Velocity bunching model for modelling wave spectra along east coast of Malaysia

Abstract

This paper presents the application of the velocity bunching model to detect the wave spectra pattern. We have developed the azimuth cut-off model which is estimated from the velocity bunching theory to model out the significant wave height. The velocity bunching model utilized two ERS-1 images (First European Remote Sensing Satellite). These two ERS-1 images have been acquired with the different monsoon periods. Several steps have been used to simulate the significant wave height from the velocity bunching model, these were: the real ocean wave spectra simulated from the in situ wave data, and the SAR wave spectra, extracted by applying two-dimensional Fourier transform (2-DFFT). Finally, the significant wave height was estimated based on the azimuth cut-off arising from the velocity bunching model. Two hypotheses were established in modelling the wave spectra from the SAR images: (i) azimuth cut-off was based on velocity bunching, which has been used to model the significant wave height with high accuracy, and (ii) velocity bunching model has been used to map the SAR wave spectra into ocean wave spectra. In the present study, a specific ERS-1 images of the South China Sea has been considered. No significant differences were found between the velocity-bunching model and ocean wave spectra model where ERS-1 wave spectra has been found to be dominated by the azimuth fall-off effects. Furthermore, the velocity bunching model produced wave spectra pattern approximately closed to the real ocean wave compared to the SAR wave spectra. The highest rate of r2 (0.69) occurred when the significant wave height increased. It has been concluded that the velocity bunching model could be used as the best fit model for estimating the significant wave height traveled along the azimuth direction.