Global extreme wave estimates and their sensitivity to the analysed data period and data sources

Abstract

Abstract In the lack of wave measuring buoys operating over extended periods, the use of wave hindcast data or satellite observations is indispensable for estimating global extreme wave heights. However, the results may depend on the analysed wind wave sources and the length of the analysed period. The sensitivity of the estimated extreme significant wave heights (SWH) to the analysed data sources and periods is investigated in this study. Global extreme wave heights are estimated using ECMWF Reanalysis v5 data (ERA5), global wave hindcast developed based on Simulating WAves Nearshore forced by the Japanese 55-year Reanalysis (SWAN-JRA55), satellite altimeter observations, and long-term wave buoy measurements. Both Annual Maximum fitting to the Generalized Extreme Value Distribution (AM-GEV) and Peaks Over Threshold fitted to the Generalized Pareto Distribution (POT-GPD) models are used. The results show that the global extreme SWH estimates considerably depend on the analysed data sources. The relative differences observed between the analysed data sources are > 20% in large part of the world. Thus, by increasing the analysed data periods, the relative differences in extreme SWH are mainly lower, but they can reach 30% and are more important using AM-GEV. Besides, by comparing the extreme values from reanalysis and hindcast wave data to those from long-term wave measurements, underestimations of up to 2 m are observed for a return period of 100 years in the North-West Atlantic and North-East Pacific.