in what way does the tide affect?

Question

In what way does the tide affect activites carried out on land or in air??

Answer 1

Tides Affect Earth's Rotation
Tides in the oceans cannot move freely because of the continents. They actually flow in a complex manner as shown below. Most often they circulate around nodes, very much the way a wave rotates around a cup as you oscillate it. In narrow, parallel-sided bodies of water the tides move as waves, for example in the South Atlantic.

Tides and History
The Boston Tea Party, December 16, 1773
Near Earth's perihelion: strong solar tides
Near lunar perigee: strong lunar tides
Full moon on December 13: spring tide
Overall effect: unusually large tidal range
On December 16, 1773, American colonists, frustrated by British tax policies, planned a dramatic protest. The merchant ships Dartmouth, Endeavour, and Beaver were in port with a cargo of tea, on which the colonists refused to pay tax. Negotiations with British authorities had broken down that afternoon, and the cargo was due to be seized at midnight if the tax was not paid. A group of colonists, dressed as Indians (a disguise which fooled nobody) boarded the ships about 6 P.M. and threw the tea overboard in the famous Boston Tea Party. But what happened to the tea after that?

Ideally, the tea should have been thrown overboard just after high tide, so the ebbing tide could carry it out to sea. In reality, because the colonists had only a few hours to stage their protest, they could not plan for the tides. The Boston Tea Party fell not just at low tide, but an exceptionally low tide at that. The incoming tide simply washed the tea ashore, and work parties with shovels cleaned it off the waterfront and threw it back into the harbor next day (pollution was not a concern for most people in those days!).

The Battle of Tarawa, November 20, 1943
Near Earth's perihelion: strong solar tides
Near lunar apogee: weak lunar tides
Near last-quarter moon: neap tide
Overall effect: unusually small tidal range
The effect of tides on the Boston Tea Party is a humorous footnote to history. The effect of tides on the battle for Tarawa during World War II was anything but. Tarawa was one of the easternmost Pacific islands held by the Japanese, and the assault was the first amphibious assault in the Pacific during World War II. Sketchy tide data for the island suggested a tidal range of about seven feet. However, there were puzzling rumors of periods when the tides on Tarawa almost ceased, a condition local mariners called a Adodging tide@.
Tarawa is a type example of an atoll, a flat-topped submarine mountain capped by coral. Most atolls, like Tarawa, have a wide shallow lagoon ringed by low coral islands.
The only island of consequence at Tarawa was one with an airfield. The plan was for Allied ships to stand offshore in deep water and send landing craft into the lagoon. The landing craft would go as far in as possible and discharge troops.


The invasion was set for November 20, 1943 when tide conditions were expected to be favorable. At low tide in the early morning, the bombardment would begin. As the tide rose and water levels in the lagoon reached 1.5 meters (five feet), landing craft would head ashore and by noon, at high tide, heavier craft could come ashore bringing tanks and supplies.

This isn't the sort of thing you can call off and reschedule if things go wrong, as they did. Once an attack is under way, the enemy knows your intentions. Any delay merely gives the enemy time to reinforce or escape.

Unfortunately, the rumors of almost-tideless periods at Tarawa were true. November 20 was near last-quarter moon, resulting in a neap tide. Military planners knew about the risks of neap tide but did not realize the moon was unusually far from earth as well, weakening its tidal effects even more. Also, the Earth was only seven weeks from perihelion, meaning solar tides were unusually strong as well.
The top diagram shows what planners expected. The bottom one shows what actually happened.


Landing craft hit bottom hundreds of meters offshore and the Marines had to wade ashore under heavy fire. Once ashore, they had to fight without assistance, because supply ships could not come in. For 48 hours, the tidal range was only 60 centimeters (two feet), and it was four days before the tidal range increased to normal. 1027 Marines were killed and 2292 wounded in the battle.

References
D. W. Olson, The Tide at Tarawa, Sky and Telescope V. 74, no. 5. p.526, November1987

Donald W. Olson and Russell L. Doescher, "The Boston Tea Party," Sky and Telescope, vol. 86 (Dec. 1993), 83–86
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Tides.

How they are generated.
How to calculate heights and times.
Staying afloat.

Knowledge of tidal movement is essential in undertaking safe navigation, especially in coastal waters. Simply, if there is insufficient depth of water, you will go aground.
Tides are the periodic rise and fall, or vertical movement of the levels of the worlds oceans. The difference between tides and tidal flows or currents must be appreciated. Tides affect only the depth of water. Tidal currents are the horizontal movement caused by tides, and effect the track and SOG of a vessel.
Tides are generated by the effect on the Earth's oceans by gravitational forces between the earth, the moon and the sun, by centrifugal force due to the Earth's rotation, and by centrifugal force due to the Earth's solar orbit. It should be appreciated that to scale, the oceans are no more than a layer of gladwrap on a soccer ball. | Earth | The moon has the greater gravitational effect, some 2.2 times greater than the sun at the Earth's surface. Because of it's fluidity, water tends to accumulate on the parts of the Earth's surface directly toward the moon and on the surfaces directly opposite the moon where centrifugal force of rotation exceeds the force of lunar gravity. Consequently, over all other areas the water levels are depleted. The regions of accumulation and depletion move over the surface as the position of the Moon varies relative to the Earth, mainly because of the Earth's daily rotation but also because of the Moon's orbital motion around the Earth, which is a period of 27.3 days, or a sidereal month. A lunar or synodic month, the period between one full moon and the next, is 29.5 days.The moon also rotates on its axis once every 29.5 days in the opposite direction to its orbit, giving the appearance from Earth that it does not rotate. The plane of the moon orbit around the Earth is generally in alignment with the plane of the Earth orbit around the Sun, i.e. it is tilted at 23.5° to the Earth polar axis.

