OCELOT: Direct Atmospheric Forecasting from Heterogeneous Earth Observations Using a Graph-Transformer Hybrid Model
This study presents OCELOT (Observation-Centric Estimation and Learning for Outlook Trajectories), a global machine-learning forecasting system that predicts future Earth observations directly from heterogeneous satellite and in-situ measurements. Unlike data-driven weather models trained on gridded reanalysis states, OCELOT operates natively in observation space, preserving instrument-specific sampling, viewing geometry, and measurement characteristics. The system combines per-instrument graph-attention encoders, a shared spherical icosahedral latent mesh, a hybrid sliding-window Transformer/spatial graph neural network processor, and metadata-conditioned decoders to produce forecasts up to 12 h ahead. OCELOT is trained on observations for the years 2015 through 2023, validated on the year 2024, and evaluated out of sample on 2025 observations across satellite radiances, radiosondes, aircraft, and surface networks. In the 2025 evaluation, OCELOT produces spatially coherent +12 h forecasts across independent observing systems: microwave temperature-sounding channels show RMSE values of 1.24-1.87 K, while the more surface- and cloud-sensitive AVHRR infrared window channel shows a higher RMSE of 3.95 K. Vertical profile diagnostics show physically consistent radiosonde and aircraft temperature structure. Surface forecasts remain stable through 12 h, with 2-m air-temperature RMSE increasing from about 3.2 K at +3 h to about 3.6 K at +12 h. In paired observation-space comparisons, OCELOT remains less accurate than operational GFS but substantially outperforms persistence at longer lead times for 2-m temperature and 10-m wind components. These results demonstrate that observation-space forecasting can recover large-scale atmospheric structure and provide meaningful short-range skill without reanalysis supervision.