JCOPE-FGO: an eddy-resolving quasi-global ocean reanalysis product

Abstract

Abstract In the present research, we provide a brief description and assessment of the oceanic fields analyzed in the newly developed eddy-resolving quasi-global ocean reanalysis product, named the Japan Coastal Ocean Predictability Experiments-Forecasting Global Ocean (JCOPE-FGO). This product covers the quasi-global ocean with a horizontal resolution of 0.1° × 0.1°. Validations of analyzed temperature and salinity fields by JCOPE-FGO against in situ observations revealed that our product can capture various aspects of observed hydrographic structures in the world ocean, including frontal structures near the surface and thermohaline properties of water masses, as well as their spatiotemporal variability. Furthermore, we have assessed dynamical fields analyzed in JCOPE-FGO using satellite altimeters and surface drifters, and found that our product can represent the mean state and variability of the upper ocean circulation in many regions. A notable feature of JCOPE-FGO is the inclusion of an updated global river runoff, and impacts of river forcing have been assessed by an additional reanalysis experiment without river forcing. We found that the removal of continental river discharge leads to dramatic changes in the near-surface salinity and related fields around river mouths of large rivers, but large changes are mostly confined to narrow regions near the coast. As an example of the substantial impact of river runoff, we discuss the dispersion of low-salinity water from the Mississippi river to the Gulf of Mexico: a comparison between the analyzed salinity fields from both reanalysis products with those from satellite observations demonstrated that the inclusion of river runoff is essential for an accurate representation of its seasonal variability. Several key issues that warrant further improvements are discussed for future development.