Surfzone-inner Shelf Interaction Analyzed with an Eulerian-averaged Primiteve Equation Based on Vortex-force Formalism

Abstract

Recent observational studies have rediscovered that littoral currents are inevitable for interaction between surfzone and inner shelf (e.g., Lentz et al., 2008). A synoptic, detailed numerical experiment is conducted to pursue this problem with a multi-nested coupling system consisting of ROMS-WEC (Uchiyama et al., 2010), SWAN and WRF at horizontal resolutions down to 20 m. Both the Eulerian and Lagrangian analysis clearly demonstrate that wave-driven three-dimensional currents significantly enhance lateral and vertical mixing and dispersion. Lagrangian particle tracking and two-particle analysis exhibit that rip and undertow induce vertical secondary flow that plunges those particles downwards beyond the pycnocline, leading to markedly increased initial dilution and thus much faster relative dispersion tendency.