- Abbreviation for the Pacific/North American teleconnection pattern,
a prominent mode of low frequency variability in the extratropics of
the northern hemisphere. It appears in all months except June and
July, and reflects a quadrapole pattern of height anomalies.
Anomalies of similar sign are found south of the Aleutian Islands and
over the southwestern U.S., while those with opposite sign are located
near Hawaii and over the intermountain region of North American (central
Canada) during the winter and fall (spring).
The spatial scale of the PNA is largest in winter, when the Aleutian
center covers most of the northern latitudes of the North Pacific.
It contracts in the spring
when the subtropical center near Hawaii reaches a maximum.
It disappears in June and July and reappears in the late summer and
fall. During this period, the midlatitude centers are dominant
and appear as a wave pattern emanating from the eastern North
The PNA pattern shows substantial interseasonal, interannual and
See Wallace and Gutzler (1981) and Horel and Wallace (1981).
- 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 particulate organic carbon.
- Acronym for Pacific Ocean Color Experiment,
POCEX Web site.
- Acronym for Physical Oceanography Distributed Active Archive
Center, an element of
EOSDIS and located at JPL,
is responsible for archiving and distributing data relevant to the
physical state of the ocean.
Most of the data archived at PODAAC is derived from sensors on
- 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).
- A free-fall vertical velocity profiler.
POGO is an acoustically-tracked dropsonde intended to measure the
depth-averaged horizontal velocity from the sea surface to some
See Rossby et al. (1991).
- Acronym for Partnership for Observation of the Global Oceans, an
international network of major oceanographic institutions established
to promote the integration and implementation of global oceanographic
- 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.
- 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 (PF)
- In physical oceanography, a region of rapid transition in the
Southern Ocean (SO) between the
Polar Frontal Zone (PFZ) and
the Antarctic Zone (AZ).
The position of the PF is usually indicated by the large
temperature gradient along the temperature minimum of the
Antarctic Surface Water (AASW).
where it starts to rapidly descend northward.
The PF is the northern boundary to cold (1.5 to 2C)
near-surface water formed by winter cooling, i.e.
the Antarctic Surface Water.
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 (ACC), the others being the
Subantarctic Front (SAF) to the
north and the
Southern ACC Front (SACCF) to the
This has previously been referred to as
the Meinardus Line (1926),
the Oceanic Polar Front (1928),
the Antarctic Convergence (1933) and
the Antarctic Polar Front (1960).
See Orsi et al. (1995),
Belkin and Gordon (1996),
Peterson and Stramma (1991) and
Moore et al. (1999).
- Polar Frontal Zone
- In physical oceanography, the name given to a transition region in the
Southern Ocean (SO) or
Antarctic Circumpolar Current (ACC)
between the Subantarctic Front (SAF)
to the north and the
Polar Front (PF) to the south.
This was first called the
Antarctic Polar Front Zone in the
mid-1970s but later modified to the present name.
identified as a region bound between 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 Front Survey
- An investigation in the North Atlantic
that took place during IGY under the
auspices of ICES.
See Dietrich (1969).
- 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 (PIW)
- 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 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 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 PW are typicall lowy ( 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).
- A GPS-navigated ocean acoustic current profiler.
See Leaman et al. (1995).
- 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.
- POLE Experiment
- See Davis et al. (1978) and
Simpson and Paulson (1979).
- 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.
See also Barry et al. (1993).
- 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.
- Poleward Undercurrent (PUC)
- A current that flows from Peru to northern and central Chile over
the slope and outer shelf, and is identified by a subsurface maximum.
According to Strub et al. (1998):
The Poleward Undercurrent is clearly identified by its water mass
characteristics. At a given location it is saltier, richer in nutrients
and lower in oxygen than the surrounding water. Maps of salinity at
approximately 150 m depth and of the minimum value of oxygen found
beneath 50 m depth depict its path within 100 km of the coast from
20S to approximately 42S. Alongshore sections of
salinity next to the coast from 15 to 42S reveal a tongue
of high salinity between 100 and 300 m depth, spreading from north
to south, descending from 150 m depth north of 20S to 200-300 m
depth south of 25S. It has been traced to 48S using
geostrophic velocities and T-S characteristics.
The Poleward Undercurrent is also evident in onshore-offshore sections
of geostrophic velocity from hydrographic cruises.
