The directional-spectrum model of internal waves in shallow seas given by Xiao and Fang (1991) was used to analyze the observation data gathered in April

1981

in the sea off Sydney

Australia. Some reasonable results were obtained. The energy ratio between Wavemodes 1 and 2 was about 2 for most frequencies and was up to 8 at ω=0.23 cph. Wave components with frequencies 0.1–0.8 cph were generated in the deep sea

and propagated onshore

while those with frequencies higher than 0.8 cph were locally generated by the interaction between longshore currents and bottom topography. Several surveys were carried out in the sea off Sydney

Australia (Cresswell

1974

Cresswell and Boland

1981

and Fang

Boland and Cresswell

1984). The survey performed in April 1981 by Fang

Boland and Cresswell (1984) was outstandingly successful. To draw some deterministic and stochastic characters of internal waves

Fang

Boland and Cresswell (1984) and Fang (1987) analyzed these data gathered in 1981 and obtained some reasonable results. Using Schott and Willebrand's (1973) directional spectrum model of internal waves as reference

the authors

in another paper (Xiao and Fang

1991

denoted as XF for simplicity hereafter) established the eigenfunctions and dispersion relation of the vertically standing-internal-wave modes

derived an optimization method to estimate the directional spectra of internal waves

and obtained the confidence interval expression of the estimates. In the present work

the authors use the results of XF and data mentioned by Fang et al. (1984) to analyze the directional spectra of internal waves in order to detect the propagation properties of internal waves in more detail. In this paper

the basic hydrologic properties in the observation area are first briefly described

then the estimation and test of directional spectra

and finally

the results

are discussed. The physical meanings of the letters used in expressions here are the same as those used in XF

except for other descriptions.