Ai2's HiRO-ACEv2 emulates extreme weather at 3 km for a fraction of X-SHiELD's cost
Ai2 introduced HiRO-ACEv2, the newest update to its High Resolution Output Ai2 Climate Emulator system, which pairs a coarse 100 km ACE model with the HiRO downscaling model that sharpens outputs to 3 km detail. The main change is the new HiROv2, which predicts several high-resolution fields at once instead of only rainfall and, according to Ai2, matches X-SHiELD's high-resolution statistics to within 3% even for events occurring once in a million data points. Ai2 also retrained ACE and says a combined run produced a full year of global 3 km data that closely matches X-SHiELD; however, HiRO only works with the ACE version tuned to X-SHiELD and cannot yet handle other climates such as a warmer future or ERA5.
Ai2 says producing global high-resolution data with HiRO-ACEv2 costs roughly 300 times less than running X-SHiELD, and the models are available to download with tutorial notebooks and a web demo.
HiRO-ACEv2: Simulating extreme weather at 3 km resolution for a fraction of the cost
October 14, 2026
Ai2
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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.