A section of mean, north-south geostrophic velocities shows it to
be maximum over the continental slope at 150-200 m depth. Off Chile at
30S, hydrographic sections made in each season in 1991-1992 show
it within 40 km of the coast, often extending to the surface.
Consistent with the values of these geostrophic velocities, direct
measurements of velocities from shipboard profiling current meters
and parachute drogues have found values ranging from
0.1 to 0.5 m s a depths of 100-300 m.
This has also been called the
Gunther Current (after
Gunther (1936)) and the
See Wooster and Gilmartin (1961) and
Strub et al. (1998).
- Acronym for Polar Experiment, a FGGE
- 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.
The seven intensive hydrographic surveys of temperature, salinity and
oxygen of the LDE took place between May 15 and July 15, 1978 and were
carried out in a 200 km wide octagonal region centered at
3105'N, 6930'W, a location within the southern portion
of the Gulf Stream recirculation region.
The recirculation region is a northwestern intensification of the
wind-driven subtropical gyre in the North Atlantic.
The location was chosen as a compromise among a desire to work well within
the gyre, with its associated large m ean and eddy currents, a conflicting
desire to avoid the peculiar measurement problems associated with
especially intense currents, such as those of Gulf Stream rings, and
a desire to use the familiar MODE results
(from 28N, 70W) as a basis for LDE experimental design.
The LDE was designed to meet five scientific objectives:
See McWilliams et al. (1983) and
Taft et al. (1986) (and several other related papers in the
same issue as the latter).
- to design sampling schemes to yield estimates of the various
components in the dynamical balance equations for mesoscale eddies, i.e.
to demonstrate the degree of potential vorticity balance and to diagnose
dynamical processes from the manner of the balance;
- to provide a high resolution sampling of the energetic eddy scales
in all four dimensions, i.e. 50 km horizontally, 500 m vertically and
15 days temporally;
- to obtain a statistical description for the low-frequency, hence
plausibly geostrophic, variability on finer scales, both in flow
variables and passive tracers;
- to take measurements near the ocean surface to allow a description
of mesocale variability in the surface layer during a time of general
warming and formation of the seasonal thermocline; and
- to make a further contribution to mapping the means, variances and
covariances of currents, density and other observables in the North
Atlantic subtropical gyre.
- 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
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).
- Abbreviation for
Particle and Optics Profiling System.
- Acronym for Physical Oceanography Research of the East Sea, a
subproject of the MECBES program of
- The tidal boretidalbore of the Amazon River.
- Acronym for
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
- 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,
the planetary vorticity, and
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.
To confuse the issue, a general form with wide applicability is
Ertel's potential vorticity. It follows from his potential vorticity
theorem and, according to Muller (1995), plays the most fundamental
role of all potential vorticity theorems because:
- it is most general, i.e. other vorticity and circulation theorems
can be derived from Ertel's theorem;
- potential vorticity becomes conserved in a variety of circumstances, thus
making the theorem a conservation law; and
- Ertel's potential vorticity equation is the governing equation for
an important class of motion where the equation becomes the sole prognostic
equation determining the time evolution of the flow, with all other
variables expressed in terms of the potential vorticity by diagnostic
The most general form of Ertel's theorem for a materially
conserved property is
where is the material derivative,
is Ertel's potential vorticity,
is the specific volume,
is the pressure, and the Jacobian given by
The corresponding potential vorticity is
is the relative vorticity,
is the constant angular velocity of the rotating frame, i.e. the
Earth's rotation rate,
Ertel's theorem in the
Boussinesq approximation is
is a constant reference density,
is the deviation of the density from a reference state, and
is a reference pressure.
The corresponding potential vorticity is
where the constant density can be dropped.
In the f plane approximation,
where spherical effects are neglected, the expression for the
potential vorticity is:
Bryan (1987) and
- Of any fluid whose density is function only of pressure and
potential temperature, i.e.
where is the pressure and the potential temperature.
- 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.
- 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 (PSS-78)
- 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
The practical salinity is defined in terms of the ratio
of the electrical conductivity of a seawater sample at
atmospheric pressure at 15C to that of KCl solution
containing 32.4356 g of KCl in a mass of 1 kg of solution at the
same pressure and temperature. This ratio defines
practical salinity of a sample according to
where = 0.0080, = -0.1692, = 25.3851,
= 14.0941, = -7.0261, and = 2.7081. This
definition suffices for laboratory determination of salinity
for samples at the aforementioned pressure and temperature,
but corrections must be made for in-situ measurements in
water of salinity and temperature . These are available
in the form of additional tables and equations.