Theoretically, if the Earth was completely covered in open deep water, two tidal waves 180 deg. apart and approx. 2 metres high would continuously circle the globe. However, the inertia of the water, the existence of continents, and effects associated with the water depth result in much more complicated behaviour. For the open ocean areas, tidal levels vary between zero and approx. 1 metre range. e.g. tidal range on mid Pacific islands is very small.

Because of the Earth's period of rotation, there are generally two high and two low tides per day at any given place, (semidiurnal tides),but they occur at times that change from day to day. The average interval between consecutive high tides is 12 hours 25 minutes. Tides occurring once daily are called diurnal. The gravitational effect of the Sun is similar and additive to that of the Moon. The tides of largest range or amplitude are called spring tides, and occur at New Moon, when the Moon and the Sun are in the same direction relative to Earth, ( in conjunction), and at Full Moon, when they are in opposite directions, ( in opposition). The tides of smallest range are called neap tides, and occur at intermediate phases of the Moon, at seven and a quarter days after new or full moon, in the first and last quarters, when the moon and sun are separated at 90 deg., ( in quadrature), and the gravitational effect of the sun diminishes that of the moon. | Phases of the moon | are caused by the varying amount of moon surface exposed to sunlight as viewed from a particular point on Earth.


Tides are most easily observed, and of greatest practical importance, along coastlines, where the amplitudes are exaggerated. When tidal motions run into the shallow waters of the continental shelf, their rate of advance is reduced, energy accumulates in a smaller volume, and the rise and fall is amplified. The details of tidal motions in coastal waters, particularly in channels, gulfs, and estuaries, depend on the details of coastal geometry and water-depth variation. Tidal amplitudes ( the contrast between spring and neap tides), and the variation of times of high and low tide all vary widely from place to place.
For these reasons, purely theoretical calculation of the times and heights of tides at a particular station is quite impossible. Tides are successfully predicted on the basis of accumulated observations of the tides at the place concerned. The periodical motions of the Moon and the Sun relative to the Earth contribute a range of variables at all locations, and occupy a cyclic period of 18.6 years, called the Saros cycle It is during this cyclic period that lowest astronomical tides, LAT, are recorded as the datum for tide predictions.
Other terrestrial occurrences affect tide levels. Strong onshore winds may increase tides in localised areas causing a tide to 'pile up'. Storm surge during cyclones is due to the combined effect of high wind velocity and low atmospheric pressure. High atmospheric pressure can suppress tide levels. Seismic activity can have an effect over large areas. The effect of a deep cyclone in the Coral Sea will generate abnormal local coastal swells up to a week later.
The study of tidal predictions is part of the science of hydrography, and comprehensive data is published annually and on a web site by the | National Tidal Facility | based at Flinders University, Adelaide. State authorities each have hydrographic departments, and publish annual tidal data books. | Tidal Predictions. | See also | Tides. |


Tidal Terminology. Refer to pages 201 - 203 of the 2007 tide book.

Reading of Tide Tables. Gladstone. Refer to pages 135 to 137 of the 2007 tide book.


Tidal Datum. This is the lowest astronomical tide recorded over a solar cycle of 18.6 years, and is the datum or reference point for all soundings on charts and tidal heights.This fact is clearly noted in the tide tables. The height of a tide must be added to the charted depth below this datum to obtain the actual depth at a particular time.
Standard ports are those which have the tide time and heights tabulated for every day of the year.
See p. 204 of the 2007 tide book.
Secondary ports are those whose tide time and heights are obtained by applying corrections to the associated standard port. Refer to p. 205 - 210 of the 2007 tide book. Note that some Qld. coastal places experience diurnal tides.
Intermediate tide heights for all ports can be calculated using the Standard Tidal Curve tables.
Refer p. 211 - p. 212 of the 2007 tide book. Note that the vertical scale of the curve tables is tidal range, not tide height, and the previous or next low tide height must be added to obtain depth of water. Tidal ranges between the standard curves can be approximated.
Alternatively, heights can be calculated using the ' Rule of 12ths.' Tidal range covers a period of approx. six hours. Determine the range of the tide and divide by 12. Assuming a low tide, in the first hour, the tide would rise 1/12th of the range, in the second hour 2/12ths, in the third hour 3/12ths, in the fourth hour 3/12ths, in the fifth hour 2/12ths, and in the last hour 1/12th. Total 12/12ths.
This method may be demonstrated diagramatically. On a circle, the diameter of which represents tidal range, mark off 30° angles and construct horizontal chords. The intercepts on the vertical diameter will be in the ratio of 1:2:3:3:2:1.