The Moon phase also influences the tidal range. The solar tide coincides with the lunar tide during certain lunar phases because the Sun and Moon are aligned with Earth, and their gravitational forces combine to draw the ocean's water in the same direction. Spring tides or king tides are the names given to these tides. At neap tide, when the Moon is new or full, the ebb tide is higher than the flood tide.
At first glance, it might seem that a full moon would cause high tides every time it was near perigee (the closest point to Earth in its orbit), but this isn't true because some times there are two perigees and other times there is only one. A full moon has both perigee and apogee (farthest point from Earth in its orbit). Thus, a full moon can either cause high tides at both perigee and apogee, or only at perigee. If you look up the Moon's position for any given date, you can see which parts of the cycle it will be causing high tides at.
The most important factor affecting the height of the tide is the angle made by the Moon's center of mass and gravity with respect to Earth's surface. At perigee, this angle is 90 degrees, so all of Moon's weight is falling toward Earth. As a result, the sea level increases until it reaches a maximum value called the spring tide.
Tides coincide with the moon's gravitational pull as it circles the Earth. The sun causes a lower tide. Spring tides occur when the solar and lunar tides coincide during new and full moons, resulting in higher-than-normal tidal ranges. Neap tides occur when the lunar tide and the resulting low tide coincide with the moment that the moon is farthest from the Earth.
The direction of the ebb and flow of the sea depends on where you are standing with respect to the wind and the moon. If the wind is coming from one direction and the moon from another, then we say that the water is flowing from east to west across the beach. If the wind is coming from two different directions, then the water flows into one area of the beach and out another. Tides can be either high or low depending on which way the water is going. A high tide occurs when the water is flowing out to sea; a low tide occurs when the water is flowing back in toward the ocean. The height of the tide varies depending on where you are standing on the planet. If you are standing on an island, for example, then you will see that the tide is much higher than if you were standing on the coast of California.
Some places experience tidal streams, which are fast-moving currents of water that race across the shoreline when the tide is high.
Spring tides occur when the Earth, Sun, and Moon are all in alignment, increasing the gravitational pressure on the seas. The Sun and Moon are sometimes on different sides of the Earth, while other times they are on the same side. When this happens, we call it an annular tide pattern.
These tides usually cause high water at both springs and neaps. But because the direction of the force from the Sun and Moon is opposite at each spring and neap, the heights of the waters change throughout the day. The highest point on the sea floor is usually reached about an hour after sunrise or an hour before sunset. The lowest point is usually about an hour after midnight or just before dawn.
The alignment of the Earth, Sun, and Moon occurs approximately every 18.5 years. So there are about 18.5-year cycles for each spring and neap tide to rise and fall. These cycles can be seen in many natural phenomena that are not related to land masses, such as ocean currents and ice ages. The current phase of these orbits is called "tide".
At full moon, when the round face of the Moon is presented to the Earth, we get lunar tides. At first glance, this might lead to the conclusion that the height of the oceans must also be at a maximum at this time.
Water levels and tides When the sun, moon, and Earth are in alignment (during the new or full moon), the solar tide adds to the lunar tide, resulting in extra-high high tides and very low low tides, both known as spring tides. The alignment of these objects is called a tidal phase. The strength of the combined tides is called the amplitude.
The gravitational effects of the sun and moon on water are called tides. The term "tide" refers to the height of the water level alongshore and offshore, which varies during each cycle of the moon, relative to some fixed point on the land. Thus, there are two types of tides: astronomical and mechanical. Astronomical tides are caused by the gravitational interactions between the earth, moon, and sun; mechanical tides are caused by surface currents of the ocean. As the name suggests, astronomical tides vary with respect to time based on the position of the moon and sun, while mechanical tides are relatively constant throughout the day.
Mechanical tides result from wind and current moving across the surface of the sea. These movements set up waves that rise and fall with each wave having its peak height at the midpoint between the height of the sea at sunrise and sunset. The difference between the average height of the water at midday and the average height at midnight is called the mean sea level.