Sea state

The term sea state ( erroneously also: swell ) generally refers to a surface appearance of the oceans and seas in the form of waves. This is the current generated by the wind ( wind sea ), and the elderly or the sea area considered in supported by elsewhere ( swell ) irregular, randomly distributed movement of the water surface.

Sea and swell

Under the direct influence of the generating wind field standing, part of the swell and wind sea is called, in comparison to the peak wave trough mountains. When the wind stops remain the waves of wind sea are made first and then ebbing slowly. The wave components with long wavelength can also attach to areas inside fort, where no (or other ) wind blows. This residual waves are called swell and are flat and round. Meeting, two wave systems from different directions results in a cross sea.

Wave height

The wave height is defined as the vertical distance between the wave trough and wave crest and results from the factors:

For all three factors, that the wave height at the beginning increases sharply, then slowly approaching a saturation value. One speaks of a " mature wind sea ". So weak swell can be found with little wind, when wind has just been freshened up and on the lee shore (which is closer to the wind ). Heavy seas can be found in a strong wind that blows on the Luvküste for days.

The wavelength ( the distance from wave crest to wave crest ) results from the temporal distance between two wave crests ( wave period T):

The propagation velocity of water waves increases with the wavelength. A wave with L = 100 m shifts, for example, 45 km / h, one with L = 200 m shifted by 63 km / h Rolling waves can thus traverse large sea areas in a short time and thus serve as a messenger of Approaching the wind.

Waves on the open sea and about 30 m high, the wavelengths can reach up to 1,000 m. It is also significant, the slope of a wave: a low but steep wave with short shaft distance ( wavelength) can be very uncomfortable; but a much higher plane wave with a large shaft distance can be quite gentle.


In correspondence to the wind force on the Beaufort sea state denotes a unit in the maritime sector.

After the German captain Peter Petersen Seegangsskala includes the strengths from 0 to 9 It was published until 1927, and since 1939 internationally recognized and implemented by the World Meteorological Organization.