Tides

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  • Tides
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  • Pertaining to the study of the periodic rise and fall of the sea surface, generated by long-wavelength waves which are caused by the interaction of gravitational force and inertia. Variables include characteristics of tides and other aspects important to their study.  
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Abstract from DBPedia
    Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. The times and amplitude of tides at a locale are influenced by the alignment of the Sun and Moon, by the pattern of tides in the deep ocean, by the amphidromic systems of the oceans, and the shape of the coastline and near-shore bathymetry (see Timing). Some shorelines experience a semi-diurnal tide - two nearly equal high and low tides each day. Other locations experience a diurnal tide - only one high and low tide each day. A "mixed tide"; two uneven tides a day, or one high and one low, is also possible. Tides vary on timescales ranging from hours to years due to a number of factors. To make accurate records, tide gauges at fixed stations measure the water level over time. Gauges ignore variations caused by waves with periods shorter than minutes. These data are compared to the reference (or datum) level usually called mean sea level. While tides are usually the largest source of short-term sea-level fluctuations, sea levels are also subject to forces such as wind and barometric pressure changes, resulting in storm surges, especially in shallow seas and near coasts. Tidal phenomena are not limited to the oceans, but can occur in other systems whenever a gravitational field that varies in time and space is present. For example, the solid part of the Earth is affected by tides, though this is not as easily seen as the water tidal movements.

    潮汐(ちょうせき、英語: tide)は、主に他の天体の潮汐力により、天体の表面などが上下する現象である。 地球の海面の潮汐である海洋潮汐・海面潮汐が広く知られているが、湖沼でも琵琶湖、霞ヶ浦程度の大きさがあれば起こる。また液体でなくても、大気(大気潮汐)や固体地球(地球潮汐)にも、また他の天体でも起こる。 しおともいう。漢字では潮と書くが、本来は「潮」は朝のしお、「汐」は夕方のしおの意味である。なお原義としてはこれだが一般には海に関するいろいろな意味で「潮」が(まれに「汐」も)使われる。 海(や大気)のように天体の表面が流体で蔽われている場合、潮汐にともない、表面が下がるところから上がるところへ流体が寄せ集められるために流体の流れ(水平動)が生まれる。これを潮汐流(「潮流」とも)という。潮汐という言葉でこれを指すこともある。 海面は潮汐力以外の要因でも上下し、気圧差や風によるものを気象潮という。代表的な気象潮は高潮(たかしお)である。気象潮と区別するため、潮汐力による潮汐を天体潮・天文潮ということがある。

    (Source: http://dbpedia.org/resource/Tide)

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