Sun glitter imagery of surface waves. Part 2: Waves transformation on ocean currents

Under favorable imaging conditions, the Sentinel-2 Multi-Spectral Instrument (MSI) can provide spectacular and novel quantitative ocean surface wave directional measurements in satellite Sun Glitter Imagery (SSGI). Owing to a relatively large-swath with high-spatial resolution (10 m), ocean surface roughness mapping capabilities, changes in ocean wave energy, and propagation direction can be precisely quantified at very high resolution, across spatial distances of 10 km and more. This provides unique opportunities to study ocean wave refraction induced by spatial varying surface currents. As expected and demonstrated over the Grand Agulhas current area, the mesoscale variability of near-surface currents, documented and reconstructed from satellite altimetry, can significantly deflect in-coming south-western swell systems. Based on ray-tracing calculations, and unambiguously revealed from the analysis of Sentinel-2 MSI SSGI measurements, the variability of the near-surface current explains significant wave-current refraction, leading to wavetrapping phenomenon and strong local enhancement of the total wave energy. In addition to its importance for wave modeling and hazard prediction, these results open new possibilities to combine different satellite measurements and greatly improve the determination of the upper ocean mesoscale vorticity motions.

[1]  Bertrand Chapron,et al.  Direct measurements of ocean surface velocity from space: Interpretation and validation , 2005 .

[2]  Bertrand Chapron,et al.  Space-time structure of long ocean swell fields , 2009, 0910.1496.

[3]  John W. Miles,et al.  The Dynamics of the Upper Ocean, 2nd Edition. By 0. M. PHILLIPS. Cambridge University Press, 1977. 336 pp. $16.00 or $34.00. , 1978, Journal of Fluid Mechanics.

[4]  A. N. Bol’shakov,et al.  Observations of wind waves in the Gulf Stream frontal zone , 1995 .

[5]  V. Kudryavtsev,et al.  Slippery Near-Surface Layer of the Ocean Arising Due to Daytime Solar Heating , 1990 .

[6]  Walter Munk,et al.  Directional recording of swell from distant storms , 2013, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[7]  W. Mcleish,et al.  Wave refraction in an ocean front , 1985 .

[8]  A. M. Walker.  Statistical Analysis of a Random, Moving Surface , 1957, Nature.

[9]  R. Raney,et al.  Theory of synthetic aperture radar ocean imaging: A MARSEN view , 1985 .

[10]  T. Barnett,et al.  Estimation of the two‐dimensional ocean current shear field with a synthetic aperture radar , 1989 .

[11]  J. Johannessen,et al.  On radar imaging of current features: 1. Model and comparison with observations , 2005 .

[12]  Donald R. Thompson,et al.  The influence of the marine atmospheric boundary layer on ERS 1 synthetic aperture radar imagery of the Gulf Stream , 1997 .

[13]  J. Johannessen,et al.  Mapping the Agulhas Current from space: An assessment of ASAR surface current velocities , 2010 .

[14]  W. Munk,et al.  Propagation of ocean swell across the Pacific , 1966, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[15]  Kern E. Kenyon,et al.  Wave refraction in ocean currents , 1971 .

[16]  Bertrand Chapron,et al.  ASAR imaging for coastal upwelling in the Baltic Sea , 2012 .

[17]  Bertrand Chapron,et al.  Wave and wind retrieval from sar images of the ocean , 2001, Ann. des Télécommunications.

[18]  D. E. Irvine,et al.  Ocean wave directional spectra and wave‐current interaction in the Agulhas from the Shuttle Imaging Radar‐B synthetic aperture radar , 1988 .

[19]  George R. Mapp,et al.  Wave refraction by warm core rings , 1985 .

[20]  J. Johannessen,et al.  Imaging mesoscale upper ocean dynamics using synthetic aperture radar and optical data , 2012 .

[21]  R. Shuchman,et al.  SEASAT synthetic aperture radar observations of wave‐current and wave‐topographic interactions , 1983 .

[22]  Antony K. Liu,et al.  Wave‐current interaction study in the Gulf of Alaska for detection of eddies by synthetic aperture radar , 1994 .

[23]  B. Chapron,et al.  Monitoring and analysis of ocean swell fields from space: New methods for routine observations , 2009 .

[24]  V. Kudryavtsev,et al.  Observations of atmospheric boundary layer evolution above the Gulf Stream frontal zone , 1996 .

[25]  Werner Alpers,et al.  WHY SAR WAVE MODE DATA OF ERS AND ENVISAT ARE INADEQUATE FOR GIVING THE PROBABILITY OF OCCURRENCE OF FREAK WAVES , 2006 .

[26]  I. Robinson,et al.  Sensitivity of the diurnal warm layer to meteorological fluctuations part 1: observations , 2005 .

[27]  Bertrand Chapron,et al.  Surface Roughness Imaging of Currents Shows Divergence and Strain in the Wind Direction , 2014 .

[28]  Basile Gallet,et al.  Refraction of swell by surface currents , 2014, 1410.1676.

[29]  Bertrand Chapron,et al.  Observation of swell dissipation across oceans , 2008, 0809.2497.

[30]  M. Longuet-Higgins.  The statistical analysis of a random, moving surface , 1957, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.