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LONGSHORE CURRENTS AND RIP CURRENTS: MODELIZATION TOWARDS AN OPERATIVE FORECAST

LONGSHORE CURRENTS AND RIP CURRENTS: MODELIZATION TOWARDS AN OPERATIVE FORECAST. Ángel Martínez Ferrer. AEMET (Spanish Meteorological Agency). Madrid amartinezf@aemet.es. EMS Conference, Budapest 3-7 September 2018. CONTENTS:

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LONGSHORE CURRENTS AND RIP CURRENTS: MODELIZATION TOWARDS AN OPERATIVE FORECAST

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  1. LONGSHORE CURRENTS AND RIP CURRENTS:MODELIZATION TOWARDS AN OPERATIVE FORECAST Ángel Martínez Ferrer. AEMET (Spanish Meteorological Agency). Madrid amartinezf@aemet.es EMS Conference, Budapest 3-7 September 2018.

  2. CONTENTS: • LONGSHORE CURRENTS INDUCED BY WAVES: CHANGE OF PARADIGM IN WAVE MODELLING. • WHY FORECASTING LONGSHORE CURRENTS? • WAVE FORECASTING SYSTEM AT AEMET. • RIP CURRENTS. • VERIFICATION OF WAVE AND RIP CURRENTS. • CONCLUSIONS AND FUTURE WORKS. • BIBLIOGRAPHY. Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  3. LONGSHORE CURRENTS INDUCED BY WAVES. WHAT DO LINEAR THEORY OF WAVES SAY ABOUT THE MOTION WITHIN THE WAVES (IN ABSENCE OF OCEANIC CURRENTS)? ORBITAL MOTION OF PARTICLES: ENERGY TRANSPORTATION (AND MOMENTUM; s. Holthuijsen-2007), NO MASS Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  4. BREAKING WAVES, NEAR THE SHORE: MASS AND MOMENTUM TRANSP. Breaking wave >MOMENTUM TRANSPORT  STRESS (…RADIATION STRESS: Sxx, Syy, Sxy) >>HORIZONTAL VARIATIONS IN RADIATION STRESS  FORCES ON THE WATER >>>(STRONG) FORCES AT THE SHORE-SURF ZONE  CURRENTS + SURFACE TILT CHANGE OF PARADIGM IN WAVE MODELLING: THE WAVE ENERGY EQUATION IS NOT ENOUGH TO SOLVE THE MOTION  MOMENTUM EQUATION WITH SHALLOW WATERS TERMS: FRICTION + TURBULENCE (ROLLER) + RAD. STRESS Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  5. WHY FORECASTING LONGSHORE CURRENTS? >>THE SURF AREA AND BREAKING WAVE PARAMETERS: Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  6. WHY FORECASTING LONGSHORE CURRENTS? >>>INITIAL APLICATION: AMPHIBIOUS OPERATIONS Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  7. EARLY INTEREST ON SURF ISSUES: Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  8. EARLY INTEREST ON SURF ISSUES: DEFINITION OF AN INDEX <> TRAFFIC LIGHT CONTRIBUTIONS TO MSI= MSI_HSB + MSI_LongshCurr / MSI_BreakingAngle + MSI_PERIOD + MSI_BreakerKind + MSI_shoreWind Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  9. FORECAST OF BREAKING WAVE PARAMETERS: Breaker angle MSI Hsb, Hmax T Number and type of breakers Breaking area width Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  10. WAVE FORECASTING SYSTEM AT AEMET: MULTIMODEL AND MULTIDOMAIN. >MULTIMODEL: ATMOSPHERE + WAVE + OCEAN + SURF >> WAVES: DEEP WATERS (WAM, WW3) SHALLOW WATERS (SWAN) Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  11. > TELESCOPING NESTED DOMAINS Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  12. RIP CURRENTS. • SOME STATEMENTS ABOUT RIP CURRENTS: • NARROW AND CONCENTRATED SEAWARD FLOWS: FROM