A study of the wave effects on the current circulation in Galway Bay, using the numerical model COAWST

TL;DR

This study uses the COAWST model to analyze wave-current interactions in Galway Bay, finding limited overall impact of wave coupling but significant local effects during storms, especially on surge and currents.

Contribution

It provides a detailed analysis of wave effects on circulation in Galway Bay, highlighting the roles of wave-induced surge and surface roughness during storm conditions.

Findings

Wave coupling marginally improves model accuracy overall.

Storms cause significant wave-induced surge and current responses.

Surface roughness changes are key to current variations during storms.

Abstract

A model coupling waves and currents is set up for Galway Bay, Ireland, using COAWST. The impact of the coupling on the accuracy of the model is shown to be marginal on the overall statistics. The model is in good agreement with the available in-situ observations that are used for the validation. However a closer look at the data during storms shows a deterioration of the agreement, which is barely improved by the coupling. A special analysis of the different processes ruling the ocean circulation and wave propagation is conducted during Storm Hector (2018/06/14). It shows a strong wave-induced surge by 7cm in the back of Galway Bay, and a strong response in terms of currents along the coast of Clare of about 30cm/s. Most of the surge is attributed to the impact of the conservative wave-induced forcing terms, but the main process involved is not identified. The response in currents is partly attributed to the conservative wave-induced forcing terms, but mostly to the wave-enhanced surface roughness.