historical tide and swell table of napier pdf

Historical tide and swell table of napier pdf

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Published: 29.03.2021

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Tide predictions

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The meteorological conditions that can have an effect are described in meteorological effects on tides. Search criteria. Click on an orange marker on the map below to see a listing of the daily predictions of the times and heights of high and low waters available for download for that location. The zero points of the predicted tide heights are described here.

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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. 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. Tides vary on timescales ranging from hours to years due to a number of factors, which determine the lunitidal interval. To make accurate records, tide gauges at fixed stations measure 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 shape of the solid part of the Earth is affected slightly by Earth tide , though this is not as easily seen as the water tidal movements.

Oscillating currents produced by tides are known as tidal streams. The moment that the tidal current ceases is called slack water or slack tide.

The tide then reverses direction and is said to be turning. Slack water usually occurs near high water and low water. But there are locations where the moments of slack tide differ significantly from those of high and low water. Tides are commonly semi-diurnal two high waters and two low waters each day , or diurnal one tidal cycle per day.

The two high waters on a given day are typically not the same height the daily inequality ; these are the higher high water and the lower high water in tide tables.

Similarly, the two low waters each day are the higher low water and the lower low water. The daily inequality is not consistent and is generally small when the Moon is over the Equator. Tidal constituents are the net result of multiple influences impacting tidal changes over certain periods of time.

Primary constituents include the Earth's rotation, the position of the Moon and Sun relative to the Earth, the Moon's altitude elevation above the Earth's Equator, and bathymetry. Variations with periods of less than half a day are called harmonic constituents.

Conversely, cycles of days, months, or years are referred to as long period constituents. Tidal forces affect the entire earth , but the movement of solid Earth occurs by mere centimeters. In contrast, the atmosphere is much more fluid and compressible so its surface moves by kilometers, in the sense of the contour level of a particular low pressure in the outer atmosphere. In most locations, the largest constituent is the principal lunar semi-diurnal , also known as the M2 tidal constituent or M 2 tidal constituent.

Its period is about 12 hours and Simple tide clocks track this constituent. The lunar day is longer than the Earth day because the Moon orbits in the same direction the Earth spins. The Moon orbits the Earth in the same direction as the Earth rotates on its axis, so it takes slightly more than a day—about 24 hours and 50 minutes—for the Moon to return to the same location in the sky.

During this time, it has passed overhead culmination once and underfoot once at an hour angle of and respectively , so in many places the period of strongest tidal forcing is the above-mentioned, about 12 hours and 25 minutes. The moment of highest tide is not necessarily when the Moon is nearest to zenith or nadir , but the period of the forcing still determines the time between high tides.

Because the gravitational field created by the Moon weakens with distance from the Moon, it exerts a slightly stronger than average force on the side of the Earth facing the Moon, and a slightly weaker force on the opposite side.

The Moon thus tends to "stretch" the Earth slightly along the line connecting the two bodies. The solid Earth deforms a bit, but ocean water, being fluid, is free to move much more in response to the tidal force, particularly horizontally see equilibrium tide.

As the Earth rotates, the magnitude and direction of the tidal force at any particular point on the Earth's surface change constantly; although the ocean never reaches equilibrium—there is never time for the fluid to "catch up" to the state it would eventually reach if the tidal force were constant—the changing tidal force nonetheless causes rhythmic changes in sea surface height. When there are two high tides each day with different heights and two low tides also of different heights , the pattern is called a mixed semi-diurnal tide.

The semi-diurnal range the difference in height between high and low waters over about half a day varies in a two-week cycle. Approximately twice a month, around new moon and full moon when the Sun, Moon, and Earth form a line a configuration known as a syzygy [10] , the tidal force due to the Sun reinforces that due to the Moon. The tide's range is then at its maximum; this is called the spring tide. It is not named after the season , but, like that word, derives from the meaning "jump, burst forth, rise", as in a natural spring.

At these points in the lunar cycle, the tide's range is at its minimum; this is called the neap tide , or neaps.

Spring tides result in high waters that are higher than average, low waters that are lower than average, " slack water " time that is shorter than average, and stronger tidal currents than average. Neaps result in less extreme tidal conditions.

There is about a seven-day interval between springs and neaps. The changing distance separating the Moon and Earth also affects tide heights. When the Moon is closest, at perigee , the range increases, and when it is at apogee , the range shrinks. Even at its most powerful this force is still weak, [12] causing tidal differences of inches at most. These include solar gravitational effects, the obliquity tilt of the Earth's Equator and rotational axis, the inclination of the plane of the lunar orbit and the elliptical shape of the Earth's orbit of the Sun.

