Infragravity Wave Generation by Wind Gusts

Through the analysis of propagation times of infragravity wave packets along ray paths, reanalysis data, and our field measurements in the East Mediterranean, we find evidence of deep water infragravity wave generation by offshore storms. We confirmed the results also using deep water pressure cell measurements in the Pacific. The known nearshore generation mechanism showed large discrepancies with the observed infragravity energy near Aogashima, Japan, during winter. A new model of deep water infragravity wave generation is developed, based on nonlinear interactions of wind wave triads with submesoscale wind oscillations. The observed underprediction of infragravity waves is resolved using this new gustiness-based model. The new source term is found to be of importance during strong storms in the open ocean and underlines the importance of accounting for submesoscale wind oscillations in wind wave models.