Comparison and assessment of three wave hindcasts in the North Atlantic Ocean

Abstract

This paper compares and evaluates three wave hindcasts in the North Atlantic Ocean: ERA-Interim, NOAA/CFSR and HIPOCAS.The assessment was performed using satellite data from the GlobWave Project.It concerns the second part of a research project that aims to characterize differences among reanalyses and to calculate wind and wave error maps using satellites.The first step of this study inter-compares the hindcasts within a spatial-temporal approach.Besides, the analysis was also divided into overall conditions and extreme events.The second step evaluates each hindcast independently using satellite data.In order to compare and evaluate the three datasets, coincident periods and grid domain were determined, which corresponds to the interval between 1979 and 2001, latitudes between 15and 72North and longitudes between 66West and 7East.Results for the overall non-extreme conditions indicate that the three wave hindcasts are very similar and have small errors (less than 0.5 metres); NOAA/CFSR (based on the WAVEWATCH III model) presents the largest waves, followed by HIPOCAS and ERA-Interim (both based on the WAM model).NOAA/CFSR and especially HIPOCAS at European waters tend to overestimate the measurements while ERA-Interim tends to underestimate.For extreme events, the differences increase significantly (up to 2.5 meters) and HIPOCAS presented the highest waves, followed by NOAA/CFSR and ERA-Interim (severely underestimated).A simple joint wind and wave analysis concluded that WAVEWATCH III presented the best modelling in terms of bias but was over-performed by WAM used in the ERA-Interim project regarding the root mean square error and scatter index.