LONGSHORE CURRENTS AND RIP CURRENTS MODELIZATION TOWARDS AN

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: - 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. 2

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. 3

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. 4

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

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

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

EARLY INTEREST ON SURF ISSUES: DEFINITION OF AN INDEX <> TRAFFIC LIGHT CONTRIBUTIONS TO MSI= MSI_HSB + MSI_Longsh. Curr / MSI_Breaking. Angle + MSI_PERIOD + MSI_Breaker. Kind + MSI_shore. Wind Longshore currents and rip currents. EMS Conference, Budapest 3 -7 September 2018. 8

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. 9

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

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

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 BOUNDARYCONTROLLED. - 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. 12

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

SIMULATING WITH XBEACH: - surfbeat mode, - 2 D hydrostatic, - 48 h range, 10 m res, domain 5600 x 3000 m: 170, 000 nodes 1. 5 h running CURRENT: LONGSHORE COMPONENT: CROSSHORE COMPONENT: Longshore currents and rip currents. EMS Conference, Budapest 3 -7 September 2018. 14

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. 15

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

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. 17

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. 18