Waves along Eastern boundary currents – The regional winds effect

Abstract

The wind fields along the five eastern boundary currents (EBC) systems (California, Canary, Humboldt, Benguela, and West Australia) are highly seasonal. This seasonality is mostly determined by the position of the semi-permanent high pressure cells over the ocean. During summer these high pressure cells, with a thermal low pressure systems inland, are the synoptic drivers of along coast winds. These strong summer winds, along the EBC systems, off-shore mid-latitude continental coasts, generate waves that can be rather extreme, considering that these areas can be seen as limited fetch wave fields. A qualitative analysis of the wave climate over the mid-latitudes western coastal areas, along the five EBC systems, based on the ERA-Interim reanalysis wave data, is presented. The influence of coastal wind speed intensification processes in these areas, like the occurrence of coastal low-level jets, and expansion fans in the lee of headlands and capes, on the local wave field is studied. It is shown that, despite the distance between the five EBC systems, their wave fields, particularly during summer, are very similar when the wind sea and swell characteristics are balanced. In summer locally generated wave heights and energy content, along EBC areas, are comparable or even higher than swell ones.