We can definitely say that cloud seeding enhances snowfall under the right conditions," said Sarah Tessendorf, a scientist at the National Center for Atmospheric Research (NCAR) and co-author of Quantifying snowfall from orographic cloud seeding, published in Proceedings of the National Academy of Sciences in late February. She was one of a group of scientists who used a combination of radars and snow gauges to measure the impact of cloud seeding on snowfall. They observed that clouds injected with silver iodide generated precipitation at multiple sites, sometimes creating snowfall where none had existed.
The study provides the most comprehensive evidence to date that cloud seeding can generate rain or snow. The study cautions that clouds must be present to produce precipitation and that results are dependent on atmospheric factors such as local winds.
"The seeding produces ice and that ice can form snow, but is it enough additional snow to make it cost effective?" asked Ms Tessendorf. "For water managers, the bottom line is the amount of snowpack that you're building over the whole winter and how much runoff it will generate. We are looking into some promising approaches to address those bigger questions, but we still have plenty of work to do to get there."