Narrow Results

A new system for directional wave spectrum observation was developed by improving the Nationwide Ocean Wave information network for Ports and HArbourS (NOWPHAS). Either Doppler Type Wave Directional Meter (DWDM) or Wave Gauge Array System is adopted for wave observations. Directional spectra are estimated by EMLM method for DWDM and EMEP method for array system. For the convenience, the obtained directional spectra are expressed as the frequency banded wave heights and directions corresponding to the wave spectrum. Examples of annual statistics of the directional wave spectra at three typical NOWPHAS wave stations are introduced in this paper.

A Bayesian method for estimating directional wave spectra from the Doppler spectra obtained by HF radar is examined using data acquired during the SCAWVEX project. Applicability, validity and accuracy of the Bayesian method are demonstrated compared with the directional spectrum observed by a directional buoy. In addition the estimated spectra are compared with Wyatt (1990) and the Bayesian method is found to be more robust against noise. Necessary conditions of the Doppler spectral components to be used to estimate a reliable directional spectrum for the present method are also discussed.