Height of large sea waves changes according to month

Published: Saturday, May 30, 2009, 13:02 [IST]
 

Washington, May 30 (ANI): Scientists have used a 'non- seasonal' statistical model to determine that the height of large waves in the sea can change according to the month.

"Anybody who observes waves can see that they are not the same height in winter and summer, but rather that their height varies over time, and we have applied a 'non- seasonal' statistical model in order to measure extreme events such as these," said Fernando J. Mendez, an engineer at the Institute of Environmental Hydraulics at the University of Cantabria, Spain.

The new model can chart the pattern of extreme waves "with a greater degree of reliability", by studying 'significant wave height' (Hs) in relation to a specific return period.

The Hs is the representative average height of the sea, provided by buoys, and the return period is the average time needed for the event to happen.

For example, if a wave height of 15 meters is established at a certain point on the coast with a return period of 100 years, this means that, on average, a wave of 15 meters could reach this point once every 100 years.

"This can be very useful when it comes to building an oil platform in the sea or a particular piece of coastal infrastructure," explained Mendez.

The researchers have used data recorded between 1984 and 2003 by five coastal buoys located near the cities of Bilbao, in Vizcaya; Gijon, in Asturias; La Coruna, Cadiz and Valencia in order to demonstrate the validity of their model.

The results show that extreme Hs values vary according to location and the month of the year.

The results showed a similar seasonal variation between waves in Bilbao and Gijon, with waves being less than four meters high between May and September, but increasing after this to reach an average height of seven meters between December and January.

The period of large waves in La Coruna extends from October to April, because of the city's westerly position and resulting exposure to more prolonged winter storms.

The Atlantic coast of Cadiz, meanwhile, reflects the characteristic calm of this area of sea between July and September, with Hs values below two meters.

The figures for December and January, however, can vary a great deal from one year to another, reaching wave heights in excess of six meters.

According to Melisa Menendez, one of the study's authors, "All these data are of vital importance in terms of coastal management, since they can establish the risk of flooding and are indispensable for the carrying out of marine construction work."

"In addition, they make it possible to calculate the likelihood of a maritime storm occurring," she added. (ANI)


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