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Coastal trapped waves along the portuguese coast
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Abstract(s)
Atmospheric forcing near a coastline can lead to the formation of coastal trapped waves. These waves can travel significant longshore distances at high speeds and induce coastal processes such as upwelling.
Coastal trapped waves have been observed around the globe, however they remain an almost unstudied phenomenon near the Portuguese coast.
In the present study sea level, atmospheric pressure, wind and sea surface temperature data from along the Portuguese coast are used in order to attempt to detect the occurrence of coastal trapped waves. The data records are analysed through use of the cross-correlation and spectral analysis methods.
Coastal trapped waves have been detected along the Portuguese coast. Evidence was found for the first three coastal trapped modes, which were observed to propagate along the coast with speeds between 2-3 ms-1 for the first mode, between 1.2-1.8 ms-1 for the second mode and around 0.75 ms-1 for the third mode. The sea level spectra also contained peaks at frequencies corresponding to the second and third mode.
The observed coastal trapped waves did not seem to reach Cascais. This is likely to be due to the geomorphologic characteristics of the continental shelf between Setúbal and Cascais.
The forcing mechanism behind the coastal trapped waves was found to be the variations in the longshore wind. Generally, a delay of 12 hours exists between the wind forcing and the coastal trapped wave propagation.
The wind forcing was also found to induce local upwelling, however no evidence was found for the occurrence of upwelling induced by the passage of coastal trapped waves.
Description
Tese mest. , Oceanografia, 2008, Universidade do Algarve
Keywords
Teses Ondas Costa litoral Afloramento costeiro 551.46