Comparison Study of a Second-Generation and of a Third-Generation Wave Prediction Model in the Context of the SEMAPHORE Experiment

Abstract

Numerical wave prediction models presently used in the meteorological institutes are still of two types: the so-called second-generation and third-generation models. In this paper, the authors present a comparison of the performance of a second-generation model?the VAG model from Météo-France?and of the third-generation WAM model. These two models have been run with similar characteristics (same wind input, same resolution). Simple tests show the differences between the behaviors of VAG and WAM in typical situations (constant wind, rotating wind). Hindcasts have been performed in the general context of the SEMAPHORE experiment. A one-month hindcast over the North Atlantic domain has been run by driving both models with the same wind fields. A comparison between the model output and the available observations, including significant wave height from satellite measurements, is presented. The results show that VAG and WAM results are in a general good agreement with the observations, but also that WAM results are a little better than VAG when the satellite data are taken as a reference. A modification of VAG is then proposed, which allows the performances of VAG to be closer to those of WAM. This study shows that (i) the second-generation VAG model is nearly as good in predicting wave heights as the third-generation model WAM in spite of its poor representation of the nonlinear interactions and (ii) VAG has been improved when introducing the growth and dissipation terms of WAM instead of parameterizations taken from Golding.