Open Access Atlas of Global Spectral Wave Conditions Based on Partitioning

Abstract

An open access atlas of wave spectral characteristics at global scale is presented (GLOSWAC). This atlas is based on a recently developed technique for deriving spectral statistics, following the concept of partitioning. This development has been possible due to the parallel release of the wave spectra variable from the ERA-Interim archive of the European Centre for Medium-Range Weather Forecast (ECMWF). Although wave spectra are commonly available nowadays for wave analysis and forecasting, standard integral wave parameters are still in dominant use, both in practical and scientific applications. Although integrated parameters can give a good account of the wave spectral distribution in unimodal cases, they are subject to serious shortcomings when the sea state is bimodal or multi-modal. This issue can be easily tackled with the use of partitioning approaches. Spectral partitioning allows identifying the different wave components with different meteorological origin present in the spectrum. These components can be represented by their integrated parameters, which are much more meaningful than the averaged ones for the whole spectrum. Apart from the increased consistency, this method allows to summarize spectral information, offering the possibility to develop wave spectral statistics. Based on a statistical descriptor, the Probability Distribution of Spectral Partitions (PDS), which is the main outcome from GLOSWAC, the local long-term wave systems can be identified and characterized. In addition, several other spectral parameters are computed and distributed in a web format. For illustration, an arbitrary reference location is used here to guide the interpretation and the use of the information derived.