Wave energy spectra for the southwest coast of India

Abstract

Typical wave records from 4 shallow water locations of southwest coast of India are subjected to spectral analysis. The observed spectra in general have prominent peak (<i>Tp</i>) in the range 0.06 to 0.125 Hz throughout the year. This main peak is at the higher frequencies during monsoon and there is a relative shift to the lower frequencies during the rest of the year. In general, the spectra all along the coast are multipeaked and the possible reasons are discussed. Various spectrally obtained parameters are examined. The spectral moments and significant wave height show maximum values during the monsoon season. The peakedness parameter <i>Qp</i> varies between 0.9 and 3.6 and the slope of the high frequency side of the spectrum m, varies between 1.46 and 7.11, with a mean of 3.04 during monsoon and 4.79 for the rest of the year. The consequences of these values are discussed in detail. Among the different theoretical spectra compared, Bretschneider spectrum fits 75% of the cases followed by scott spectrum. The latter, however, overestimates the shallow water high energy conditions. These conditions may be represented by Toba spectrum with an ɑ value of 0.062 and suitably selected <i>u</i>_* value. The Kitaigorodskii <i>et al</i>. spectrum is suitable for the highest observed energy conditions. The autocorrelation functions show high variability and indicate occurence of wave groups along this coast.