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Lunitidal Interval
The lunitidal interval measures the time lag from lunar culmination to the next high tide at a given location. It is also called the high water interval (HWI). Sometimes a term is not used for the time lag, but instead the terms ''age'' or ''establishment'' of the tide are used for the entry that is in tide tables.''Beyond the Moon: A Conversational, Common Sense Guide to Understanding the Tides'', p. 89, by James Greig Mccully, World Scientific Publishing Company, Jan 13, 2006 Tides are known to be mainly caused by the Moon's gravity. Theoretically, peak tidal forces at a given location would concur when the Moon reaches the meridian, but a delay usually precedes high tide, depending largely on the shape of the coastline and the sea floor. Therefore, the lunitidal interval varies from place to place – from three hours over deep oceans to eight hours at New York Harbor. The lunitidal interval further varies within about 3h ± 30 minutes according to the lunar phase. (Th ...
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Culmination
In observational astronomy, culmination is the passage of a celestial object (such as the Sun, the Moon, a planet, a star, constellation or a deep-sky object) across the observer's local meridian. These events are also known as meridian transits, used in timekeeping and navigation, and measured precisely using a transit telescope. During each day, every celestial object appears to move along a circular path on the celestial sphere due to the Earth's rotation creating two moments when it crosses the meridian. Except at the geographic poles, any celestial object passing through the meridian has an upper culmination, when it reaches its highest point (the moment when it is nearest to the zenith), and nearly twelve hours later, is followed by a lower culmination, when it reaches its lowest point (nearest to the nadir). The time of ''culmination'' (when the object culminates) is often used to mean upper culmination. An object's altitude (''A'') in degrees at its upper culmin ...
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Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables can be used for any given locale to find the predicted times and amplitude (or " tidal range"). The predictions are influenced by many factors including the alignment of the Sun and Moon, the phase and amplitude of the tide (pattern of tides in the deep ocean), the amphidromic systems of the oceans, and the shape of the coastline and near-shore bathymetry (see '' Timing''). They are however only predictions, the actual time and height of the tide is affected by wind and atmospheric pressure. Many shorelines experience semi-diurnal tides—two nearly equal high and low tides each day. Other locations have a diurnal tide—one high and low tide each day. A "mixed tide"—two uneven magnitude tides a day—is a third regular category. ...
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Tide Table
Tide tables, sometimes called tide charts, are used for tidal prediction and show the daily times and levels of high and low tides, usually for a particular location. Tide heights at intermediate times (between high and low water) can be approximated by using the rule of twelfths or more accurately calculated by using a published tidal curve for the location. Tide levels are typically given relative to a low-water vertical datum, e.g. the mean lower low water (MLLW) datum in the US.Tidal Datums And Their Applications
NOAA Special Publication NOS CO-OPS 1, Silver Spring MD, June 2000.


Publication and scope

Tide tables are published in various forms, such as paper-based tables and tables available on the Internet. Most tide tables are calculated and published only ...
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Moon's Gravity
300px, Radial gravity anomaly at the surface of the Moon in mGal The acceleration due to gravity on the surface of the Moon is approximately 1.625 m/s2, about 16.6% that on Earth's surface or 0.166 . Over the entire surface, the variation in gravitational acceleration is about 0.0253 m/s2 (1.6% of the acceleration due to gravity). Because weight is directly dependent upon gravitational acceleration, things on the Moon will weigh only 16.6% (= 1/6) of what they weigh on the Earth. Gravitational field The gravitational field of the Moon has been measured by tracking the radio signals emitted by orbiting spacecraft. The principle used depends on the Doppler effect, whereby the line-of-sight spacecraft acceleration can be measured by small shifts in frequency of the radio signal, and the measurement of the distance from the spacecraft to a station on Earth. Since the gravitational field of the Moon affects the orbit of a spacecraft, one can use this tracking data to dete ...
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Meridian (astronomy)
In astronomy, the meridian is the great circle passing through the celestial poles, as well as the zenith and nadir of an observer's location. Consequently, it contains also the north and south points on the horizon, and it is perpendicular to the celestial equator and horizon. Meridians, celestial and geographical, are determined by the pencil of planes passing through the Earth's rotation axis. For a location ''not'' on this axis, there is a unique meridian plane in this axial-pencil through that location. The intersection of this plane with Earth's surface defines two '' geographical meridians'' (either one east and one west of the prime meridian, or else the prime meridian itself and its anti-meridian), and the intersection of the plane with the celestial sphere is the celestial meridian for that location and time. There are several ways to divide the meridian into semicircles. In one approach, the observer's upper meridian extends from a celestial pole and passes t ...
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Sea Floor
The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as seabeds. The structure of the seabed of the global ocean is governed by plate tectonics. Most of the ocean is very deep, where the seabed is known as the abyssal plain. Seafloor spreading creates mid-ocean ridges along the center line of major ocean basins, where the seabed is slightly shallower than the surrounding abyssal plain. From the abyssal plain, the seabed slopes upward toward the continents and becomes, in order from deep to shallow, the continental rise, slope, and shelf. The depth within the seabed itself, such as the depth down through a sediment core, is known as the "depth below seafloor". The ecological environment of the seabed and the deepest waters are collectively known, as a habitat for creatures, as the " benthos". Most of the seabed throughout the world's oceans is covered in layers of marine sediments. Cat ...
