How to distinguish the small tide in the spring tide

According to the intensity, there are only spring tides and small tides, as follows:

1, spring tide. The lunar new moon (around the first day) and the moon (around the fifteenth day) have the highest high tide and the lowest low tide.

2. Tides. The lowest high tide level and the highest low tide level appear in the upper chord (eighth and ninth day) and the lower chord (22nd and 23rd) of the lunar calendar.

According to the cause of formation

1, tide. The periodic fluctuation of sea level caused by the gravity of the moon, the sun and other celestial bodies is also called astronomical tide.

2, gas tide. The phenomenon of increasing water caused by strong weather systems such as atmospheric cyclones and typhoons is also called meteorological tide.

3. Surface tides. The elastic-plastic deformation of the solid earth caused by the tidal force of the sun and the moon is called the earth tide, also known as the earth tide.

Ocean tides, gas tides and surface tides interact with each other. Generally speaking, tides refer to ocean tides, unless otherwise specified.

Extended data

Reasons for the formation of spring tides and small tides

Yu Fujiang, a researcher at the Marine Environment Forecasting Center of the State Oceanic Administration, said that tides are mainly determined by the tidal force of the moon and the sun. Although the mass of the moon is smaller than that of the sun, its tidal force is about 2. 17 times higher than that of the sun. Whenever the moon and the sun move in a straight line, the tidal forces of the two celestial bodies will act in the same direction, and the fluctuation of seawater will inevitably increase.

This is the reason why people often say that "the fifteenth day of the first lunar month is on the rise". Astronomical tide is a normal astronomical tide phenomenon with a period of 18 weeks. 6 years, you can make predictions a few years in advance. Astronomical tides generally do not cause disasters, but they can cause water disasters in certain circumstances.

For example, when the river is full of water in flood season, it is difficult to retreat when it is supported by astronomical tide; If astronomical tide encounters a typhoon before and after landing, a storm surge will break out; If the water level of the river is low, the upstream range of the tide is expanded, and the degree of salt damage is aggravated, salt tide is formed.

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