物理海洋学名词-B 47

Glossary of Physical Oceanography and Related Disciplines

Steven K. Baum Department of Oceanography Texas A&M University

May 26, 2004

 

backing   Said of the anti-clockwise change of direction of a wind, as opposed to veering.

 

backscattering cross–section   The ratio of the acoustic power scattered at an angle of 180◦ from the incident acoustic wave to the acoustic intensity incident on a unit volume or area. This measure,typically referenced to a unit distance, e.g. 1 m, is the ratio of the reflected acoustic power to incident acoustic power per unit area. The units of this ratio are area, e.g. m2.

 

backshore   That part or zone of a beach profile that extends landward from the sloping foreshore to a point of either vegetation development or a change of physiography, e.g. a sea cliff or a dune field. See Komar [1976].

 

Baffin Bay   A large sea located between the Canadian Archipelago and the Labrador Sea. It is about 1000 km and 400 km. Most of Baffin Bay is deeper than 1500 m, but deep water exchange with the Labrador Sea is restricted by a sill in Davis Strait with a depth of 670 m. A mobile ice cover forms during winter and moves southward under the prevailing winds. Icebergs calved from glaicers in southern and western Greenland drift across the bay and southward in the Baffin Current to southern latitudes. A significant oceanographic feature of Baffin Bay is the North Water, a partially open water area in the northern part where complete ice cover would be expected under prevailing climatological conditions.

The principal currents are a relatively warm northwards flowing current along the Greenland coast,and the cold southwards flowing Baffin Current. This cyclonic circulation is driven by surface inflows of low salinity Arctic water through the Canadian Archipelago in the north and by means of the West Greenland Current in the south. Current meter data from northern Baffin Bay show strong surface Arctic outflows to a depth of about 500 m, directed to the south and generally following the bathymetry. There is a strong annual cycle in the mean currents, with the currents stronger in summer and weaker in winter. This variability is probably driven by seasonal changes in buoyancy forcing, which enhances the coastal currents on the wide shelves. Tidal currents up to 0.4 m s−1 have been observed on the shelves and along the shelf slopes, and consist mainly of semidiurnal components, with a considerable diurnal component in some areas. The surface layer, defined as the layer extending to the maximum depth influenced by wind stress, is a few tens of meters thick. The surface layer water has a density of 1026 kg/m3 or less, with the deeper water weighing in at 1027 kg/m3. Their salinities are 32.5 and 34.0,respectively. In the eastern part of the bay there is a layer between about 200 and 800 m characterized by relatively warm and salinewater. This is considered the result of inflow of Atlantic water through the Davis Strait. Substantial tidal currents have been measured in the eastern part of the bay, e.g. up to about 20 cm/s at locations where the water depth is 500 m. See Ingram and Prinsenberg [1998].

[http://www.bmp.gl/E/EB3 petroleum/EB3 50ba 10na baffin.html]

 

baguio  The local name given to tropical cyclones in the Phillipines,especially those occurring from July to November.

 

balanced equations   Approximations to the primitive equations that filter out the inertia–gravity wavesbut retain the geostrophic motions. Examples include:

• planetary geostrophic equations

• quasi–geostrophic equations

• semi–geostrophic equations

The primitive and planetary geostrophic equations can be seen as the limiting cases, with the former including all motions and the latter filtering a wide range of motions via its complete omission of inertia. The other equation sets are attempts to find a compromise between the former and latter. See McWilliams and Gent [1980], G. and Flierl [1981] (p. 508), Salmon [1985], Allen et al. [1990], Allen [1993], Allen and Newberger [1993], Muller [1995] and Mohebalhojeh and Dritschel [2001].  

 

QY@108,20170712

共收到 0 | 阅读次数 141
发表评论
请先登录再发表评论