Fa-Fm

 

faculae

Areas of increased brightness on the surface of the sun. Contrast to sunspots.

 

facultative chemotroph

A species of phytoplankton that possesses photosynthetic pigments but is able to grow either with or without light, as opposed to the obligate chemotrophs.

 

Faint Young Sun Paradox

Models of solar evolution indicate that the solar luminosity increased 20-30% over the past 4.7 Ga. As such, the amount of solar radiation received by the young Earth must have been significantly less than today, and the effective radiation temperature 10-15 K less than today. Also, climate models indicate that a reduction of 5-10% in the solar constant would result in an ice-covered Earth, with the resultant ice-albedo feedback maintaining that state even with solar constant values greater than at present. As such the apparent paradox involves how the Earth kept from freezing over and staying so permanently in light of the fact that it didn't. A couple of theories have been advanced toward resolving this paradox: (1) a higher percentage of CO2 in the atmosphere of the early Earth trapped more heat via the greenhouse effect and (2) the early Sun may have lost mass as it evolved, resulting in an early solar luminosity much higher than previously thought. At present an adequate resolution is not forthcoming.

 

Falkland Current

More later.

 

FANGIO

Acronym for the Feedback Analysis of GCMs for Intercomparison with Observations, a program for the intercomparison of various GCMs. See Cess et al. (1990) and Cess et al. (1991).

 

FASINEX

Acronym for Frontal Air-Sea INteraction EXperiment.

 

FAUNMAP

Abbreviation for FAUNal MAP, an electronic database documenting late Quaternary distributions of mammal species. See the FAUNMAP Web site.

 

FCCC

Abbreviation for the Framework Convention on Climate Change, an agreement among nations to study and act on the possibility of climate changes due to anthropogenic perturbations like increased greenhouse gases in the atmosphere. See the FCCC Web site.

 

FCL

Abbreviation for Fixed Cloud Level.

 

FED

Acronym for the Forest Ecosystem Dynamics project, whose goal is to use forest succession models, soil process models, and radiation scattering models models, combined with ground-based and remotely sensed observations, to improve understanding of the dynamics of northern/boreal forest ecosystems over a range of spatial and temporal scales. See the FED Web site for further information.

 

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.

 

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.

 

fertilization effect

See carbon dioxide fertilization.

 

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).

 

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.

 

FIAMS

Acronym for the Flinders Insitute for Atmospheric and Marine Sciences, located in Adelaid, South Australia. See the FIAMS Web site.

 

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

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),

 

field capacity

In modeling land surface processes, this is a parameter estimated as the water content of the soil a few days following a saturating rain when the water drainage rate has become less than some small value. Whatever the precise definition of this admittedly fuzzy concept may be, it is generally much less than the saturated water content of the soil. The field capacity is used, when subtracted from the soil water content at the wilting point, to ascertain the amount of water than can be stored in a soil. See Dickinson (1992).

 

FIFE

Acronym for First ISLSCP Field Experiment, a local-scale climatology project set in the prairies of central Kansas during 1987-1989 designed to study the flows of heat and moisture between the land surface and the atmosphere over a region 15x15 km in size. This was achieved by coordinating satellite overpasses with aircraft and ground data collection over the same area at the same time. The monitoring data are continous through the three years while intensive field work was conducted in 1987 and 1989. See See Sellers et al. (1992) and the FIFE Web site.

 

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.

 

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.

 

Finlater 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 Kraus and Businger (1994).

 

FIRE

Acronym for First ISCCP Regional Experiment, a multidisciplinary program to study the roles that clouds play in the global climate. Components of the program include both physical process modeling on many different space and time scales and global climate modeling. The general study objectives are the characterization of clouds, the validation and improvement of satellite cloud retrieval techniques, the improvement of cloud radiation models, the description of cloud space/time statistics, the improvement of cloud dynamics models, and the validation and improvement of GCM cloud model parameterizations. See Cox et al. (1987) and the FIRE Web site.

 

firn

A transitional stage between snow crystals and ice where the increasing weight of the overlying material causes the snow crystals to settle, deform and recrystallize, leading to an increase in unit density. Further increases in the overburden causes the firn to continue to increase in density as the air spaces in the crystals are reduced by mechanical packing and plastic deformation. The interconnected air passages are sealed off into individual air bubbles at a density of about 0.83 kg/m3, marking the transition into ice.

 

First Point of Aries

The point in which the ecliptic intersects the celestial equator, crossing it from south to north. This is the origin from which both right ascension and celestial longitude are measured.

 

FIS

Abbreviation for FIFE Information System, a data system to serve as a tool for designing the experiment as well as for organizing and manipulating the complex data set before and after the data collection effort. See Strebel et al. (1990).

 

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).

 

Flandrian Transgression

See King (1962).

 

flora

The sum total of all the plant species in an area, as opposed to the vegetation. This can also apply to assemblages of fossil plants from a particular geological time or region within that time. Examples include British flora or Carboniferous flora.

 

Flores Sea

More later.

 

Florida Current

More later.

 

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.

 

flux adjustment

See flux correction.

 

flux aggregation

A type of averaging used in SVAT models wherein fluxes (rather than the parameters used to calculate the fluxes) due to various soil and vegetation types in a grid box are averaged to obtain an overall value for the grid box. This is used when parameter aggregation is insufficient, and is necessary due to the spatial inhomogeneity of the land surface characteristics within individual grid boxes. See Houghton and Filho (1995).

 

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 coupler

In numerical modeling, this is a software mechanism whereby in coupled atmosphere/ocean circulation models state variables (e.g. temperature, salinity, etc.) are passed out of component models to a coupler which only computes fluxes and returns these to the component models. This is one way to speed up numerical integrations using the methods of parallel computing.

 

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

where and are eddy viscosity or vertical transport coefficients for heat and momentum, respectively, Ri the gradient Richardson number, 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).