A compound tide or overtide results from the shallow-water interaction of its two parent waves. Because the M 2 tidal constituent dominates in most locations, the stage or phase of a tide, denoted by the time in hours after high water, is a useful concept.

Lines of constant tidal phase are called cotidal lines , which are analogous to contour lines of constant altitude on topographical maps , and when plotted form a cotidal map or cotidal chart. Semi-diurnal and long phase constituents are measured from high water, diurnal from maximum flood tide. This and the discussion that follows is precisely true only for a single tidal constituent.

For an ocean in the shape of a circular basin enclosed by a coastline, the cotidal lines point radially inward and must eventually meet at a common point, the amphidromic point. The amphidromic point is at once cotidal with high and low waters, which is satisfied by zero tidal motion. The rare exception occurs when the tide encircles an island, as it does around New Zealand, Iceland and Madagascar.

Tidal motion generally lessens moving away from continental coasts, so that crossing the cotidal lines are contours of constant amplitude half the distance between high and low water which decrease to zero at the amphidromic point. For a semi-diurnal tide the amphidromic point can be thought of roughly like the center of a clock face, with the hour hand pointing in the direction of the high water cotidal line, which is directly opposite the low water cotidal line.

High water rotates about the amphidromic point once every 12 hours in the direction of rising cotidal lines, and away from ebbing cotidal lines. This rotation, caused by the Coriolis effect , is generally clockwise in the southern hemisphere and counterclockwise in the northern hemisphere. The difference of cotidal phase from the phase of a reference tide is the epoch. In the North Atlantic, because the cotidal lines circulate counterclockwise around the amphidromic point, the high tide passes New York Harbor approximately an hour ahead of Norfolk Harbor.

South of Cape Hatteras the tidal forces are more complex, and cannot be predicted reliably based on the North Atlantic cotidal lines. Investigation into tidal physics was important in the early development of celestial mechanics , with the existence of two daily tides being explained by the Moon's gravity.

Later the daily tides were explained more precisely by the interaction of the Moon's and the Sun's gravity. Seleucus of Seleucia theorized around BC that tides were caused by the Moon. The influence of the Moon on bodies of water was also mentioned in Ptolemy 's Tetrabiblos. In De temporum ratione The Reckoning of Time of Bede linked semidurnal tides and the phenomenon of varying tidal heights to the Moon and its phases.

Increasing tides are called malinae and decreasing tides ledones and that the month is divided into four parts of seven or eight days with alternating malinae and ledones. To the north of Bede's location Monkwearmouth the tides are earlier, to the south later. Medieval understanding of the tides was primarily based on works of Muslim astronomers , which became available through Latin translation starting from the 12th century.

Simon Stevin in his De spiegheling der Ebbenvloet , The theory of ebb and flood, dismissed a large number of misconceptions that still existed about ebb and flood. Stevin pleaded for the idea that the attraction of the Moon was responsible for the tides and spoke in clear terms about ebb, flood, spring tide and neap tide , stressing that further research needed to be made.

In Johannes Kepler also correctly suggested that the gravitation of the Moon caused the tides, [d] which he based upon ancient observations and correlations. The resulting theory, however, was incorrect as he attributed the tides to the sloshing of water caused by the Earth's movement around the Sun.

He hoped to provide mechanical proof of the Earth's movement. The value of his tidal theory is disputed.

Galileo rejected Kepler's explanation of the tides. Isaac Newton — was the first person to explain tides as the product of the gravitational attraction of astronomical masses.

His explanation of the tides and many other phenomena was published in the Principia [28] [29] and used his theory of universal gravitation to explain the lunar and solar attractions as the origin of the tide-generating forces. Maclaurin used Newton's theory to show that a smooth sphere covered by a sufficiently deep ocean under the tidal force of a single deforming body is a prolate spheroid essentially a three-dimensional oval with major axis directed toward the deforming body.

Maclaurin was the first to write about the Earth's rotational effects on motion. Euler realized that the tidal force's horizontal component more than the vertical drives the tide. In Jean le Rond d'Alembert studied tidal equations for the atmosphere which did not include rotation. Attempts were made to refloat her on the following tide which failed, but the tide after that lifted her clear with ease. Whilst she was being repaired in the mouth of the Endeavour River Cook observed the tides over a period of seven weeks.

