Probabilistic reconstruction of global sea surface temperature using generative diffusion models

TL;DR

This paper introduces SAGE, a diffusion-based probabilistic framework for reconstructing global sea surface temperature, effectively capturing uncertainty, integrating heterogeneous data, and improving climate prediction accuracy.

Contribution

SAGE is a novel, physically consistent generative model that performs observation-conditioned SST reconstruction without requiring satellite or in situ data during training.

Findings

SAGE reduces SST reconstruction errors compared to existing products.

SAGE improves 10-day SST forecast accuracy.

SAGE captures El Nino onset and evolution better than conventional methods.

Abstract

Accurate reconstruction of global Sea surface temperature (SST), which dominates the air-sea coupling and global climate variability, underpins climate monitoring and prediction. Existing SST reconstruction products primarily provide one deterministic field derived from heterogeneous satellite data and in situ observations, limiting their ability to represent observation uncertainty and to support probabilistic forecasting. Here, we introduce Satellite and in situ Adaptive Guided Estimation (SAGE), a diffusion-based uncertainty-aware generative framework for probabilistic SST reconstruction. SAGE learns a physically consistent prior from historical SST data and performs observation-conditioned posterior sampling without requiring satellite or in situ data during training, enabling flexible state inference from heterogeneous observations. Through a progressive data-fusion strategy, observations from two FengYun-3D polar-orbiting satellites constrain basin-scale structures, while sparse in situ measurements serve to refine local anomalies and extremes. The resulting ensemble SST fields well capture observational uncertainty and scale-dependent variability. Validation against independent in situ observations shows that SAGE substantially reduces reconstruction errors compared with widely used operational products. When used to initialize forecasting systems, SAGE-generated SST fields substantially reduce 10-day SST forecast errors relative to current operational analyses. At the climate scale, SAGE-driven forecasts of the 2023-2024 El Nino event show added value in capturing its onset and intensity evolution compared to conventional approaches. Our results demonstrate that SAGE represents a step toward a new paradigm for ocean state estimation and climate prediction.