Tidal Table of Weihai 201August 5

Tidal schedule of Weihai 2065438+August 5, 2008:

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Short for tide forecast table. It predicts the daily tides in some coastal areas in the future.

In shipping, some waterways and ports can only sail and enter and leave the port before and after the high tide; In the military, it is sometimes necessary to consider and master the tidal situation in order to choose a favorable landing place and time.

In terms of production, coastal fisheries, aquaculture, agriculture, salt industry, resource development, port engineering construction, surveying, environmental protection and tidal power generation. We must master the law of tidal changes. Tide tables serve these aspects.

Tide tables generally include daily forecast tables of major ports (usually including the time and height of high tide and low tide, hourly tidal level of some ports), differential ratio of affiliated ports, tidal information and calculation of tidal level at any time.

Port. In the ports where semidiurnal tides are dominant, the tidal characteristic values of each port are usually listed, such as average high tide interval, average high tide rise (average high tide of spring tide) and average low tide rise (average high tide of small tide).

In ports dominated by diurnal tides, the tidal characteristic values of return tides and vernal equinox tides are generally listed, which can be used to calculate the approximate tidal time and tidal level height of each port and understand the tidal characteristics of its ports.

The calculation of any tidal time or tide level is usually accompanied by charts and tables to facilitate the calculation. These charts and tables are used to calculate the tide level at any time between high tide and low tide or at any time when any tide level appears when high tide and low tide are known.

In addition, some tide tables are accompanied by the harmonic constants of the main tidal components of each port, or briefly introduce the tidal current in the nearby waters.

Extended data:

Through long-term practice and observation, people find that the sea water fluctuates regularly, and the fluctuation time and height change periodically, so people call this phenomenon sea water fluctuation tide.

With the fluctuation of seawater and the rise and fall of water level, the horizontal flow of seawater appears, which is called tidal current. Sea water fluctuates periodically, for example, there are two big tides and two small tides in a day.

Through long-term practice and observation, it is found that the daily high tide mostly occurs at the mid-day of the moon (that is, near 1, which is over the local time). The low tide time is before and after the moon rises and sets, and the daily high (low) tide time is about 48 minutes later.

That is 48 minutes (0.8 hours) every night. The two big tides every month are near the first and fifteenth day of the lunar calendar, and the two small tides are near the seventh and eighth, twenty-second and twenty-third day of the lunar calendar.

It is also found that tidal phenomena are closely related to the relative movements of the moon, the sun and the earth. The earth moves around the sun in a certain orbit, and the moon moves around the earth in a certain orbit. There is a certain attraction and centrifugal force between them, which is the basic factor of tidal phenomenon.

However, the main reason for the actual tidal fluctuation is the attraction of the moon to the earth (surface layer), followed by the attraction of the sun to the earth. The role of the sun is small, about 2/5 of that of the moon. Because the moon is close to the earth, it plays a greater role.

According to scientific speculation, the moon revolves around the earth once a month (a little more than 29.5 days). When the moon, the sun and the earth are in a straight line, the tides fluctuate the most.

This is the time when the new moon meets the full moon (the first and fifteenth day of the lunar calendar), and the tidal fluctuation is the smallest when the sky, the moon and the earth form a right triangle. This is the time of the first quarter moon (the seventh and eighth day of the lunar calendar) and the second quarter moon (the 22nd and 23rd day of the lunar calendar).

However, in fact, the formation time of high tide and low tide is not exactly the above time, because the shape of the earth is very complicated, so the maximum tide and minimum tide appear in various places a few days later than in theory.

For example, the tidal fluctuation in the coastal area of Shandong Peninsula is the largest on the third and eighteenth days, while the tidal fluctuation is the smallest around the tenth and twenty-fifth days. Due to the rotation of the earth itself, the relative position between a point on the earth and the moon is changing at any time.

This change is a cycle every day (about 24: 48 in the sun). Every 24: 48, there are two high tides and two low tides. It takes about 6: 00 12 from high tide to low tide, and about 12: 24 from the first high tide to the second high tide.

References:

Tidal Curve —— China Maritime Network