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).

 

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.

 

POC

Abbreviation for particulate organic carbon.

 

PODS

Acronym for Pilot Ocean Data System.

 

POEM

Acronym for Physical Oceanography of the Eastern Mediterranean.

 

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 deg. 28 min. 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 Front

In physical oceanography, a region of rapid transition in the Southern Ocean between the Polar Frontal Zone and the Antarctic Zone. It is identified by a crowding of isotherms at the surface around 5-6 deg. C.

 

Polar Frontal Zone

In physical oceanography, the name given to a transition region in the Southern Ocean between the Subantarctic Zone and the Antarctic Zone. It is bounded by the Subantarctic Front to the north and the Polar Front to the south. It is pragmatically identified as the region bound by the 3-9 deg. C surface isotherms.

 

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).

 

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 Polarizatino and Directionary of the Earth's Reflectances, an instrument that observes the polarization, directional and spectral characteristics of the solar light reflected by aerosols, clouds, oceans and land surfaces. POLDER is a push broom, wide field-of-view, multi-band imaging radiometer/polarimeter. It will fly on the ADEOS mission.

 

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.

 

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 open water area within sea ice.

 

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).

 

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.

 

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 dating method based on the decay of the radio-isotope K40 (potassium) to a daughter isotope Ar40 (argon). The rocks of volcanic origin that are dated using this method are assumed to have been initially free from argon since it is removed by heating, and thus the ratio of the K40 to any Ar40 decay product driven off the sample in the laboratory is a function of the age of the sample. This method is used mostly for samples formed in the last 30 million years but is limited to samples greater than 100,000 years old due to the half-life of K40. See Bradley (1985), Ch. 3.

 

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 atmospheric pressure.

 

potential surface

See geopotential surface.

 

potential temperature

A physical oceanographic term for the temperature that a water sample gathered at depth would 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.

 

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

The vorticity a column of air or water between two isentropic surfaces would have if it were brought by an adiabatic process to an arbitrary standard latitude and then stretched or shrunk to an arbitrary standard thickness. It is a conservative property for adiabatic processes which, given the vertical component of vorticity , the Coriolis parameter f, the thickness h, and the subscripts 0 and 1 for, respectively, before and after the standardization, can be expressed as:

. The conservation of this property is often expressed as a consequence of Ertel's theorem.

 

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 measures basically the same thing as the older ppt scale. See Tomczak and Godfrey (1994).

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.

 

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).

 

purga

See buran.

 

PUV

Abbreviation for Profiling Ultraviolet Instrument.

 

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.