Sixty Days of Ocean, With Conditions
TL;DR for operators Neptune is a global ocean and sea-ice emulator that produces daily states out to 60 days. On held-out 2019-2021 reanalysis data, its 1° model generally beats training-set climatology for most variables and preserves large-scale temperature, sea-surface-height, ocean-heat-content, ENSO, and Indian Ocean Dipole structure well into the forecast horizon. The qualification problem begins when the forecast is examined by variable, region, and spatial scale. Currents and mixed-layer depth deteriorate more rapidly, energetic current systems remain difficult, fine-scale velocity variability is smoothed, and some sea-ice regions become less reliable at long lead times. The 0.25° version produces higher-resolution output but does not uniformly improve forecast diagnostics. ...