Bn-Bz

 

BODC

Abbreviation for the British Oceanographic Data Center. See the BODC Web site.

 

BOFS

Abbreviation for Biogeochemical Ocean Flux Study, a U.K. contribution to JGOFS funded by the NERC. The goal of GOFS was to study differences in glacial-interglacial paleoenvironments of the eastern Atlantic Ocean, especially between the last glacial and the Holocene. The results are presented in a special issue of Paleoceanography (Vol. 10, No. 3, 1995). See especially the short review by Elderfield and Thomas (1995).

 

Bohai Gulf

More later.

 

Bohnecke mechanical recording current meter

A mechanical current meter, first designed and used in the 1930s, in which the propellor and the compass both drive a set of horizontal dials with raised numbers on their vertical rims. A clockwork mechanism moves a strip of tin foil past the vertical rims of the dials and a hammer presses the the foil against the raised numbers on the rims every 5 or 10 minutes. The speed and direction can be obtained from the information on the foil. Wide use of this mechanism was forestalled by the difficulty in finding a material for the spring in the clockwork that could withstand the corrosive exposure to sea water. See Sverdrup et al. (1942).

 

bolide

A very bright meteor; one that usually explodes.

 

Bolling oscillation

A post-LGM European climate regime. This refers to around 12,000 BC when temperatures were rising rapidly. Tundra persisted in unfavorable sites but elsewhere vegetation types of more temperate climes advanced. It was preceded by the Oldest Dryas and followed by the Allerod oscillation. See Lamb (1985), p. 371.

 

Boltzman equation

The Navier-Stokes equations can be derived from the Boltzmann equation by considering appropriate limits, i.e. Knudsen and Mach numbers tending to zero, and appropriate averaging procedures to define new coarse-grained variables (velocity and pressure) and associated transport coefficients (viscosity and density). See Farge et al. (1996).

 

bolus velocity

See eddy-induced transport velocity.

 

BOMEX

Acronym for Barbados Oceanography Meteorology EXperiment.

 

BOP

Abbreviation for Bayesian oscillation patterns, patterns found using BSA. See Ruiz de Elvira and Bevia (1994).

 

BOPS

Acronym for Bio-Optical Profiling System, an instrument for measuring optical and physical parameters in the water column.

 

bora

A cold, often very dry, northeasterly wind which blows, sometimes in violent gusts, down from the mountains on the eastern shore of the Adriatic Sea. It is strongest and most frequent in winter and on the northern part of the shore, and occurs when pressure is high over central Europe and the Balkans and low over the Mediterranean. This term is also generally applied to cold, squally, downslope winds in other parts of the world.

 

boreal forest

A plant formation type associated with cold-temperate climates (cool summers and long winters). This is also known as either taiga or coniferous evergreen forest. The dominant plants are spruces, firs, larches and pines.

 

Boreal period

A post-LGM European climate regime. This refers to the period from about 7000-6000 BC when temperatures continued to rise, e.g. the colder seasons of the year gradually became milder (although probably with some dry and frosty winters) and the summers became generally warmer than today. It was preceded by the Pre-Boreal period and followed by the Atlantic period. See Lamb (1985), p. 372.

 

BOREAS

Acronym for the Boreal Forest Ecosystem-Atmosphere Study, a global change project to study and understand the interaction between the boreal forest biome and the atmosphere. See the BOREAS Web site and Group (1993).

 

borehole temperatures

A record of past changes of temperature at the Earth's surface that have penetrated into the subsurface and have been recorded as transient perturbations to the steady state temperature field. This can provide information about climate change over the past few centuries. Low frequency surface temperature variations occurring in the past 300 years can be detected in a borehole over 600 meters deep. Thousands of borehole records are available for such an analysis, although the interpretation of the records can be occasionally tricky. For instance, local changes around the borehole, e.g. changes in snow cover, tree growth, etc., must sometimes be filtered out. See Karl et al. (1995).

 

Bothnian Sea

See Gulf of Bothnia.

 

boundary stratotype

A rock section containing the time line or boundary that marks the standard demarcation between chronostratigraphic units. The time line is, in practice, usually based on biostratigraphic evidence such as the appearance or disappearance of a key species or other taxon.

 

Boussinesq approximation

Actually a set of filtering approximations (attributed to Boussinesq) that results in an equation set applied to almost all oceanic motions except sound waves. The four approximation steps are: (1) subtracting a motionless hydrostatically balanced reference state from the equations of motion; (2) making the anelastic approximation; (3) assuming that the vertical scale of motion is small compared to the scale depth (or height); and (4) ignoring the inertial but not the buoyancy effects of variations in the mean density. The name ``Boussinesq approximation'' is not always used identically with the above series of approximation steps and may or may not include the assumption of incompressibility. See Spiegel and Veronis (1960), Phillips (1977), pp. 15-20, Zeytounian (1990), pp. 142-176, and Muller (1995).

 

Boussole Strait

See Okhotsk Sea.

