Extreme waves in visual wave observations by VOS

Being a disastrous phenomenon, extreme waves (including those classified as rouge waves) are critically important for marine structures. Although there are many works on the theory of rogue waves [e.g. 1, 2, 3, 10, 11, 12, 13], their physics of is still poorly understood and they are hardly detectable in different wind wave data. Furthermore, we have very tentative estimates of rogue waves and in most wave data it is hard to discriminate between the observational truth and the measurement artifacts of different nature when very high waves are in question. In this paper we will analyse the collection of visual observations worldwide in order to quantify the most extreme wave cases and to identify their nature. Besides model hindcasts, satellite and buoy measurements Voluntary Observing Ship (VOS) data represent now an important source of global wave information, including that of extreme wave events. There is a general concern that VOS observations are quite inaccurate and, therefore, are hardly applicable for quantitative wind wave analysis. However this concern results primarily from a poor knowledge of the actual errors and uncertainties inherent in the VOS wave observations. This accuracy was more or less quantified during the last years and many errors and uncertainties were either minimized or removed from the VOS collection [5]