HiRO-ACEv2: Simulating extreme weather at 3 km resolution for a fraction of the cost
Hugging Face has introduced HiRO-ACEv2, an updated climate emulator system designed to simulate extreme weather at a 3 km resolution. The system combines a coarse 100 km AI model called ACE with a downscaling model called HiROv2. According to the source, HiRO-ACEv2 generates global climate data at about 1/300th of the cost of traditional high-resolution atmospheric models.
The Core Development
We introduce HiRO-ACEv2 , the newest update to our High Resolution Output Ai2 Climate Emulator (HiRO-ACE) system. HiROv2 can reproduce even extremely rare rain, wind, and pressure events with high accuracy, while the full system can generate global 3 km climate data at about 1/300th the cost of X-SHiELD, a high-resolution global atmospheric model that explicitly simulates storms and other small-scale weather.
HiRO-ACE, introduced earlier in 2026 , has two parts: ACE, an AI model that operates at a coarser 100 km resolution, and HiRO, a model that sharpens those coarse outputs into fine 3 km detail. The biggest change in HiRO-ACEv2 is the new downscaling model, HiROv2, which can now 1) predict several high-resolution fields at once instead of just rainfall, so it can capture a much wider range of extreme weather, and 2) has improved skill in predicting extreme events.
Our main focus with HiRO-ACEv2 was to simulate extreme events well. Changes to how we train HiROv2 improved its ability to reproduce the most intense rain, wind, and pressure values. When given coarsened X-SHiELD data, it matches the target simulation's high-resolution statistics to within 3%, even for events so rare they occur only once in a million data points. It also accurately estimates the total energy of tropical cyclones, including storms it never saw during training, and generates hurricanes with realistic eyes and rain bands, though winds and pressure around the eye remain somewhat more lopsided than in X-SHiELD. Additionally, HiROv2 realistically generates strong winds flowing down mountain slopes.
Strategic Perspective & Ecosystem Impact
We also trained an updated version of ACE for this system. Over a 10-year simulation, its hurricanes, average climate patterns, and overall distributions of rain, wind, and pressure all line up well with X-SHiELD. That tells us ACE's coarse simulations are a solid foundation for producing long-term high-resolution climate data.
Putting HiROv2 and ACE together, we generated a full year of global 3 km data. Its statistics closely match X-SHiELD's, even though HiRO was working from a simulation ACE ran on its own rather than from real X-SHiELD data. Across a 10-year run, the energy of HiRO-ACEv2's hurricanes is comparable to X-SHiELD's over the same period, and snapshots from that run show a variety of other extreme events that resemble those in X-SHiELD.
An example of a strong hurricane in the North Atlantic, generated during the 10-year HiRO-ACEv2 simulation.
Why it matters
This development demonstrates how combining coarse AI models with efficient downscaling can drastically reduce the computational cost of high-resolution climate modeling. It provides researchers with an accessible, inexpensive tool for generating multi-year extreme weather data.