The impact of ocean-wave coupling on the upper ocean circulation during
storm events
Abstract
Many human activities rely on accurate knowledge of the sea surface
dynamics. This is especially true during storm events, when wave-current
interactions might represent a leading order process of the upper ocean.
In this study, we assess and analyse the impact of including three
wave-dependent processes in the ocean momentum equation of the Met
Office North West European Shelf (NWS) ocean-wave forecasting system on
the accuracy of the simulated surface circulation. The analysis is
conducted using ocean currents and Stokes drift data produced by
different implementations of the coupled forecasting systems to simulate
the trajectories of surface (iSphere) and 15 m drogued (SVP) drifters
affected by four storms selected from winter 2016. Ocean and wave
simulations differ only in the degree of coupling and the skills of the
Lagrangian simulations are evaluated by comparing model results against
the observed drifter tracks. Results show that, during extreme events,
ocean-wave coupling improves the accuracy of the surface dynamics by
4%. Improvements are larger for ocean currents on the shelf (8%) than
in the open ocean (4%): this is thought to be due to the synergy
between strong tidal currents and more mature decaying waves. We found
that the Coriolis-Stokes forcing is the dominant wave-current
interaction for both type of drifters; for iSpheres the secondary wave
effect is the wave-modulated water-side stress while for SVPs the
wave-dependent sea surface roughness is more important. Our results
indicate that coupled ocean-wave systems may play a key role for
improving the accuracy of particle transport simulations.