Authors: Francesco Fedele, Joseph Brennan, Sonia…
Freak Waves, an exceptional phenomenon
Public Lecture by Peter Janssen on the 3rd of June 2014.
Although freak wave events are rare, they do happen and may cause considerable damage. However, in the past, mainly due to lack of empirical evidence or because, when there was evidence, it was not believed, the freak wave phenomenon has not been given much attention. This picture gradually changed when in the early 1990's numerical simulations showed the generation of extreme ocean waves caused by four-wave interactions, while in the mid 1990's the first sound empirical evidence on freak waves was presented.
I am involved in the subject of operational wave forecasting, which means that for all oceans we forecast the average sea state with a spatial resolution of about 25 km. A theoretical framework has been developed that allows to estimate how large the deviations from the average sea state can be. These deviations then provide information on how large individual waves can become, and therefore operationally information on the likelihood of extreme events can be provided nowadays.
The generation of freak waves by four-wave interactions has triggered a lot of scientific interest. In the narrow-band approximation the dynamics of the waves is determined by the nonlinear Schroedinger equation, an equation which is found in many other branches of physics, e.g. in nonlinear optics, plasma physics and in meteorology. Thus, although ocean freak waves are rare in nature, they are a fairly common phenomenon in labs all over the world since nowadays there is a better understanding of their generation.
Peter Janssen has worked in the field of theory and modelling of ocean waves
since 1979. He took as Chairman of the WAM Development and Implementation
group an active part in the development of the third generation WAM model.
He was one of the first to assimilate Altimeter wave heights
into a global ocean wave prediction system. He is since January 1995 head of
ECMWF's ocean wave modelling group and as such is also responsible for
the quality of the surface winds over the global oceans. In particular he
introduced in 1998 the first operational coupled ocean-wave, atmosphere
model, which is still in use for operational weather forecasting and seasonal
forecasting at ECMWF. Recently, he has developed an operational freak wave
warning system. In 2011 he became head of the Marine Prediction Section to work
on the development of a coupled atmosphere, ocean-wave, ocean/sea-ice system
for analysis and for medium-range and seasonal prediction.
The public lecture will take place as part of the 3rd MULTIWAVE Workshop in the Moore Auditorium (Earth Science Institute, UCD) on the 3rd of June 2014 at 6pm.
For more information please see http://earth.ucd.ie/event/public-lecture-freak-waves-an-exceptional-phenomenon/
Please register at https://freakwaves.eventbrite.ie (free event)