Wave conditions encountered by ships { A report from a larger shipping company based on ERA5

This study reports about the wave conditions encountered by the fleet of Maersk Line. Herein, wave conditions refer to integral wave parameters in terms of significant wave height, zero-upcrossing period, and wave direction (equivalently relative wave heading), but main focus is on the significant wave height. The study includes data from 189 container ships, where auto-logged data has been collected over a three-years period (2017–2020) during operations in the majority of the world’s larger oceans. In total, the data corresponds to 1 million hours of operation. The encountered wave heights are compared with the information from wave scatter diagrams given by the Global Wave Statistics (British Maritime Technology, 1986). The study shows that weather routing and seamanship have an effect, but the effect is not as pronounced as reported in a previous study (Olsen et al., 2006). The study also presents findings in relation to the temporal and spatial variation in encountered wave height along ship routes at consecutive wave points spaced by the sailing distance in 30–120 min. It is shown that the variation can be large and, as such, the concept of “stationary conditions” might be compromised sometimes in the analysis of wave-ship interactions.