At neap tides both tides in a day were similar, but at springs the tides rose 7 feet 2. Pierre-Simon Laplace formulated a system of partial differential equations relating the ocean's horizontal flow to its surface height, the first major dynamic theory for water tides.

The Laplace tidal equations are still in use today. William Thomson, 1st Baron Kelvin , rewrote Laplace's equations in terms of vorticity which allowed for solutions describing tidally driven coastally trapped waves, known as Kelvin waves. Based on these developments and the lunar theory of E W Brown describing the motions of the Moon, Arthur Thomas Doodson developed and published in [36] the first modern development of the tide-generating potential in harmonic form: Doodson distinguished tidal frequencies.

From ancient times, tidal observation and discussion has increased in sophistication, first marking the daily recurrence, then tides' relationship to the Sun and moon. Pytheas travelled to the British Isles about BC and seems to be the first to have related spring tides to the phase of the moon. In the 2nd century BC, the Hellenistic astronomer Seleucus of Seleucia correctly described the phenomenon of tides in order to support his heliocentric theory.

Swell (ocean)

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. 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.


Tide tables and solunar charts for Napier: high tides and low tides, surf reports, sun and moon rising and setting times, lunar phase, fish activity and weather.


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Deterministic analysis of local tsunami generated by subduction zone earthquakes demonstrates the potential for extensive inundation and building damage in Napier, New Zealand. We present the first high-resolution assessments of tsunami inundation in Napier based on full simulation from tsunami generation to inundation and demonstrate the potential variability of onshore impacts due to local earthquakes. Inundation due to single-segment or splay fault rupture is relatively limited despite the magnitudes of M W 7. These new data on potential flow depth, arrival time and flow kinematics provide valuable information for tsunami education, exposure analysis and evacuation planning. This is a preview of subscription content, access via your institution.

The effects of Water Temperature. Fish are cold blooded, which means their metabolism is strongly influenced by the temperature of their surrounding environment. Fish want to stay comfortable. Consequently, even a small change or break will cause fish to move from one location to another.

The effects of Water Temperature. Fish are cold blooded, which means their metabolism is strongly influenced by the temperature of their surrounding environment. Fish want to stay comfortable.

Tide predictions

The effects of Water Temperature. Fish are cold blooded, which means their metabolism is strongly influenced by the temperature of their surrounding environment. Fish want to stay comfortable. Consequently, even a small change or break will cause fish to move from one location to another. In general, this behavior varies for each species and place, so we can not specify an ideal water temperature, however as a general rule we will try to avoid the temperatures abnormally cold in summer and too warm in winter. Remember, look for the comfort zones and you will find the fish.

A swell , also sometimes referred to as ground swell , in the context of an ocean , sea or lake , is a series of mechanical waves that propagate along the interface between water and air under the predominating influence of gravity' and thus are often referred to as surface gravity waves. These surface gravity waves have their origin as wind waves , but are the consequence of dispersion of wind waves from distant weather systems , where wind blows for a duration of time over a fetch of water, and these waves move out from the source area at speeds that are a function of wave period and length. More generally, a swell consists of wind-generated waves that are not greatly affected by the local wind at that time. Swell waves often have a relatively long wavelength , as short wavelength waves carry less energy and dissipate faster, but this varies due to the size, strength, and duration of the weather system responsible for the swell and the size of the water body, and varies from event to event, and from the same event, over time. Occasionally, swells that are longer than m occur as a result of the most severe storms.

Главная разница между элементами… разница между… нужно найти число… - Подождите! - сказала .

Tsunami inundation in Napier, New Zealand, due to local earthquake sources

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Все глобальное электронное сообщество было обведено вокруг пальца… или так только. ГЛАВА 5 Куда все подевались? - думала Сьюзан, идя по пустому помещению шифровалки.  - Ничего себе чрезвычайная ситуация. Хотя большинство отделов АНБ работали в полном составе семь дней в неделю, по субботам в шифровалке было тихо. По своей природе математики-криптографы - неисправимые трудоголики, поэтому существовало неписаное правило, что по субботам они отдыхают, если только не случается нечто непредвиденное.

Коммандер, пытаясь приоткрыть дверь, прижал лицо вплотную к узенькой щелке. - Господи Боже мой, Сьюзан, с тобой все в порядке. Она встала на ноги и расправила платье. - Все обошлось. Сьюзан огляделась. Третий узел был пуст, свет шел от работающих мониторов.

1 comments

  • Evie W. 01.04.2021 at 22:15

    Nz tides auckland.

    Reply

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