However, the directional wave spect

However, the directional wave spectrum could be more blurred if the convolution process is repeated excessively,which may render the wave systems indiscernible. An energy level for a noise threshold of 1% and 2% of the total energy in the spectrum is suggested by Portilla et al. (2009) to remove the noise energy, especially in the observed spectrum. Consequently, by applying the noise energy threshold and iterative convolution procedures, the noise of the spectrum is filtered out and important spectral features are preserved, alleviating the dependence of excess arbitrary parameters set by previous methods proposed by Guillaume (1994),Hasselmann et al. (1996), and Voorrips et al. (1997).