Árapály

Árapály, in Hungarian often written as ár-apály, refers to the regular rise and fall of sea level caused by the gravitational forces of the Moon and the Sun on the Earth’s oceans. The term combines ár (flood) and apály (ebb). In common usage it denotes the overall phenomenon of tides, including the alternating high tides (dagály) and low tides (apály).

The mechanism involves gravitational attraction from the Moon and the Sun acting on the oceans. The Moon’s gravity creates bulges on the side of the Earth closest to it and on the opposite side, while the Sun’s gravity also pulls on the oceans. As the Earth rotates beneath these bulges, coastal areas experience rising and falling water levels. Most coastlines exhibit semidiurnal tides, with two high tides and two low tides within roughly a 24-hour period; other areas experience diurnal or mixed tides depending on coastline shape, ocean floor topography, and ocean basin resonances. The tidal range—the vertical difference between high and low water—varies significantly by location.

Measurements of arapály are conducted with tidal gauges and published in tide tables to assist navigation, coastal planning, and marine operations. Tides influence coastal ecosystems, sediment transport, and erosion, shaping intertidal habitats and nutrient cycles. Human activities include the development of tidal energy projects, flood defense planning, and harbor management, all of which must consider local tidal patterns and timing to ensure safety and efficiency.