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FACTS

Acronym for Florida Atlantic Coast Transport Study. See Rinkel (1986).

Falkland Current

See Malvinas Current.

falling tide

That interval of the tidal cycle between a high water and the following low water. This is also known as ebb tide.

FAMOUS

Acronym for French-American Mid-Ocean Undersea Study. See Heirtzler and Van Andel (1977).

far infragravity waves

Waves in the nearshore zone at periods ranging from 100 to 1000 seconds. These were first discovered in 1986 as substantial energy in the velocity field in that period range, although no accompanying sea surface elevation signal was found, and their celerities were about an order of magnitude too slow to be consistent with a gravity wave explanation. They were eventually identified as shear waves arising from an instability of the strong mean longshore current. The dynamics are analogous to large scale flows, but with the role of the Coriolis force played by the shear of the longshore current. See Bowen and Holman (1989) and Holman (1995).

Faroe Shetland Channel

See Turrell et al. (1999).

FASINEX

Acronym for Frontal Air-Sea INteraction EXperiment, conducted from 1984 to 1986 in the subtropical convergence zone southwest of Bermuda. The overall objective was to study air-sea interaction on 1- to 100-km horizontal scales in a region of the open ocean characterized by strong horizontal gradients in upper ocean and sea surface properties. Among the specific questions addressed by this investigation were how lower atmospheric fluxes vary horizontally on scales determined by scales of oceanic variability, how strong horizontal sea surface temperature gradients associated with fronts affect the structure of the marine atmospheric boundary layer, what the magnitudes of changes in surface roughness, stress, and drag coefficients associated with cross-frontal gradients in SST are, and others. See Weller (1991) and Geernaert (1990).

[http://uop.whoi.edu/data/fasinex/fasinex.html]

FAST

1. Acronym for flow actuated sediment trap. 2. Acronym for fore-aft scanning technique.

FASTEX

Acronym for Fronts and Atlantic Storm Experiment, an experiment scheduled to take place from Feb.-Mar. 1997 whose aim is to advance the understanding and prediction of wintertime, oceanic, extra-tropical weather systems. It is designed to improve the forecasting of North Atlantic storms. See the FASTEX Web site.

feedback

Most generally this is a phenomenon where the output of a system is fed or cycled back into the input of the system, thus changing the output, etc. This is equivalent to saying that a system is nonlinear.

feeder current

See rip feeder current.

Ferrel, William (1817-1891)

See Peterson et al. (1996).

Ferrel cell

A mid-latitude mean atmospheric circulation cell for weather proposed by Ferrel in the 19th century. In this cell the air flows poleward and eastward near the surface and equatorward and westward at higher levels. This is now known to disagree with reality, although it is sometimes used to describe a mid-latitude circulation identifiable in mean meridional wind patterns.

fetch

In surface gravity wave generation theories, the length of water over which a wind is blowing. The wave height is completely determined in such theories by the fetch, the duration over which the wind blows, and the velocity of the wind. See Kinsman (1984).

FETCH

Acronym for Flux, Etat de la mer et Télédétection en condition de fetCH variable experiment in the Mediterranean Sea, which took place in March and April 1998. The objective was to measure and parameterize the turbulent fluxes at the ocean/atmosphere interface. See Hauser et al. (2000).

FGGE

Acronym for First Global GARP Experiment, which took place in 1970 and whose research objectives were to obtain a better understanding of atmospheric motion for the development of more realistic models for weather prediction and to assess the ultimate limit of predictability of weather systems. See Peixoto and Oort (1992) and the FGGE Web site.

FIBEX

Acronym for First International BIOMASS Experiment.

Fick's law

A law stating that the mass of a solute crossing a unit area per unit time in a given direction is proportional to the gradient of solute concentration in that direction. For a 1-D process it can be stated as

$$q\,=\,-D{{\partial C}\over{\partial x}}$$

where $q$ is the solute mass flux, $D$ the coefficient of proportionality, $C$ the mass concentration of diffusing solute, and $x$ the direction coordinate. The negative sign indicates that transport is from high to low concentrations. $D$ is called the diffusion coefficient or the molecular diffusivity. This was named for Adolf Fick, a German physiologist who published a paper in 1855 entitled ``Uber Diffusion'' in which he described the molecular diffusion process and derived his law. See Fischer et al. (1979).

FIDO

Acronym for Fluxes in the Deep Ocean instrument.

filter

In data or signal analysis, a function that selectively discriminates against some of the information passing through it. The discrimination is usually performed on the basis of frequency.

filtered equations

Equations derived by modifying the equations of motion in various ways. They are called filtered because the modifications filter out or remove certain dynamical processes or solutions that are deemed irrelevant to the phenomena being studied. Some oceanic examples are the spherical, shallow water, beta plane and the f plane approximations.

filtering approximation

See filtered equations.

Findlater jet

The atmospheric equivalent of an oceanic western boundary current. An example originates with the southwest monsoon that, fed partly from a northward extension of the easterly trade winds over the southern Indian ocean, develops in May. It turns northward and crosses the Equator in the vicinity of the African coast, confined by the highlands of Kenya and Ethiopia. This causes the winds to assume the familiar jet-like structure seen in western boundary currents in the oceans. See Findlater (1974) and Kraus and Businger (1994).

Findlay, Alexander George (1812-1875)

See Peterson et al. (1996).

