Observations of Surface Wave–Current Interaction

Abstract

Wave–current interaction can result in significant inhomogeneities of the ocean surface wave field, including modulation of the spectrum, wave breaking rates, and wave statistics. This study presents novel airborne observations from two experiments: 1) the High-Resolution Air–Sea Interaction (HiRes) experiment, with measurements across an upwelling jet off the coast of Northern California, and 2) an experiment in the Gulf of Mexico with measurements of waves interacting with the Loop Current and associated eddies. The significant wave height and slope varies by up to 30% because of these interactions at both sites, whereas whitecap coverage varies by more than an order of magnitude. Whitecap coverage is well correlated with spectral moments, negatively correlated with the directional spreading, and positively correlated with the saturation. Surface wave statistics measured in the Gulf of Mexico, including wave crest heights and lengths of crests per unit surface area, show good agreement with second-order nonlinear approximations, except over a focal area. Similarly, distributions of wave heights are generally bounded by the generalized Boccotti distribution, except at focal regions where the wave height distribution reaches the Rayleigh distribution with a maximum wave height of 2.55 times the significant wave height, which is much larger than the standard classification for extreme waves. However, theoretical distributions of spatial statistics that account for second-order nonlinearities approximately bound the observed statistics of extreme wave elevations. The results are discussed in the context of improved models of breaking and related air–sea fluxes.

Distribution of Surface Wave Breaking Fronts

“…Wave breaking variability due to wave‐current interactions was investigated with currents measured by HF radar. The results are qualitatively consistent with the measurements by Romero et al (), but the measurements exhibit substantially more variability at small scales, likely due to statistical sampling and submesoscale current variability not resolved by the HF radar.…”

“…The model solutions shown with thick lines where forced with homogeneous winds as opposed to those forced with relative winds (RW) shown with thick lines. For reference, see Λ( c ) sampling flight tracks in Romero et al (, Figure 7e).…”

Simulation of Wave‐Current Interactions Under Hurricane Conditions Using an Unstructured‐Grid Model: Impacts on Ocean Waves

“…The coupled model results were evaluated (Chen et al, ) by observations of surface waves and winds during hurricane Frances (2004). The observations of wave‐current interactions were collected by measuring winds, water levels, waves, and currents (Fewings et al, ; Hopkins et al, ; Lentz et al, ; Romero et al, ). Hopkins et al () concluded that the modulation of wave directions in shallow (2 and 7 m) water depths could reach 70° owing to the current‐induced refraction, based on a month of observations of wave directions and mean currents.…”

Hazard Assessment of Typhoon-Driven Storm Waves in the Nearshore Waters of Taiwan

“…Refractions are triggered when waves propagate over spatially varying and strong currents [17,18]. Additionally, wave steepening can arise if the current direction is in contrast to the wave's direction [19]. The effect that tide and surge have on the wave must also be considered in numerical models, since the incident wave height increases during rising tides in the coastal zone [20].…”