Southern african wave model sensitivities and accuracies

Abstract

Numerous studies have identified the complexities of the wave climatology around the South African coast, but limited studies have investigated these complex dynamics in the available literature. Several freely available parameterized wave boundary conditions are produced around southern Africa. However, none of these are fully spectral outputs from global or larger regional spectral wave models. This constraint results in local engineering and scientific organizations, reconstructing their own spectral boundary conditions. For coastal models, this is a reasonable assumption, assuming that the single parameterization is accurate and a representation of a non-multimodal sea state. The South African Weather Service (SAWS) Marine unit recently launched their coupled, operational wave and storm surge forecasting model. The aim of the SAWS Wave and Storm Surge (SWaSS) platform was to provide accurate, high-resolution coastal forecasts for the entire South African coastline. The present investigation thus presents the validation of the spectral wave component of the coupled system, developed in Delft3D. Various wave boundary reconstructions are investigated together with the two most used and well-known whitecapping formulations. Validation is performed with both in situ wave-rider buoy data (at nine locations along the coastline) and regional remotely sensed, along track, altimetry data. Full model performance statistics are provided, and the accuracy of the model is discussed.