– Jani Hitesh – Prajapati Dharmesh Prajapati Shivam TIDES

Tides Caused by the combined gravitational effects of the sun and moon, with the moon having the major effect – influenced by terrestrial gravity earth’s rotation land masses weather systems

Tides - Semi-Diurnal Tide Consider the earth to be stationary and covered with a layer of water. Assume that the position of the moon is fixed such that it has zero declination

Tides - Semi-Diurnal Tide On the side of the earth nearest the moon there is a net force towards the moon whilst on the opposite side there is a net force away from the moon. The small net forces at the North and South poles will be towards the centre of the earth.

Tides - Semi-Diurnal Tide At the two points on the equator, nearest and farthest from the moon there will be permanent high water. At right angles to these points a band of low water will lie along the meridian on either side of the earth

Tides - Semi-Diurnal Tide When the moon moves into perigee (closest point to the earth during the moon’s elliptical orbit) the high waters will be higher and the low waters will be lower. The opposite effect occurs when the moon moves out to apogee (most distant point) These minimum and maximum tides are known as perigean and apogean respectively

Tides - Semi-Diurnal Tide When the earth rotates the four tides, two high and two low, move around the earth, in a 24 hour period. This is known as a semi-diurnal tide the poles have a permanent low tide

Tides - Diurnal Tide The moon's declination causes inequalities in the tides that occur. successive high tides at a point on the earth with a latitude equal to X (and Y) will NOT be equal. – The high tide at X will not be as high as that at Y

Tides - Diurnal Tide At all points on the earth where the latitude on earth is greater than the moon’s co-declination, there is only one high tide and one low tide per day. This is known as the diurnal tide The form of tide varies between the extremes of diurnal and semi-diurnal, with those exhibiting both characteristics being known as 'mixed' Moon’s co-declination

Tides - Spring Tide The sun has a similar tide producing effect on the earth to that of the moon. However the forces involved are not as great. At new and full moon the sun, moon and earth are nearly in a straight line. The tide raising forces act together to produce tides with a large range. These tides occur fortnightly and are called spring tides

Tides - Neap Tide At the moon's first and last quarter the moon's tide raising force is to some extent counteracted by the sun's tide raising force producing tides with a small range. These tides are called neap tides (neap being high water at its lowest value).

Tide Gauges - Tide Board merely a vertical staff with a broader face than a levelling staff. This may be graduated every 5 or 10 centimetres, according to the accuracy required. The tide board is often difficult to read due to the surface chop or wave action

Tide Gauges - Float Gauge A float is attached to the bottom of a staff. The staff is then held in a box which is fixed in a vertical position. Only the bottom of the box is open to the sea. The float rises and falls with the tide, the staff running up and down through guides on the inside of the box. The staff can be read through a special inspection opening in the side of the box.

Tide Gauges - Automatic Tide Gauge normally established permanently at an official tide station. The tidal fluctuations are recorded on a chart attached to a drum which revolves with time The gauge may need to be visited only once every seven days to change the paper chart and reset the drive mechanism, i.e. wind the clock