Pn-Pz

 

PNA

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).

 

PNCERS

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. See the 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).

 

PNL

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.

 

PNTS

Abbreviation for Programme National de Télédétection Spatiale.

 

POAM

Acronym for Polar Ozone and Aerosol Measurements.

 

POC

Abbreviation for particulate organic carbon.

 

POCEX

Acronym for Pacific Ocean Color Experiment, See the POCEX Web site.

 

PODS

Acronym for Pilot Ocean Data System.

 

POEM

Acronym for Physical Oceanography of the Eastern Mediterranean. See Malanotte-Rizzoli and Robinson (1988) and Robinson et al. (1992).

 

POES

Abbreviation for Polar-orbiting Operational Environmental Satellites.

 

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 with the Rossby radius. 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 inertial waves. The dispersion relation for Poincare waves is where 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 binomial distribution 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 Antarctic Circumpolar 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 Southern Ocean between the Subantarctic Front and the Polar Front. It is 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 and the Antarctic Zone (AZ) and Continental Zone (CZ) to the south. 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 Atlantic Ocean. It is identified as a distinct temperature minimum layer underneath the 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.

 

POLDER

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 the IGBP. See the POLDER Web site.

 

POLES

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.

 

POLEX

Acronym for Polar Experiment, a FGGE project.

 

pollen-climate response surface

See climate space.

 

polychoria

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 relief differences. See McIntosh (1978).

 

POLYGON

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).

 

POLYMODE

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.

 

polynya

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 heat budgets. 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 feeding grounds.

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).

 

POM

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).

 

PONAM

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.

 

ponente

A westerly wind blowing in the Mediterranean area.

 

POP

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

More later.

 

pororoca

The tidal boretidalbore of the Amazon River.

 

PORTS

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 ice-albedo feedback mechanism.

 

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 argon-argon dating 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 somehow limited.

 

potential evapotranspiration

The theoretical maximum amount of water vapor that can be convyed to the atmosphere by the combined processes of evaporation and transpiration 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, potential temperature, 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 abbreviated.

 

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 as

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 latitude. See Stommel (1987).

 

potential vorticity

In the simplest case, this is a quantity equal to

in a 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).

 

power

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.

 

ppb

Abbreviation for parts per billion.

 

ppm

Abbreviation for parts per million.

 

PPP

1. Abbreviation for principal prediction patterns, used synonymously for EOF. 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 per thousand. 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.

 

PRARE

Acronym for Precise Range and Range Rate Experiment, which ran on ERS-1.

 

PRCM

Abbreviation for Paleoclimate Reconstruction for Climate Modeling.

 

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.

 

Precambrian

All of geologic time before the Phanerozoic eon, i.e. about 90  

precession

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.

 

precision

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 conditions. 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 external parameters. See Lorenz (1975) and Kagan (1995).

 

pre-displacement

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 absorption lines 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 troposphere.

 

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 motion.

 

Prestwich, Joseph (1812-1896)

See Peterson et al. (1996), p. 96.

 

prewhitening

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 is detrending. See Burroughs (1992).

 

Priabonian

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 Oligocene epoch.

 

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 photosynthesis of phytoplanktonic algae. in the upper 100 m, i.e. the euphotic zone. See Fogg (1975).

 

PRIME

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 hydrostatic approximation 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).

 

PRIRODA

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). See the PRIRODA Web site.

 

PRISM

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 Gaussian, binomial, Poisson, chi-square and Cauchy distributions. This is also known as a probability function.

 

PROBE

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.

 

PROBES

Acronym for Processes and Resources of the Bering Sea Shelf.

 

PROFILE

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.

 

prognostic

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.

 

PROMISE

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. See the PROMISE Web site.

 

Proterozoic

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.

 

PROTEUS

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).

 

Protozoa

An animal phylum of unicellular, eukaryotic micro-organisms, the most important groups of which for paleoclimatology are Foraminifera and radiolarians. 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.

 

PRR

Abbreviation for Profiling Reflectance Radiometer.

 

PSA

Abbreviation for Phycological Society of America.

 

PSC

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 odd nitrogen. See McCormick et al. (1993).

 

pseudomorph

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.

 

pseudopod

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).

 

PSMSL

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.

 

psychrometrics

The study of the physical and thermodynamic properties of the atmosphere. The properties mainly of concern are dry-bulb temperature, wet-bulb temperature, dew-point temperature, absolute humidity, relative (or percent) humidity, sensible heat, latent heat, 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 interrelationships.

 

psychrosphere

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 ocean stratosphere.

 

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 sea floor. See Tchernia (1980).

 

Purdy, John (1773-1843)

See Peterson et al. (1996), p. 59.

 

purga

See buran.

 

PUV

Abbreviation for Profiling Ultraviolet Instrument.

 

PW

Abbreviation for Polar Water.

 

pycnocline

In physical oceanography, a layer where density changes most rapidly with depth. It can be associated with either a thermocline or a halocline.

 

pycnostad

In physical oceanography, a layer where the vertical change of density is very small and displays a local minimum.

 

pyranometer

An instrument for measuring either the diffuse or the total global solar radiation.

 

pyrgeometer

An instrument for measuring the longwave atmospheric radiation or the outward radiation from the Earth's surface.

 

pyrheliometer

An instrument for measuring direct solar radiation, excluding the diffuse and reflected components.

 

Pyrrophyta

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 phagotrophically.