HF ocean radar can produce maps of surface current in coastal ocean and
estuarine waters by providing coverage in both the space and time dimensions.
The deployment of COSRAD in Port Phillip Bay for two successive five-day
periods provided hourly values of surface currents over the topographically
complex area at the south end of the bay. Analysis of the current data
provided tidal ellipses for the validation of numerical models, with resultant
residual currents of the order of 0·05 m
s–1. The repeated hourly maps were the basis for
producing Lagrangian tracks; most tracks resulted in trapped paths which
remained for long periods of time in the matrix of channels and sand-banks. A
‘tidal run’ technique was developed to calculate the length of
Lagrangian tracks over one phase (ebb or flood) of the main tidal component.
All tidal runs were about equal to, or shorter than, the length of the
relevant channel; this indicates that tidal forcing is not effective in
flushing the bay. In contrast, the observed residual currents can be an
effective flushing agent if they persist for three days or longer. It is
suggested that phenomena on the scale of meteorological to seasonal forcing
are the effective flushing agents for Port Phillip Bay.
A METHOD FOR DECOPOSING SURFACE CURRENTS MEASURED BY HF OCEAN RADAR INTO TIDAL, DRIFT AND TSUNAMI CURRENT COMPONENTS
