A worldwide coastal analysis of the wave systems

<p>Wave climate is usually characterized with the bulk parameters (Significant Wave Height, Peak Period, Mean Wave Direction). Local wind generated waves are however the result of the wave energy through a frequency-direction wave spectrum. One of the most common problems encountered using the bulk parameters is the loss of information concerning different wave systems. The ocean surface is a combination of waves coupled to the local wind (wind sea) or generated elsewhere (swells). The aim of this study is to analyze the coastal climate conditions of the wave systems. Wave directional 3-hourly spectral data from the 30yrs 1989-2020 historical time period at about 10.000 locations worldwide are used.</p> <p>The methodology to obtain spectral partitions from the directional wave spectrum was initially proposed by Hanson and Jensen (2004) and based on the watershed algorithm (Vincent and Soille, 1991). Once the partitions are obtained, wind and swell/s are obtained.. Wind seas are identified using a wave age criterion, such that wind sea peaks lie within parabolic boundaries. Any partition whose peak falls within the wind sea region is considered to be forced by the wind and initially defined as wind sea. All wind seas partitions from a given input spectrum are combined. The swell wave systems are obtained from the aggregation of all the swell partitions, during the whole time, coming from the same direction, obtaining then a mean wave climate probability spectrum. This spectrum is further partitioned using the watershed algorithm.</p> <p>Once the swell wave systems are obtained, the corresponding energy (m0) allows to estimate the dominance of the swells and the wind sea. In some areas the wind sea has higher energy than the swells (e.g. Gulf of Carpentaria, Baltic Sea), while other areas are dominated by a strong swell (e.g. south Atlantic European coast), or the coexistence of multiple swells (e.g. Pacific Islands). In general, for enclosed seas, wind sea and swell are concurrent. Overall, on the East coast of the continents the swells coexist with wind sea, whereas on the West coast the swells prevail.</p>