This equation is valid for a practical salinity from 2 to 42.
The history and development of PSS-78 is summarized in
In 1964, a panel of scientists were appointed jointly by UNESCO, ICES,
SCOR and IAPSO to advise on the establishment of international tables
and standards. The first task of this Joint Panel of Oceanographic
Tables and Standards (JPOTS) was the preparation of tables for
computing salinity of seawater from determinations of electrical
conductivity. Before these tables could be prepared, it was necessary
to redefine salinity in terms of conductivity. After discussions
(UNESCO, 1965), the JPOTS recommended (UNESCO, 1966a) a definition
of salinity based on determinations of chlorinity and conductivity on
samples of natural seawater from all the oceans of the world.
In October 1966, the ``International Oceanographic Tables'' (UNESCO, 1966b)
for computing salinity from conductivity, based on the above
definition, were published. They included a tabulation of this
definition at 15C for salinities from 29 to 42 ppt, along with
a correction table for measurements at temperatures other than
15C, from 10 to 31C.
However, the use of in situ measurements of conductivity for
estimating salinity increased rapidly in the early seventies, rendering
the ``International Oceanographic Tables'' unsuited for use in the
majority of in situ measurements because the tables do not go
below 10C. Furthermore, a comparison to the conductivities
of seven batches of standard seawater, relative to a KCl solution
revealed that the conductivity of some batches was higher than than
calculated from the certified chlorinity (UNESCO, 1976). This raised
the problem of the calibration of the conductivity salinometers and
CTD probes, as well as the definition of salinity itself.
After discussion, the principle of calibrating standard seawater
in electrical conductivity with a potassium chloride solution, was
adopted and the establishment of a practical salinity scale was
recommended by the JPOTS (UNESCO, 1978). Intensive work was then
carried out in differnet laboratories with radically different measuring
equipment. This resulted in considerable data on which are based
the Practical Salinity Scale 1978, as well as the recommended algorithms
for the calculation of practical salinity from the conductivity ratio
at all temperatures and pressures over the range of oceanographic
interest (UNESCO, 1979). This was finally adopted by the JPOTS
during its meeting in Sidney, B.C., Canada, 1-5 September 1980
Whereas the previous salinity scale (UNESCO, 1966b) was based on a
conductivity-chlorinity relation using natural seawater, the Practical
Salinity Scale 1978 is different in that the standard seawater used
was diluted by weight with distilled water or evaporated to obtain
other salinity values. This procedure was followed to ensure the constancy
of composition of this seawater over the salinity range of interest.
A precisely specified solution of potassium chloride was chosen as
a reproducible electrical conductivity standard; an evaluation was then
made of the concentration of this solution which yields a conductivity
ratio of unity at 15C with respect to a standard
seawater (from the North Atlantic Ocean) whose certified chlorinity
was 19.3740 ppt, i.e. its salinity was exactly 35 ppt on the previous
salinity scale. By convention, its practical salinity, on the new
Practical Salinity Scale 1978, is 35, to ensure continuity at that
salinity with the previous scale.
Poisson and Gadhoumi (1993) extended PSS-78, which was
was limited to
salinities between 2-42, up to 50.
A polynomial was developed from laboratory measurements via
least-square regression fitting. The equation is:
where is the measured conductivity ratio, the measured
temperature, and the coefficients are:
The coefficients were calculated with eight decimal digits and rounded
off to obtain a salinity value that is different from the salinity calculated
by the eight decimal digital coefficient by
The standard deviation of the difference between the experimentally
measured salinities and those calculated using this equation is
. This equation is valid for the temperature
range 10-30C and the salinity range 35-50.
See Lewis (1980),
Lewis and Perkin (1981)
Poisson and Gadhoumi (1993) and
| = 77.37 10
|| = 39.89 10
| = -98.190 10
|| = -26.25 10
| = 34.73 10
|| = 48.205 10
| = 86.635 10
|| = -66.82 10
| = -10.018 10
|| = -46.56 10
- 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 is the Peclet number, the Reynolds number,
the kinematic viscosity, and
the thermal diffusivity.
When = 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 0C and 7 at 20C for water.
See Kraus and Businger (1994), p. 33.
- 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.
- 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).
- 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).
