Ai2 Releases HiRO-ACEv2: Simulating 3km Extreme Weather at 1/300th Cost

Ai2 released HiRO-ACEv2 on October 14, 2026, an AI system designed to reduce the computational cost of global climate simulations to approximately one-three-hundredth of traditional high-resolution models. The tool enables researchers to access over ten years of 3-kilometer resolution data on extreme rainfall, wind, and pressure events at a significantly lower cost.

Traditional high-resolution atmospheric models like X-SHiELD explicitly simulate small-scale weather such as storms but incur prohibitive computational costs, limiting large-scale long-term simulations. HiRO-ACEv2 addresses this through a two-stage architecture: the ACE model first generates coarse 100km resolution climate fields, which are then refined to 3km resolution by the newly developed HiROv2 downscaling model.

According to Ai2's technical report, when given coarsened X-SHiELD data, HiROv2 matches the target simulation's high-resolution statistics to within 3%, even for rare events occurring once in a million data points. The system also accurately estimates tropical cyclone energy and generates hurricanes with realistic eyes and rain bands.

Currently, HiRO-ACEv2 is limited to climate scenarios matched to its X-SHiELD training data and cannot yet predict future warming scenarios or historical observational datasets like ERA5. These results are based on Ai2's self-reported benchmarks and have not yet been independently reproduced.