On the bandwidth parameter of wind-wave spectra

In Light of the analysis of the physical implication and underlying assumption of the bandwidth parameter epsilon of wave spectrum, a time-averaging method is used to evaluate epsilon of the JONSWAP spectrum for different sea states. The resulting values of epsilon, which vary from 0.44 to 0.53 depending on the dimensionless fetch, are physically meaningful and reasonable. The same method is also used to compute epsilon from wind-wave records measured in a flume under different wind speeds at different fetches. The computed values of epsilon, which vary with wind fetches and speeds too, are compared with those evaluated for the JONSWAP spectrum.