropical
waters. These are coarser than
globigerina oozes, are found
between 1500-3000 m depth and cover no more than 1% of the
See Tchernia (1980).
- Purdy, John (1773-1843)
See Peterson et al. (1996), p. 59.
Abbreviation for Profiling Ultraviolet Instrument.
Abbreviation for Polar Water.
In physical oceanography, a layer where density changes most rapidly
with depth. It can be associated with either a
thermocline or a
In physical oceanography, a layer where the vertical change of density
is very small and displays a local minimum.
An instrument for measuring either the diffuse or the total global
An instrument for measuring the longwave atmospheric radiation or the
outward radiation from the Earth's surface.
An instrument for measuring direct solar radiation, excluding the
diffuse and reflected components.
A Phylum of phytoplankton that
are a large group of very diverse pigmented or colorless
unicellular organisms possessing two flagella which differ
in structure and position according to species.
Extensively studied are the dinoflagellates, most of
which are encased in a cellulose wall sculptured into
patterned plates. Most dinoflagellates are phototrophic and
reproduce by cell division, although some can also live