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Neap tides are sometimes referred to as quadrature tides. [8] Spring tides result in high waters that are higher than average, low waters that are lower than average, "slack water" time that is shorter than average, and stronger tidal currents than average. Neaps result in less extreme tidal conditions.
Spring tides occur at the second and fourth (last) quarters of the lunar phases. By contrast, during neap tides, when the Moon and Sun's gravitational force vectors act in quadrature (making a right angle to the Earth's orbit), the difference between high and low tides (neap range) is smallest. Neap tides occur at the first and third quarters ...
The dates of spring tides and neap tides, approximately seven days apart, can be determined by the heights of the tides on the classic tide tables: a small range indicates neaps and large indicates springs. This cycle of tides is linked to the phases of the moon, with the highest tides (spring tides) occurring near full moon and new moon.
The Venerable Bede discusses the tides in The Reckoning of Time and shows that the twice-daily timing of tides is related to the Moon and that the lunar monthly cycle of spring and neap tides is also related to the Moon's position.
The semi-diurnal tides go through one full cycle (a high and low tide) about once every 12 hours and one full cycle of maximum height (a spring and neap tide) about once every 14 days. The semi-diurnal tide (one maximum every 12 or so hours) is primarily lunar (only S 2 is purely solar) and gives rise to sectorial (or sectoral) deformations ...
In the absence of complications due to bathymetry, spring tides are exactly at the full and new moons and neap tides are exactly at the one-quarter and three-quarter moon. Every six hours the water also lowers or heightens; as such four tides are created: Low water spring tide High water spring tide Low water neap tide. High water neap tide
Tidal atlases may provide additional information for areas such as estuaries where it important to calculate tides away from the ports. Such information may include co-tidal range information [3] and time differences. [4] To calculate the rate at an intermediate tide between neap and spring, interpolation is required.
A perigean spring tide is a tide that occurs three or four times per year when a perigee (the point nearest Earth reached by the Moon during its 27.3-day elliptic orbit) coincides with a spring tide (when the Sun, the Moon, and Earth are nearly aligned every two weeks). [1]