Fine Resolution Antarctic Model

FRAM is a primitive equation numerical of the Southern Ocean between latitudes 24S and 79S based on the Cox/Bryan model. See Group (1991) and the FRAM Web site.

fingerprint method

A statistical technique developed to permit early detection of possible greenhouse warming. This method requires finding a multivariate signal (i.e. changes in a number of different climate parameters or changes in the same parameter at a number of different locations) unique to enhanced greenhouse effect model simulations and its accompanying identification in the observed climate record. Thus the method simultaneously satisfies two essential requirements, that the signal be both strong and unique. See Wigley and Barnett (1990).

finite element method

A numerical approximation method in which data is represented over some domain by a discrete series of functions. The domain is divided into a finite number of subregions called elements, whence the name. A series of functions is built up by defining a simple function, e.g. a low-order polynomial, on each element and requiring continuity between functions on adjacent subregions. The points where values are used to define the functions are conventionally called nodes and the defining parameters nodal values.

Finite elements are distinguished from spectral methods in that their approximations are local and not global, and they are distinguished from finite differences because the function is defined over a whole region rather than just a discrete points. Their use is more prevalent in modeling solid structures such as buildings or airplanes than it is for geophysical fluid flow, although several authors have constructed circulation models using finite elements. Perhaps their greatest advantage is the relative ease with which highly irregular boundaries can be handled as opposed to with the aforementioned spectral and finite difference methods.

fission-track dating

A radioisotopic dating method that depends on the tendency of uranium to undergo spontaneous fission as well as the usual decay process. The large amount of energy released in the fission process ejects the two nuclear fragments into the surrounding material, causing damage paths called fission tracks. These number of these tracks, generally 10-20$\mu$ in length, is a function of the initial uranium content of the sample and of time. The usefulness of this as a dating technique stems from the tendency of some materials to lose their fission-track records when heated, thus producing samples that contain fission-tracks produced since they last cooled down. The useful age range of this technique ranges from 100 to 100 million years BP, although error estimates are difficult to assess and rarely given.

A problem with fission-track dating is that the rates of spontaneous fission are very slow, requiring the presence of a significant amount of uranium in a sample to produce useful numbers of tracks over time. Additionally, variations in uranium content within a sample can lead to large variations in fission track counts in different sample sections. This method is used more often in archaeology than in paleoclimatology, with other dating methods, e.g. argon-argon dating, preferable for the purposes of the latter field, although it can provide useful results in the 30,000 to 100,000 years BP window that strains the upper and lower limits of the other widely used dating methods. See Bradley (1985).

fjord

More later.

fjord entrainment estuary

One of the four principal types of estuaries as distinguished by prevailing flow conditions. This type features a relatively stagnant, deep water mass overlain by a thin river runoff flow, e.g. prevailing summer conditions for the Norwegian fjords.

Fjortoft's theorem

A theorem that is a consequence of both vorticity and enstrophy being conserved in the two-dimensional flow an inviscid homogeneous fluid. It states that the transfer of energy from one scale to a smaller (larger) scale must be accompanied by the simultaneous transfer to a larger (smaller) scale. This result of 2-D turbulence contrast strongly with those from 3-D turbulence where 3-D stretching and twisting terms allow other avenues for energy transfer. This is also known as the anti-cascade theorem. See Hide (1978).

FLAME

Acronym for Family of Linked Atlantic Model Experiments, a framework for several numerical ocean modeling projects that study the physics and biogeochemistry of the Atlantic Ocean. The goal of FLAME is to perform a series of sensitivity studies with respect to key parameters of the ocean's dynamics.

[http://www.ifm.uni-kiel.de/to/FLAME/]

FLEX

Acronym for Fladen Ground Experiment, a part of JONSDAP 76.

[http://www.gotm.net/html/0-CASES/FLEX.html]

FLIP

Acronym for Floating Instrument Platform. See the FLIP Web site.

Flores Sea

See Gordon et al. (1994).

Florida Bay

See Wang (1998).

Florida Current

See Schmitz and Richardson (1991).

fluorescence

The re-emission of light energy at a lower frequency by an absorber illuminated with optical energy. The response is usually immediate and on order 1 to 3% of the incident intensity.

fluorometer

A device used to measure the concentration of chlorophyll in sea water. It does this by mimicking the sun and emitting a flash of light at a specific wavelength and causing the phytoplankton present to fluoresce at another wavelength. The light emitted by the plankton is measured and converted to a chlorophyll measurement via a calibration obtained from discrete measurements of known quantities of chlorophyll. An a-c meter is also used to measure chlorophyll.

flux adjustment

See flux correction.

flux correction

An ad hoc procedure by which the values of dependent variables at the air-sea interface in coupled atmosphere-ocean model runs are adjusted to better conform to observed values. For example, heat flux is corrected by first running the ocean model and calculating the heat flux needed to correct the differences between the observed and calculated surface temperatures. Next the atmospheric model is run with observed values of SST and the net heat flux from the atmosphere is calculated. The coupled model is then run with the difference between these ocean and atmospheric heat fluxes added to those calculated by the coupled model at each time step. A similar procedure can be followed with other variables. These methods are designed to remove most of the tendency of coupled models to drift towards their own climate replete with systematic errors. The most difficult area to apply this procedure is over ice. It is expected that this will become much less of an issue as the model components are improved. See Sausen et al. (1988) and Meehl (1992).

flux Richardson number

A dimensionless number expressing the ratio of turbulent energy lost to buoyant forces to the energy gained by eddy stress acting on the mean shear. It is the crucial nondimensional number for turbulence in stratified, shearing flow and can be expressed in a couple of different ways by

$$Rf\,=\,{{K_H}\over{K_M}}Ri\,=\,{{K_M}\over{k{u_*}L}}$$

where $K_H$ and $K_M$ are eddy viscosity or vertical transport coefficients for heat and momentum, respectively, $Ri$ the gradient Richardson number, $u_*$ the friction velocity, $k$ is von Karman's constant, and $L$ a length scale. The definition of this is different than that for the overall and gradient Richardson numbers. See Turner (1973) and Dutton (1986).