Abstract
In a spectrum-based wave model, estimation of the surface displacement-based (significant) wave height H and (significant) wave period T is conducted by multiplying the square root of 0th spectral moment m0 by a constant value such as α =4.004 and multiplying a -1st moment/0th moment ratio m-1/m0 by another constant value such as β =1.000 respectively. But analyses of numerically-simulated samples and measurement samples indicate that these coefficients of α and β may depend on any of the spectral width parameters QP, κ01 and so on and that each of them can be approximated by use of QP- or κ01-powered linear expression with an upper limit of α =4.004 or β =1.000. The constant value case for α and β definitely yields greater estimates of wave height H and period T than the variable value case. This leads to either rectification of overestimation in wave hindcasting toward more proper estimation or degeneration of proper estimation to underestimation. The former tendency in Typhoon 1106 case and the latter tendency in Typhoon 0918 case were confirmed through detailed comparison between SWAN-based hindcasts and measurements for wave heights and periods at many GPS buoy stations deployed along the offshore areas of the Pacific coasts of Japan.
