Aurora 1.5: Extending open foundation models for weather and Earth-system applications
Microsoft released Aurora 1.5, an open update to its Earth-system foundation model, adding 22 new weather variables, hourly forecasts, and ensemble forecasting to improve atmospheric modeling and decision-making across sectors.
Aurora 1.5 expands the open foundation model for Earth-system forecasting by introducing 22 new weather variables, bringing the total to 26, alongside hourly temporal resolution and probabilistic ensemble forecasting. Developed by Microsoft Weather as an extension of the original Aurora model from Microsoft Research AI for Science, the update aims to provide researchers and developers with a broader, more detailed view of atmospheric conditions for evaluation and adaptation. The model’s open availability supports organizations requiring additional data, infrastructure, and operational assurance to integrate weather intelligence into their workflows.
The update enhances Aurora’s relevance for sectors such as energy, agriculture, transport, and resilience planning by improving coverage of surface, pressure-level, wind, temperature, humidity, precipitation, and radiation fields. Hourly forecasts enable finer operational guidance, while ensemble forecasting addresses model uncertainty by generating multiple simulations to estimate possible outcomes. Microsoft highlights that Aurora 1.5’s ensemble approach outperforms the state-of-the-art ECMWF dynamical ensemble on 88.9% of evaluated targets, demonstrating its potential for high-impact applications.
Aurora 1.5’s ensemble capability was developed through multi-stage fine-tuning, including controlled perturbations and optimization for probabilistic forecast quality. Evaluations on 2024–2025 tropical cyclones showed substantial reductions in track errors, with the ensemble median achieving roughly one-third lower error compared to the original Aurora. Beyond weather forecasting, partners like Terradot are leveraging Aurora-derived weather representations to advance carbon dioxide removal research, demonstrating the model’s broader applications in climate mitigation and public-interest science.
Microsoft Weather, the team behind AI-based forecasting across Windows, Bing, Copilot, Edge, and MSN, plans to extend Aurora 1.5’s capabilities with additional enterprise-focused models. The team, which has delivered high-quality global forecasts for over seven years, emphasizes that foundation models should complement—not replace—physics-based systems and domain expertise. Aurora 1.5 is available as an open-source resource, with Microsoft Weather offering managed services and integrations to support organizations in evaluating and deploying weather intelligence responsibly.