A 30-MHz ground-wave ocean surface radar has been deployed inside the Great Barrier Reef where the water is sheltered from ocean swell. The spatial resolution of the radar is 3 km radially and 3.5� in azimuth. In each cell a 102.4-s time series is used to determine radial surface currents, wind directions, root- mean-square wave heights and wind speeds. Coincident observations of sea-wave spectra, surface currents and boundary-layer winds are used to evaluate the radar performance and to modify some of the methods of data analysis to suit these conditions. Surface current values are observed by the radar to an accuracy of �0.05 m s-1, wind directions to �10� , root-mean-square wave heights to 0.15 m and wind speeds to �3 m s-1. In some spectra, the peak in the second-order continuum caused by the non-directional sea- wave spectrum is not resolved from a second-order resonance line. This disallows the derivation of the period of the dominant sea wave on a routine basis.

A simplified, physically intuitive model of diffuse scattering of radio waves from a rough surface is used to present a self-contained derivation of first- and second-order cross sections, essentially in agreement with the standard expressions. Incoherent addition of the second-order contributions (electromagnetic and hydrodynamic) leads to a cross section which is slightly different from the more rigorously derived cross sections of Barrick (1972b) and Johnstone (1975). A surface current v has been incorporated in this model, with the main change to the cross section being a frequency shift of the entire spectrum by an amount Llw = -2ko . v.