SAR Observation of Rip Currents off the Portuguese Coast

  • J. C. B. da Silva

Signatures of rip currents can be identified in SAR images and aerial photographs of the near-shore. An area on the Portuguese West coast (bathymetry and wave climate of which are briefly described) was studied. An image corresponding to low wind speed conditions is shown, where a series of rip-like cell features are consistent with rip current morphology. A simple model is presented to explain the signatures, based on wind contrast due to the relative water motion within rip currents. The model is discussed for near-threshold wind conditions of Bragg wave excitation.


Internal Wave Synthetic Aperture Radar Significant Wave Height Wave Breaking Synthetic Aperture Radar Image 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Aagaard T, Masselink G (1999) The surf zone, In: Short AD (ed), Handbook of Beach and Shoreface Morphodynamics, John Wiley & Sons, Chichester, Chapter 4, pp 72-118Google Scholar
  2. Amorocho J, De Vries JJ (1980) A new evaluation of the wind stress coefficient over water surface. Journal of Geophysical Research 85: 433-442CrossRefGoogle Scholar
  3. Belcher SE, Hunt JCR (1998) Turbulent flow over hills and waves. Annu. Rev. Fluid Mech. 30: 507-538CrossRefGoogle Scholar
  4. Da Silva JCB, Ermakov SA, Robinson IS (2000) Role of surface films in ERS SAR signatures of internal waves on the shelf, 3. Mode Transitions. Journal of Geophysical Research 105: 24089-24104CrossRefGoogle Scholar
  5. Da Silva JCB, Sancho F, Quaresma L (2006) Observation of Rip Currents by Synthetic Aperture Radar. Proceedings of SEASAR 2006, Advances in SAR Oceanography from ENVISAT and ERS missions, ESA publication SP-613, Frascati, ItalyGoogle Scholar
  6. Ermakov SA, da Silva JCB, Robinson IS (1998) Role of surface films in ERS SAR signatures of internal waves on the shelf. 2. Internal (tidal) waves. Journal of Geophysical Research 103: 8032-8043CrossRefGoogle Scholar
  7. Gomes F, Bessa Pacheco M, Jorge da Silva A, Silva R, Rusu E (2005) A Utilização dos SIG na estimativa da corrente de deriva litoral (Aplicação à costa oeste de Portugal continental entre a Figueira da Foz e a Nazaré), Instituto Hidrográfico, internal manuscript with pp 9 in PortugueseGoogle Scholar
  8. Hasselmann K (1968) Weak-interaction theory of ocean waves. In: Holt M (ed) Basic Developments in Fluid Dynamics, vol 2. Academic Press, San Diego, pp 117-182Google Scholar
  9. Holt B (2004) SAR imaging of the ocean surface, Chapter 2. In: Jackson C, Apel J (ed) Synthetic Aperture Radar Marine User´s Manual. U.S. Department of Commerce and NOAA, Washington DC, pp 25-79Google Scholar
  10. Hughes BA (1978) The effect of internal waves on surface wind waves, 2. Theoretical Analysis. Journal of Geophysical Research 83: 455-465CrossRefGoogle Scholar
  11. Keller WC, Wright JW (1975) Microwave scattering and the straining of wind-generated waves. Radio Science 10: 139-147CrossRefGoogle Scholar
  12. MacMahan JH, Thornton EB, Reniers AJHM (2006) Rip current review. Coastal Engineering 53: 191-208CrossRefGoogle Scholar
  13. Oliveira F, Oliveira T, Silva R, Larangeiro S (2004) Dinâmica sedimentar do trecho litoral Praia da Vieira - Praia Velha. VII Congresso da Água, Lisboa, Portugal, cd-rom. pp 15-30, in PortugueseGoogle Scholar
  14. Short AD (1985) Rip current type, spacing and persistence, Narrabeen Beach, Australia. Marine Geology 65: 47-71CrossRefGoogle Scholar
  15. Short AD, Hogan CL (1994) Rip currents and beach hazards, their impact on public safety and implications for coastal management. In: Finkl CW (ed) Coastal Hazards, Journal of Coastal Research, Special Issue 12. pp 197-209Google Scholar
  16. Silva FS (2006) Rip Currents Identification with Synthetic Aperture Radar. Lic. Dissertation Thesis, Faculdade de Ciências do Mar e do Ambiente, University of Algarve, Faro. pp 73, in PortugueseGoogle Scholar
  17. Yu J, Slinn DN (2003) Effects of wave-current interaction on rip currents. Journal of Geophysical Research 108: 3088 doi:10.1029/2001JC001105CrossRefGoogle Scholar
  18. Smith JM (1999) Wave breaking on an opposing current. Coastal Engineering Technical Note CETN IV-17. U.S. Army Engineer Research and Development Center, Vicksburg, MS, pp 9Google Scholar
  19. Wackerman CC, Clemente-Colón P (2004) Wave Refraction, Breaking and Other Near-Shore Processes. In: Jackson C, Apel J (ed) Synthetic Aperture Radar Marine User’s Manual. U.S. Department of Commerce and NOAA, Washington DC, pp 171-187Google Scholar
  20. Willebrand J (1975) Energy transport in a non-linear and inhomogeneous random gravity wave field. Journal of Fluid Mechanics 70: 113-126CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V 2008

Authors and Affiliations

  • J. C. B. da Silva
    • 1
  1. 1.Institute of OceanographyUniversity of LisbonPortugal

Personalised recommendations