The influence of wind gustiness on estimating the wave power resource

Abstract

There are many uncertainties associated with the wave models used to generate regional wave energy resource assessments. One of these sources of uncertainty is the temporal resolution of the wind input. Wave models are typically forced with 3-hourly synoptic wind fields. In reality, winds are highly turbulent and exhibit high spatial and temporal variability. Therefore, by using 3-hourly wind fields to force wave models, much of the high frequency nature of the wind climate is not captured, and this could lead to substantial errors when estimating the wave energy resource of a region. Until now, research has focused on the importance of spatial model resolution, with little attention given to the importance of temporal resolution. Here, we use the SWAN wave model to simulate an idealised storm event within an idealised model domain characteristic of the North Sea. The extent to which fluctuating wind affects wave power is examined, with a test case where wind, in the absence of gustiness, was input as the control. Wave power is a function of the wave period and the square of wave height, both of which are altered as a result of high frequency wind input. Our results indicate that, for this idealised study, the inclusion of wind variability at sub-hourly time-scales can lead to a difference in wave height of up to 35%, which corresponds to a difference of up to 56% in simulated wave power. Consequently, understanding and accurately simulating the high frequency nature of winds can improve the accuracy of regional wave energy resource assessments.