What caused the spring tide in Qiantang River?

The following is a comprehensive.

Tide is a natural phenomenon in coastal areas. In ancient times, it was called "Tide" during the day and "Sunseeker" at night, both of which were called "Tide". Its occurrence is related to the sun and the moon, and also corresponds to the traditional lunar calendar in China. On the first day of the first lunar month, the sun and the moon are on one side of the earth, so tidal force is the largest, which will cause a "spring tide". Near the 15th or 16th day of the first lunar month, the sun and the moon are on both sides of the earth, and the tidal force of the sun and the moon will also cause "spring tide". When the phases of the current month are the first quarter moon and the second quarter moon, that is, August and 23rd of the lunar calendar, the tidal force of the sun and the tidal force of the moon cancel each other out, so a "small tide" occurs. Therefore, there is a saying in agricultural proverbs that "the spring tide begins on the fifteenth day of the first lunar month, and beaches can be seen everywhere on the 23rd of the eighth lunar month". In addition, there was a climax on the first day. Because the moon moves eastward more than 13 degrees on the celestial sphere every day, which is about 50 minutes in total, that is, the transit time of the moon (1 lunar day =24: 50) is delayed by about 50 minutes every day, (there will be tides in the next transit, usually twice a day), so the time of high tide is also delayed by about 50 minutes every day.

However, due to the complexity of the movements of the moon and the sun, the spring tide may sometimes be delayed by one or several days, and the climax during lunar day is often one hour or several hours later than the transit time on the moon. In some places, the tide will rise as soon as the lunar calendar is over.

The gravity of the sun and the moon plays such a great role in the water (liquid) on the earth, and also in the solid continent of the earth's crust, so "land tide" may lead to earthquakes, so the moon phase should be considered in earthquake prediction;

The gravity of the sun and the moon will also have a great effect on the atmosphere (gas) on the earth, and a "atmospheric tides" will occur, which will cause changes in atmospheric convection and atmospheric movement, as well as climate change. This contradicts the traditional view that climate change has nothing to do with the moon. Therefore, meteorologists suggest that the moon phase should be considered when making weather forecast.

According to modern science, the attraction of the sun and the moon may also act on the liquid in human body or organism, forming mysterious "biological tide" and "human tide". Some Japanese scientists are studying this problem. There is an ancient saying in China that "you can't escape from the first day, but you can't escape from the fifteenth day", which is also a vivid portrayal of the mysterious biological tide and human tide that may lead to the aggravation of human or other biological diseases or mental changes.

Working people in China have summed up thousands of years' experience and put forward many tidal calculation methods (tidal pushing time), such as the eight-point tidal calculation method, for example, the concise formula is:

High tide =0.8h×[ Lunar date-1 (or 16)]+ high tide interval.

When the above formula can be regarded as one-day high tide, for the normal semidiurnal tide sea area, add or subtract 12: 25 (or add or subtract 12: 24 for calculation convenience) to get another high tide time. If you add or subtract 6: 00 and 12 points, you can get the time of low tide-low tide.