物理海洋学名词-V 447

Glossary of Physical Oceanography and Related Disciplines

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

May 26, 2004

 

VACM See Vector Averaging Current Meter.


Vaisala frequency See buoyancy frequency.


valley The official IHO definition for this undersea feature name is “a relatively shallow, wide depression, the bottom of which usually has a continuous gradient; this term is generally not used for features that have canyon–like characteristics for a significant portion of their extent; also called submarine valley or sea valley.”


vapor concentration See absolute humidity.


vapor pressure The vapor pressure of water vapor in moist air is given by
e'=pr/(0.62197 + r)
where p is the pressure and r the mixing ratio.


Varen, Bernhard (1622-1650?) A German physician who is commonly accredited with being the founder of modern general geography. He summarized, amongst many other things, the current state of knowledge about the sea in his book Geographia Generalis (later published in English as A Compleat System of General Geography), first published in 1650. The book was important for being the first comprehensive and objective collection of geographical knowledge since the Greek Classical Age and for its reflection of a growing appreciation and use of empirical knowledge to guide explanations rather than the reliance on fantasy and speculation that had prevailed for more than a millenia (although Varen did indeed lapse into the latter on more than a few occasions).
Varen’s most important contribution to oceanography was probably the discussions in his book about steady currents being driven by the wind, the first time this notion had seen print. This led to motions in the sea finally being considered in terms other than Aristotle’s primum mobile. He also attempted to categorize the motions of the sea, separating them into a continuous western flow, an observed periodic rise and fall of the sea surface that is the tide (although their connection with the moon was suspected though not as yet well-known), and various special flows including what are now known as the Florida, Kuroshio and Mozambique Currents.
Varen also discussed varying theories as to the causes of the perceived general westward flow and the tides. The explanations for the former included a magnetic pull from the moon, thermal expansion as a result of moonlight, downward pressure from the moon as trasmitted through an endless atmosphere, the sun pulling the water after it, the inability of the sea to keep up with the earth’s rotation, and more. He concluded that the cause was uncertain although he favored the wind as a cause at least of the general westward currents in the tropics as well as of other non-tidal currents flowing counter to the supposed general western flow. He considered the moon as responsible for the tides although via a mechanism as yet unknown (and to be identified by Newton in 1687). See Peterson et al. [1996].


variance ellipse


Vector Averaging Current Meter A current meter used in oceanography that senses speed with a Savonius rotor and direction relative to its case with a vane assembly. An internal compass senses the orientation of the case relative to magnetic north. Temperature is also recorded. The data recorded by the internal electronics is a true vector average with the sampling rate for speed and direction partly determined by the rotor rotation rate. See Heinmuller [1983].

 

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