Day 4

Detailed paper information

Back to list

Paper title Spatial assessment of wind-wave coupling in the western Gulf of Mexico
Authors
  1. Guillermo Díaz Méndez CIGoM - CICESE Speaker
  2. Francisco Javier Ocampo-Torres CEMIE-Oceano AC-CICESE
  3. J. Pedro Osuna CICESE
  4. Nicolas Rascle CICESE
  5. Bernardo Esquivel-Trava CICESE
  6. Rogelio Hasimoto-Beltrán Center for Research in Mathematics-CIMAT
  7. Mario Canul-Ku Center for research in Mathematics-CIMAT
Form of presentation Poster
Topics
  • A8. Ocean
    • A8.14 Remote-sensing of Ocean Waves and their Applications
Abstract text Inspired on the work of Cavaleri et al. [2012], where the concept of the so-called swell-wind (i.e., a "low-level wave-driven wind jet" as described in 2010 by Hanley et al.) is discussed, this work-in-progress aims to investigate the spatial variability of wind-wave coupling in a semi-enclosed basin through the analysis of SAR imagery. A global climatology and seasonal variability of wind-wave coupling was computed by the latter authors through the inverse wave age parameter, derived from numerical results of the ERA-40 dataset. They identified areas where, and times when, wind-driven wave conditions (U_10 cosθ / c_p > 0.83) and wave-driven wind regimes (U_10 cosθ / c_p < 0.15) occur, the latter coinciding with the swell pools found by Chen et al. [2002]. They also found that in enclosed seas, where wave-growth (and hence, c_p) is limited by fetch, the wind-driven wave regime is most common, as proposed by Drennan et al. [2003].

In this work, maps of inverse wave age have been computed from wind and wave information derived from Sentinel-1 and TerraSAR-X images acquired over the Gulf of Mexico and validated with buoy observations. Mean wave conditions at the Gulf of Mexico are mild (Hs < 2 m) and mostly driven by the Trade Winds, so that its propagation direction has a strong zonal component and is somewhat normal to these platform's flight direction. This allows for a reliable SAR detection. Under such conditions, inverse wave age lies in the "mixed" regime (0.15 < U_10 cosθ / c_p < 0.83) and its spatial variability appears to be induced mostly by the wind's. However, when the sea surface is forced by the high-wind conditions associated with atmospheric cold surges (November through May) and tropical cyclones (June through November), waves can be as high as 7 m and reach peak period values above 13.5 s, as recorded by NDBC stations 42002 and 42055 in 2020. Spatial variability of the inverse wave age parameter seems then to be dependent mostly on the phase speed and propagation direction of the waves, specially in cases where shorter- and longer-wavelength systems coexist. During these extreme conditions, both wind-driven seas and wave-driven winds have been estimated, indicating areas where the ocean yields momentum into the atmosphere. This study supports the hypothesis that momentum flux can be highly variable (i.e., spatially inhomogeneous) not only near the coast but in the open ocean, as proposed by Laxague et al. [2018].