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Effects of gap-winds on multi-modal ocean Swell systems at the south Pacific coast of Mexico

Guillermo Díaz-Méndez(1), Francisco J. Ocampo-Torres(2), Pedro Osuna-Cañedo(2), Héctor García-Nava(2) and Reginaldo Durazo-Arvizu(1)

(1) Universidad Autonoma de Baja California, Km 106 carretera Tijuana-Ensenada, 22880 Ensenada, BC, Mexico
(2) CICESE, Km 107 carretera Tijuana-Ensenada, 22880 Ensenada, BC, Mexico


Along with the Gulfs of Papagayo and Fonseca located on Central America, the Gulf of Tehuantepec, located at the South Pacific coast of Mexico, is characterized by the occurrence of strong gap-winds blowing off-shore into the Pacific Ocean during the winter months (Chelton et al., 2000; Romero-Centeno et al., 2003 and 2007). South blowing gap-winds present at Tehuantepec are locally known as Tehuano winds; events have a persistence of up to 4 days each, often reaching sustained velocities above 17 m/s and blow as far south as latitude 10° N. Tehuano events induce strong surface currents up to 1.5 m/s (R. Durazo, pers. comm.) as well as fetch limited wind-sea propagating to the South (García, 2006). Strong Tehuano events are believed to induce variability on the evolution of the ocean swell 2D spectrum: wave refraction by currents, broadening of the directional spreading and transfer of energy by the wind, particularly for smaller wave numbers.

With the objective of studying the effects of Tehuano winds on the ocean swell a series of ENVISAT (A)SAR SLC images have been analyzed. Wave inversions have revealed multi-modal spectra with up to three swell peaks propagating into the vicinity of the Gulf of Tehuantepec from different sites on the Pacific and Indian Ocean. Wavelength of these peaks are in the range of 200 to 300 m and wave heights reach up to 3 m. Main peak directions are approximately aligned with the satellite azimuth direction while secondary and tertiary peaks are 20 to 120 degrees to the right of the main direction. These results agree fairly well with in-situ wave records, which have been used as well to backtrack wave spectra towards their originating storms following Snodgrass et al. (1966).

Blockage and non-linear interaction of these systems is currently under investigation.


Workshop presentation

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry