Deep-water spectral wave steepness offshore mainland Portugal
Deep-water spectral wave steepness (sm) is used in several ocean engineering activities to characterise sea states. However, difficulties in maintaining wave buoys offshore the continental shelf results in a lack of deep-water sm variability studies based on long-term field observations in high-energetic environments. In this work, we analysed sm variability between 1200 and 1900 m water depth offshore mainland Portugal (North Atlantic Ocean) based on field measurements recorded between 2009 and 2020 at three different locations. Results show similar sm variability at the three sites with mean, minimum and maximum values of 0.031, 0.004 and 0.072, respectively. A decrease in the monthly average sm to 0.027 is observed for all locations during September and October. Values of sm displayed a decreasing tendency with a rotation of the mean wave direction towards the North. Under storm conditions, sm ranged between 0.020 and 0.060 and no correlation was found between sm and other wave parameters, such as significant wave height, mean wave period or mean wave direction. For the most severe storms, values of sm were in general larger than 0.030, which points out that storm waves display larger sm.
Diogo Mendes, Tiago C.A. Oliveira(2021), “Deep-water spectral wave steepness offshore mainland Portugal”, Ocean Engineering, Volume 236, 2021, 109548, ISSN 0029-8018