Eddy-Resolving Global Ocean Prediction

Global prediction of the ocean weather e.g., surface mixed layer, meandering currents and fronts, eddies, and coastally trapped waves has been feasible only since the turn of the century when sufficient computing power and real-time data became available. Satellite altimetry is the key observing system for mapping ocean eddies and current meanders, but sea surface temperature, temperature and salinity profiles, and atmospheric forcing arc also essential. The multinational Global Ocean Data Assimilation Experiment GODAE has fostered the development of eddypermitting and eddy-resolving basin-scale to global prediction systems in several countries. In this work, the focus is on eddy-resolving global ocean prediction, the value of ocean model skill in dynamical interpolation of data and in forecasting, plus the increased skill gained from using eddy-resolving versus eddy-permitting models. In ocean prediction, one must consider the classes of ocean response to atmospheric forcing for different phenomena and regions. In ocean nowcasting, this is important in considering the relative impact of the atmospheric forcing and different ocean data types. In forecasting, these classes impact whether or not the timescale for oceanic predictive skill is limited by the timescale for atmospheric predictive skill or whether a coupled ocean-atmosphere model would be advantageous. Results from the existing eddy-resolving global ocean prediction systems demonstrate forecast skill up to 1 month, globally and over most subregions. Outside surface boundary layers and shallow water regions, the forecast skill typically is only modestly impacted by reverting toward climatological forcing after the end of the atmospheric forecast versus using analysis-quality forcing for the duration.