- primary productivity/production
- The amount of organic material produced by organisms from
inorganic material or, more technically, the amount of carbon fixed
by autotrophic organisms through the
synthesis of organic matter from inorganic compounds such as
carbon dioxide and water using energy derived from solar radiation or
This should be compared with:
Most of the primary production in the
oceans is due to
in the upper 100 m, i.e. the
Primary production is expressed in units of gC m yr where
gC is grams of carbon.
The total ocean productivity ranges from 75-150 gC m yr,
with photosynthesis accounting for around 95% of this and chemosynthesis
See Fogg (1975) and
- An experiment taking place during the summer of 1996 and the winter/early
spring of 1997 that focused on the shelfbreak front just south of
Cape Code on Nantucket Shoals.
See Pickart et al. (1999).
- 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).
- Princess Elizabeth Trough
- A gap in the topography between the Kerguelan Plateau and
the Antarctic continent, with a sill depth of 3750 m.
It provides a route for the exchange of
Antarctic Bottom Water (AABW) between the
Australian-Antarctic Basin and the Weddell-Enderby Basin.
See Heywood et al. (1999).
- 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.
- 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.
- Project FAMOUS
- The French American Mid-Ocean Undersea Study began in 1971 as part of
It was based on the general acceptance of the plate tectonic theory and
investigated the possibility of underwater hot springs.
The site selected was along the Mid-Atlantic Ridge near the Azores, and
was selected after detection of particularly strong magnetic stripes
in that region.
During FAMOUS over 100,000 photographs were taken and nearly 1,300 kg
of geological samples were collected by
Alvin and two French submersibles.
Water samples were also collected and a data logger was developed
to automatically record depth, altitude, heading and time.
- Acronym for Pre-Operational Modeling in the 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.
- 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).
- Joseph Proudman (1888-1975)
- See Cartwright and Ursell (1976).
- Proudman-Taylor theorem
- See Taylor-Proudman theorem.
- Acronym for PROcesses of Vertical Exchange in Shelf Seas, a joint European
funded project for an interdisciplinary study of the vertical fluxes of
through the water
column and the surface and bottom boundaries based on the
integrated application of new measuring techniques, new advances in
turbulence theory, and new models.
- 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.
- Prydz Bay
- The third largest embayment in the Antarctic continent.
Prydz Bay lies in the Indian Ocean sector, with typical depths of
A deep basin in the inner part of the bay descends to 800 m in
places, and to 1085 m adjacent to the Amery Ice Shelf.
Moving offshore from within the Bay, the bed rises from approximately
800 m to a sill at 400-500 m along 67-68S, and then falls
to 699 m at the edge of the continental slope some 100 km seaward.
The sill has a saddle point with 500 m depth at about
67S, 7130'E, where the bathymetry rises zonally
and falls meridionally.
Relatively shallow banks (Frame Bank to the west and Four Ladies
Bank to the east) rise to 200 m depth and extend over much of the shelf
width to either side of Prydz Bay, so deep connections between the ocean
and the Bay are concentrated through a broad region at the central
longitude of about 73E. A much narrow deep connection to the
shelf waters of the West Ice Shelf region east of the Bay is found
along a trough in the inner part of the shelf north of Davis station.
The waters of the southwestern part of the Bay come into direct contact
with a large floating ice shelf, the Amery Ice Shelf.
The large-scale circulation is dominated by a large cyclonic gyre
centered on the mid- to western part and extending from within the Bay to the
Antarctic Divergence northwest of
the Bay (at about 65S).
The gyre is associated with a relatively narrow coastal current running
from the southern limits of the Bay past the Amery Ice Shelf, and
continuing westward after leaving the Bay along the MacRobertson
Land Shelf (with velocities reaching 1 m/s in the latter part).
Part of the current flows offshore near 63E, while another
unknown fraction continues westward.
See Nunes Vaz (1996).
- Prydz Bay Bottom Water (PBBW)
- A type of regionally modified
Circumpolar Deep Water (CDW) which, along
with several other types of regionally modified and previously
defined types of CDW,
is now usually defined as one of several regional types of a more general
water mass called
Modified Circumpolar Deep Water.
See Middleton and Humphries (1989) and
Whitworth et al. (1998).
- See Andrews and McIntyre (1978).
- See Andrews and McIntyre (1978).
- 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).
- A WOCE hydrographic program in the North Pacific.
- 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 Practical Salinity Scale.
- 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.
- 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 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.