Influence of wave-current interaction, and high frequency forcing upon storm induced currents and elevations

A high resolution (of order 1 km grid) three dimensional model of the Easte rn Irish Sea, including wave-current interaction effects, is used to examin e the surges of November 1977. Computed surge elevations and currents are c ompared with observations taken at the time. The inclusion of wave-current interaction effects, in which the amplitude of the surface wind-wave field changes over the period of the storm, is shown to influence computed surge elevations in shallow regions. The inclusion of wave-current interaction ef fects also influences currents, particularly in the near bed region. An inc rease in air-sea drag coefficient, reflecting an enhanced sea surface rough ness due to increased wave heights at the time of the storm, is shown to im prove the computed storm surge elevation in shallow regions. The effects of including a high frequency component (based on observations) into the lower frequency meteorological forcing usually used to drive the model, is examined. Such fluctuations produce high frequency variations in the near surface currents, however such changes are not found at depth. The introduction of similar high frequency changes into the currents along the open boundary of the model is also considered. This produces high frequenc y variations throughout the water column, within the interior of the Easter n Irish Sea, which are similar to those found in the observations.