A Three-Dimensional Barotropic Model of the Response of the Australian North West Shelf to Tropical Cyclones

Abstract

A three-dimensional barotropic model using a -coordinate or depth transformation, and forced with tropical cyclone wind and atmospheric pressure fields has been applied to the continental shelf and slope regions of the Australian North West Shelf. The atmospheric pressure field of the cyclone causes a nearly isostatic sea level response and weak currents. In an unbounded ocean the wind field would produce currents that circulate around the center of the cyclone and eject water, thus tending to reduce sea level. The coastline forms a boundary for the ejected water resulting in a large sea level rise and strong currents between the cyclone path and the coastline. The model provides a good description of the vertical current shear as observed at a number of moorings during two different cyclones. Sea level rises are accurately modeled and a reasonable description of observed current strengths is achieved. However, the predicted currents and sea level changes at offshore stations are sensitive to the track followed by the cyclone and often this not known with sufficient accuracy.