THE SHORELINE TO BEYOND THE BREAKERS. • HIGHLY DYNAMIC AND UNSTABLE IN TIME AND SPACE: TEMPORAL CONTROL DEPENDS ON THE WAVE DISSIPATION PATTERNS, SPATIAL CONTROL ON THE BEACH MORPHOLOGY. • THREE CATEGORIES OF RIP CURRENT TYPES BASED ON THE DOMINANT FORCING MECHANISM: HYDRODYNAMICAL-, BATHYMETRICALLY- AND BOUNDARY-CONTROLLED. • SITUATIONS WITH HIGH OCURRENCE OF RIP CURRENTS: SWELL REGIMES, GENTLE SLOPE BATHYMETRY, SANDBARS, ANTHROPOGENIC STRUCTURES, SUBMARINE CANYONS. • BIGGEST HAZARD AT THE BEACH, PRODUCING MOST DROWNINGS AND RESCUES. Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  13. CURRENTS AT THE BEACH TESTED WITH XBEACH (BY DELTARES, THE NETHERLANDS): Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  14. SIMULATING WITH XBEACH: • surfbeat mode, • 2D hydrostatic, • 48h range, 10 m res, domain 5600 x 3000m: 170,000 nodes 1.5 h running LONGSHORE COMPONENT: CURRENT: CROSSHORE COMPONENT: Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  15. VERIFICATION OF WAVE FORECASTS: Easterlies in the Strait: Correlation buoy-model. Forcing winds from Hirlam 5 km and Harmonie 2.5 km Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  16. VERIFICATION OF RIP CURRENT FORECASTS? LAGRANGIAN OR EULERIAN? Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  17. CONCLUSIONS AND FUTURE WORKS: • AN OPERATIONAL PREDICTION TOOL IS BEING IMPLEMENTED IN AEMET TO FORECAST CURRENTS ALONG THE SHORE. IT REPRESENTS THE FINAL STEP OF THE WAVE FORECASTING SYSTEM. • THE XBEACH MODEL IS ABLE TO PREDICT ALONGSHORE CURRENTS. RIP CURRENT FORECAST NEEDS ADDITIONAL CONSIDERATIONS AND A REAL CALIBRATION. • CALIBRATION OF THE MODEL AND VERIFICATION OF RESULTS ARE KEY ASPECTS TO FINALLY LEAVE THOSE FORECASTS AT PUBLIC’S DISPOSAL. VISUAL, QUALITATIVE VERIFICATIONS MAY BE THE BEST FEASIBLE SOURCE. • DOMAINS OF STUDY NEED TO BE OPTIMIZED IN TERMS OF COMPUTATIONAL COST TO ENSURE AVAILABILITY AND ACCURACY OF PREDICTIONS. • INFLUENCE OF COMPLEX PHENOMENA (MORPHOLOGY, LONG WAVES) SHOULD BE EVALUATED TO DECIDE IF INCLUDE THEM OR NOT IN THE SIMULATION. Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

  18. BIBLIOGRAPHY: • - Holthuijsen, L.H. 2010. Waves in Oceanic and Coastal Waters, Cambridge University Press, 387 pp. • - Mettlach, T.R. et al. 2002. Software Design for the Navy Standard Surf Model Version 3.2, NRL, 189 pp. • - Roelvink, D. et al. 2009. Modelling storm impact on beaches, dunes and barrier islands, Coastal Engineering, Elsevier, doi: 10.2016/j.coastaleng.2009. 08.006 • - Comet modules: https://www.meted.ucar.edu/marine • Longuet-Higgins, M. S. and R. W. Stewart,1962, Radiation stress and mass transport in gravity waves, with applications to “surf beats”, J. Fluid Mech., 13, 481–504 • Martin J. Austin, Tim M. Scott, Paul E. Russell, and Gerd Masselink (2013) Rip Current Prediction: Development, Validation, and Evaluation of an Operational Tool. Journal of Coastal Research: Volume 29, Issue 2: pp. 283 – 300. Longshore currents and rip currents. EMS Conference, Budapest 3-7 September 2018.

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