Abstract
Operational ocean and wave models are used to produce forecasts for
navigation but also required for a wide range of services, most of them
relying on particle tracking methods. Improving the forecast
capabilities and accuracy of a model is then a constant necessity in
order to deliver more reliable services. The Marine Institute in Ireland
is running several coastal operational models, one of them focuses on
the area of Galway Bay in the west coast. At the moment it consists of a
stand-alone ocean application, it is the purpose of the work presented
here to set-up a coupled application with a wave model. Coupled models
are a recent development in ocean modelling, developer teams have
included ocean and wave coupling by combining existing models each
dedicated to a specific physics. Two theoretical formulations are mostly
used for the implementation, both giving the same equations of evolution
and interaction terms known as the vortex-force formalism. One approach
is using a Lagrangian framework defining an exact averaged operator
following the fluid particles, the other approach is Eulerian making use
of a multi-scale expansion. In both cases the larger current components
are found to be forced by gravity and infra-gravity waves. The Coupled
Ocean Atmosphere Wave Sediment Transport (COAWST) modelling system is a
widely used code, the vortex-force formalism has been implemented in
2012 coupling the Regional Ocean Modeling System (ROMS) with the
Simulation Wave Nearshore wave model (SWAN). The implementation has been
validated with academic cases and used in several real case studies in
the last decade. The work presented here is making use of COAWST, a
coupled model is set-up for Galway Bay running a 1-year hind-cast
application for 2017 and preliminary results are shown here. The
performance of the coupled model is compared with each stand-alone
model, using in-situ data as a reference. In the last releases of COAWST
the wave model WAVEWATCHIII has been added and can be used in the
coupled system. This new feature is tested and the results are compared
against SWAN, both wave codes are solving the same equations but
different technical choices have been made resulting in different
capabilities.