Source Tracing of the Swell Energy: A Case Study of the Pacific Ocean

During the resource crisis, swell energy received an increasing amount of attention due to its stability, huge energy storage and dominant role in the mixed wave. Investigation of the swell propagation is beneficial for wave energy forecasting, swell monitoring and warning and so on. However, little research has been conducted on this topic so far. The traditional method is to choose a region in advance (short as pre-chosen region) and then detect the propagation termination of the swell of this region, which is limited in effectiveness because the swell of the pre-chosen region may not propagate to the area focused. Based on the 40-year European Centre for Medium-Range Weather Forecast (ECMWF) re-analysis (ERA-40 wave reanalysis), this study proposed a back-stepping method to trace the source of swell energy. The Clipperton Island waters are selected as a case study. Results show that the back-stepping method is an effective way to trace back the source of swell energy. The swells of the Clipperton Island waters mainly come from the winter Hemisphere. The swells need about 120 hours to propagate from the Hawaii waters to the Clipperton Island waters, while 180 hours to propagate from the Maria-Theresa Reef to the Clipperton Island waters.