Artificial snow clouds: when cloud seeders use satellites to make more rain?

Imagine being able to make clouds rain more. That’s exactly what cloud seeding does — a technique that tries to boost rainfall in areas where water is scarce. A team of researchers studied this practice in the United States, focusing on three regions: Lake Tahoe, the Santa Rosa Range, and the Ruby Mountains. To trigger clouds, ground-based generators release silver iodide (AgI), a substance that helps ice form inside water droplets. But how do we know if it actually works? Scientists used satellites like GOES-R, whose multispectral cameras capture details about cloud temperature, thickness, and phase. They also analyzed NEXRAD radar data to see what happens below. Near Lake Tahoe, clouds responded quickly: a shift from liquid droplets to ice was detected, meaning clouds evolved differently when seeded. The result? More hail and rain. But not everywhere. In the Santa Rosa Range, clouds responded weakly, likely due to warm and dry conditions. In the Ruby Mountains, results were mixed. This study shows that cloud seeding doesn’t work the same everywhere — it heavily depends on local weather conditions. Satellites, however, have become key tools in understanding whether clouds are truly responding.

Cloud seeding relies on well-known microphysical principles called the 'cloud invigoration effect' or 'secondary ice process.' When silver iodide (AgI) is introduced into clouds containing supercooled water, the iodide particles act as crystalline nuclei for ice formation. This process promotes ice particle growth at the expense of water droplets, accelerating the transition from liquid to solid phase. The ABI (Advanced Baseline Imager) aboard the GOES-R series provides high-frequency data on cloud microphysical properties such as cloud top temperature, optical thickness, and phase indicators (frozen vs. liquid). Combined with NEXRAD radar data, this allows tracking of the full hydrometeorological cycle, from initial ice formation to hail or rain development. In favorable cases, such as near Lake Tahoe, sudden cooling of cloud tops (down to -20°C), increased opacity, and delayed cloud dissipation are observed, indicating greater persistence and productivity. Conversely, under strong thermal instability or low humidity, the effect weakens. The study emphasizes that integrating satellite observations, radar, and in-situ data is essential for assessing the operational effectiveness of cloud seeding, especially in data-sparse regions.