Data Assimilation Meetings at Reading

Date Meeting type Speakers
29 April 2015
Agriculture 1L14
Invited speaker Ben Timmermans (University of Southampton)
Uncertainty in a numerical wind-wave model
The modelling of ocean waves is carried out routinely by meteorological agencies worldwide. However, little is know about the source of the uncertainty in the predictions of waves produced, and sources can be numerous depending on the specific application. Historically it was felt that the dominant source of uncertainty originated from incomplete knowledge and expression of forcing winds. However more recent studies have focused on the underlying physical processes and their representations, with some authors questioning whether the limitation of the current modelling approach has been reached. Recently, methods for the statistical analysis of complex computer models, including models such as those used for wave prediction, have been developed. In this talk I will describe statistical emulators and how I applied them to the spectral wind-wave model Wavewatch III to perform the first ever uncertainty analysis for a wave model. Sources of uncertainty included wind forcing, together with input parameters associated with input and dissipation, and wave-wave nonlinear interaction source term parameterisations. Probabilistic sensitivity analysis was performed in order to quantify the influence of each input, and identify nonlinear response in output (typically in terms of wave heights and periods). Experiments were performed for modelled waves in idealised cases and on Lake Michigan.

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