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New York Harbor
New York Harbor is a bay that covers all of the Upper Bay. It is at the mouth of the Hudson River near the East River tidal estuary on the East Coast of the United States. New York Harbor is generally synonymous with Upper New York Bay, which is enclosed by the New York City boroughs of Manhattan, Brooklyn, and Staten Island and the Hudson County, New Jersey, municipalities of Jersey City and Bayonne, although in colloquial usage it can sometimes expand to cover Upper and Lower New York Bay New York Harbor is one of the largest natural harbors in the world. Overview The harbor is fed by the waters of the Hudson River (historically called the North River as it passes Manhattan), as well as the Gowanus Canal. It is connected to Lower New York Bay by the Narrows, to Newark Bay by the Kill Van Kull, and to Long Island Sound by the East River, which, despite its name, is actually a tidal strait. It provides the main passage for the waters of the Hudson River as it em ...
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Lunar Phase
A lunar phase or Moon phase is the apparent shape of the Moon's directly sunlit portion as viewed from the Earth. Because the Moon is tidally locked with the Earth, the same hemisphere is always facing the Earth. In common usage, the four major phases are the new moon, the first quarter, the full moon and the last quarter; the four minor phases are waxing crescent, waxing gibbous, waning gibbous, and waning crescent. A lunar month is the time between successive recurrences of the same phase: due to the eccentricity of the Moon's orbit, this duration is not perfectly constant but averages about 29.5 days. The appearance of the Moon (its phase) gradually changes over a lunar month as the relative orbital positions of the Moon around Earth, and Earth around the Sun, shift. The visible side of the Moon is sunlit to varying extents, depending on the position of the Moon in its orbit, with the sunlit portion varying from 0% (at new moon) to nearly 100% (at full moon). Phenomenon ...
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Gravity Waves
In fluid dynamics, gravity waves are waves in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves. A gravity wave results when fluid is displaced from a position of equilibrium. The restoration of the fluid to equilibrium will produce a movement of the fluid back and forth, called a ''wave orbit''. Gravity waves on an air–sea interface of the ocean are called surface gravity waves (a type of surface wave), while gravity waves that are the body of the water (such as between parts of different densities) are called '' internal waves''. Wind-generated waves on the water surface are examples of gravity waves, as are tsunamis, ocean tides, and the wakes of surface vessels. The period of wind-generated gravity waves on the free surface of the Earth's ponds, lakes, seas and oceans are predominantly b ...
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Northern Hemisphere
The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined by humans as being in the same celestial sphere, celestial hemisphere relative to the invariable plane of the Solar System as Earth's North Pole. Due to Earth's axial tilt of 23.439281°, there is a seasonal variation in the lengths of the day and night. There is also a seasonal variation in temperatures, which lags the variation in day and night. Conventionally, winter in the Northern Hemisphere is taken as the period from the December solstice (typically December 21 UTC) to the March equinox (typically March 20 UTC), while summer is taken as the period from the June solstice through to the September equinox (typically on 23 September UTC). The dates vary each year due to the difference between the calendar year and the Year#Astronomical years, astronomical year. Within the Northern Hemisphere, oceanic currents can change the weather patterns that aff ...
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Almanac
An almanac (also spelled almanack and almanach) is a regularly published listing of a set of current information about one or multiple subjects. It includes information like weather forecasting, weather forecasts, farmers' sowing, planting dates, tide tables, and other table (information), tabular data often arranged according to the calendar. Celestial figures and various statistics are found in almanacs, such as the sunrise, rising and sunset, setting times of the Sun and Moon, dates of eclipses, hours of high and low tides, and religious festivals. The set of events noted in an almanac may be tailored for a specific group of readers, such as farmers, sailors, or astronomers. Name The etymology of the word is unclear. The earliest documented use of the word in something like its current sense is in Latin in 1267. Roger Bacon used it to mean a set of tables detailing movements of heavenly bodies including the Moon. It has been suggested that the word ''almanac'' derives fro ...
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Tide Clock
A tide clock is a specially designed clock that keeps track of the Moon's apparent motion around the Earth. Along many coastlines, the Moon contributes the major part (67%) of the combined lunar and solar tides. The exact interval between tides is influenced by the position of the Moon and Sun relative to the Earth, as well as the specific location on Earth where the tide is being measured. Due to the Moon's orbital prograde motion, it takes a particular point on the Earth (on average) 24 hours and 50.5 minutes to rotate under the Moon, so the time between high lunar tides fluctuates between 12 and 13 hours. A tide clock is divided into two roughly 6 hour tidal periods that show the average length of time between high and low tides in a semi-diurnal tide region, such as most areas of the Atlantic Ocean. Traditional mechanical tide clocks The bottom of the tide clock dial (6 o'clock position) is marked "low tide" and the top of the tide clock dial (12 o'clock position) is mark ...
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