Analysis of the global swell distributions using ECMWF Re-analyses wind wave data

The existence of three well-defined tongue-shaped zones of swell dominance, termed as ‘swell pools’, in the Pacific, the Atlantic and the Indian Oceans, was reported by Chen et al. (2002) using satellite data. In this paper, the ECMWF Re-analyses wind wave data, including wind speed, significant wave height, averaged wave period and direction, are applied to verify the existence of these swell pools. The swell indices calculated from wave height, wave age and correlation coefficient are used to identify swell events. The wave age swell index can be more appropriately related to physical processes compared to the other two swell indices. Based on the ECMWF data the swell pools in the Pacific and the Atlantic Oceans are confirmed, but the expected swell pool in the Indian Ocean is not pronounced. The seasonal variations of global and hemispherical swell indices are investigated, and the argument that swells in the pools seemed to originate mostly from the winter hemisphere is supported by the seasonal variation of the averaged wave direction. The northward bending of the swell pools in the Pacific and the Atlantic Oceans in summer is not revealed by the ECMWF data. The swell pool in the Indian Ocean and the summer northward bending of the swell pools in the Pacific and the Atlantic Oceans need to be further verified by other datasets.