Abnormal waves: science tries to predict them

Anomalies: Thanks to the new research, they can be predicted probabilistically. Crucial information for sailors and oil rigs

For sailors, and more recently for oil rigs, the main question is “How high are the storm surge?” Over the years, direct experience and the increasingly numerous measurements, both from satellites and from oceanographic buoys, have pushed potential values ​​of wave heights higher and higher.

During a January 2014 storm in the North Atlantic, it was estimated (data from the European Center for Meteorology’s Medium-Term Forecast Model, ECMWF, Reading, UK) that the “significant height”, i.e. the energy scale of the storm touched 20 metres. However, this means that there were definitely single waves above 35 meters.

The analysis that followed the event, which was attended by Alves Benitazzo and Luigi Cavalieri of the Marine Sciences Institute of the National Research Council (Cnr-Ismar) in Venice, published in Scientific Reports titled “Observing a giant wave beam on the ocean surface”, has shown that it is possible to predict these” Anomalies” beforehand, but only in a probabilistic sense.

“Characterization of waves of this height requires advanced techniques of multidimensional nonlinear analysis, which, starting with information about the active state of the sea, is able to explain the subsequent appearance of these anomalous waves, which is, as in two or three times as high waves , a significant rise can be created in the middle of a storm,” Cavalieri explains. Driven by the winds, the swollen waves that followed brought waves of extraordinary energy to the western coasts of Europe. Fortunately, the Spanish buoy, located northwest of the Iberian Peninsula, was able to measure a set of three successive waves, up to 28 meters high, starting in the area A large locality with a height of 11 meters.

As expected, it is not possible to determine “where and when” these events will occur in a deterministic manner. “However, note the energy of the sea, which is possible with normal forecasts, we are able to provide the probability of its occurrence, that is, the important information for sailors and oil rigs,” continues Benitazzo.

“The danger of these events relates not only to ocean waves, but also to ‘local’ waves. It is good to remember that in normal sea conditions of one meter in height, and in certain circumstances, you can encounter, without warning, isolated individual waves up to They are 2.5 meters high, which are not one-time events, but you can travel with them with a slight adjustment in their height, great distances.” Returning to the case study, “the analysis estimated that the duration of the three-wave beam of 28 meters was about 20 minutes and that it traveled about 20 kilometers. In all these situations, forecasting activity plays an essential role, allowing all seas, including Italian seas, to Noting the significant uptick of the following days and also the likelihood of these apparently anomalies occurring.”

The Commission

spend: Institute of Marine Sciences of Venice Cnr
what: Onorato, M., Cavaleri, L., Randoux, S., Suret, P., Ruiz, M.I., de Alfonso, M., Benetazzo, A., 2021. Ocean, Scientific Reports, 11:23606, 7pp. https://doi.org/10.1038/s41598-021-02875-y

Related