Sensitivity analysis of wind input parametrizations in the WAVEWATCH III spectral wave model using the ST6 source term package for Ireland: Fid-Bau Portal

Sensitivity analysis of wind input parametrizations in the WAVEWATCH III spectral wave model using the ST6 source term package for Ireland

Fernández, Leandro / Calvino, Clément / Dias, Frédéric

Abstract

Abstract The performance of the third generation wave model WAVEWATCH III (version 6.07) using the ST6 source term package, developed by Zieger et al. (2015) and then updated by Liu et al. (2019), is investigated in the context of wave growth and dissipation in the west coast of Ireland. A sensitivity analysis is carried out to establish preliminary values of the parameters involved in the configuration of the wind input term $S_{i n}$ by tuning the CDFAC parameter to potentially eliminate a bias in the wind field and the $a_{0}$ parameter that controls the strength of swell decay due to wind effects. A system of nested structured grids is used to model long-distance swells generated in the Atlantic Ocean that propagate all the way to the west coast of Ireland. The bias, the root-mean-square, the correlation coefficient and the scatter index statistical parameters, and the probability density function are used to validate the model by comparing the significant wave height from four local buoys measurements with numerical results. Comparisons between measurements and numerical data show a good overall agreement. The most appropriate value obtained for the drag coefficient CDFAC is 0.9, which represents a 10% decrease from the value proposed in the last versions of the package. Depending on the buoy selected for the analysis, the values tested for the second investigated parameter $a_{0}$ lead to a reduction of the bias in the comparisons, together with a reduction of the other statistical parameters. These results confirm the values proposed in previous work for future developments.

Highlights • The performance of WAVEWATCH III using the ST6 source term package to describe wind generation is investigated. • The analysis is carried out by tuning the CDFAC parameter to potentially eliminate a bias in the wind field. • The $a_{0}$ parameter to control the strength of negative wind input is also tuned. • The probability density functions of the significant wave height are compared with buoy measurements.