Stokes Drift Effects Computed From Measured Wave Data

Abstract

The effect of mean mass transport on the surface of the sea due to wave movement and known as “Stokes Drift” plays an important role in forecasting the movement of floating pollutants and is also of paramount importance when evaluating the boundary conditions for the computation of coastal circulation; this paper presents an attempt to supplement the usual approach based on monochromatic waves or standard spectral simulations with an analysis of measured time series of waves.

Wave heights and periods are computed from records of water height data obtained with a Datawell wave gauge located in the Bay of Naples in different sea states through the usual zero-upcrossing procedure, and wave parameters are estimated; once such parameters are known and a wave theory is assumed the computation of the drift velocity is quite straightforward.

These computations yield a mean drift velocity for all available sea records, which include both calm and very rough sea conditions; correlations are found to relate drift to the sea state.