 

Bowen ratio

The ratio of the amount of sensible to that of latent heat lost by a surface to the atmosphere by the processes of conduction and turbulence.

 

Brandenburger Biosphere Model

For more information see the BBM Web site.

 

Braun-Blanquet school

One of two major schools of thought in phytosociology in the first half of the twentieth century, the other being the Clementsian school. This school, based in Europe and also known as Zuricho-Montpellier, had at its core the concept of the plant association as the basic vegetational unit. The characteristic species were deemed to give a more positive indication of ecological conditions than the dominants, although the latter could also be characteristic species. This school uses an inductive methodology. See McIntosh (1978).

 

brave west winds

See roaring forties.

 

Brazil Current

More later.

 

Brewer-Dobson circulation

The meridional atmospheric circulation that transports air poleward and downward from the tropical middle atmosphere. Air is transferred between the equator and poles by this circulation on a time scale of months, indicative of the strong control by the Coriolis force that deflects the air stream zonally and inhibits meridional motions. See Salby (1992).

 

brickfielder

A hot wind of southeastern Australia caused by the movement of tropical air southwards. This occurs especially during the summer and often brings clouds of dust. It brings hot spells of many days duration where temperatures can exceed 100 deg. F. It is similiar to the South American zonda.

 

broad-leaved evergreen forest

A plant formation type associated with warm temperate climates. The trees in this type tend to be sensitive to frost.

 

Bruckner cycle

A hypothesized recurrence in northwestern Europe of periods of cold and damp alternating with warm and dry years, the average interval between successive maxima being 34.8 years (as calculated by E. Bruckner in 1890), though individual cycles vary from 25 to 50 years.

 

Brunhes Magnetic Epoch

Normal magnetic polarity time interval extending from the present back to 600,000 years ago.

 

Brunt frequency

See buoyancy frequency.

 

Brunt-Vaisala frequency

See buoyancy frequency.

 

BSA

Abbreviation for Bayesian signal analysis, a method designed to be optimal for analyzing short time series which can work with an SNR as low as 0.6. No hypotheses are made about the actual series belonging to any hypothetical ensemble or infinite series; only the given data are used to find the probability of some a priori signal being contained in the data. A measure of the accuracy of the estimate can also be obtained. See Ruiz de Elvira and Bevia (1994).

 

BSRN

Abbreviation for Baseline Surface Radiation Network, a network of over 25 stations located throughout the world to provide data for the calibration of the SRB Project and other satellite-based measurements of radiative fluxes as well as for the validation of radiative flux models. The data from this GEWEX project are archived at the WRMC and also at the NASA EOS DAAC. See the BSRN Web site.

 

Buchanan, John Young

More later.

 

bucket model

A soil water budget model in which the surface is represented by a field of buckets of specified depth.

 

bucket temperature

The surface temperature of the ocean as measured by a bucket thermometer. This can also be the temperature measured by immersing a surface thermometer into a freshly drawn bucket of water.

 

bucket thermometer

A thermometer with an insulated container around the bulb. It is used to measure ocean temperatures by lowering it on a line, allowing it to equilibrate with the temperature of the surface water, withdrawing it along with the water surrounding it, and reading the temperature. The water serves both as insulation for the thermometer (after withdrawal) and as a sample for a salinity determination.

 

buffer factor

Defined as the fractional change in atmospheric CO2 divided by the fractional change in oceanic DIC after equilibrium has been reached. This factor characterizes the fraction of the CO2 flux from the atmosphere to the mixed layer that will react to form carbonate and bicarbonate ions. This is also known as the Revelle factor. See Najjar (1991).

 

buffer sublayer

That part of a boundary layer where the viscous stress and the Reynolds stress have the same order of magnitude and the linear velocity profile turns smoothly into the logarithmic profile. See Kagan (1995).

 

buoyancy frequency

The frequency with which a parcel or particle of fluid displaced a small vertical distance from its equilibrium position in a stable environment will oscillate. It will oscillate in simple harmonic motion with an angular frequency defined by

where g is the gravitational acceleration, a standard constant density, and the density. See Turner (1973).

 

buran

A strong northeasterly wind that occurs in Russia and central Asia. It is most frequent in winter, but such winds that occur in summer are also called buran. Such a wind bearing snow in winter is also called a purga.

 

Burdigalian

The second of six ages in the Miocene epoch (the second of two in the Early Miocene), lasting from 21.8 to 16.6 Ma. It is preceded by the Aquitanian age and followed by the Langhian age.

 

Burma Sea

See Andaman Sea.

 

Buys Ballot's law

A synoptic meteorology rule stating that if, in the northern hemisphere, an observer stands with his back to the wind, pressure is lower on his left hand than on his right, while in the southern hemisphere the converse is true. This was enunciated by Buys Ballot of Utrecht in 1857 and is basically a restatement of the fact that winds blow clockwise around a depression in the northern hemisphere and anticlockwise in the southern hemisphere.