When an unexpected rainstorm leaves you soaking wet, it is an annoyance. When a drought leads to fires, crop failures and water shortages, the significance of weather becomes vitally important.
If you could control the weather, would you?
Small amounts of rain can mean the difference between struggle and success. For nearly 80 years, an approach called cloud seeding has, in theory, given people the ability to get more rain and snow from storms and make hailstorms less severe. But only recently have scientists been able to peer into clouds and begin to understand how effective cloud seeding really is.
In this episode of “The Conversation Weekly,” we speak with three researchers about the simple yet murky science of cloud seeding, the economic effects it can have on agriculture, and research that may allow governments to use cloud seeding in more places.
Katja Friedrich, a professor of atmospheric and oceanic sciences at the University of Colorado, Boulder in the U.S., is a leading researcher on cloud seeding. “When we do cloud seeding, we are looking for clouds that have tiny super-cooled liquid droplets,” she explains. Silver iodide is very similar in structure to an ice crystal. When the droplets touch a particle of silver iodide, “they freeze, then they can start merging with other ice crystals, become snowflakes and fall out of the cloud.”
While the process is fairly straightforward, measuring how effective it is in the real world is not, according to Friedrich. “The problem is that once we modify a cloud, it’s really difficult to say what would’ve happened if you hadn’t cloud-seeded.” It’s hard enough to predict weather without messing with it artificially.
Cloud seeding is usually done by planes equipped with devices – like the one attached to the wing of this plane – that spray silver iodide into the atmosphere.
Zuckerle/Wikimedia Commons, CC BY-SA
In 2017, Friedrich’s research group had a breakthrough in measuring the effect of cloud seeding. “We flew some aircraft, released silver iodide and generated these clouds that were like these six exact lines that were downstream of where the aircraft were seeding,” she says. They then had a second aircraft fly through the clouds. “We could actually quantify how much snow we could produce by two hours of cloud seeding.” That effect, according to research on cloud seeding, is an increase in precipitation of somewhere around 5% to 20% or 30%, depending on conditions.
Measuring the effect on precipitation – whether rain or snow – directly may have taken complex science and a bit of luck, but in places that have been using cloud seeding for long periods of time, the economic benefits are shockingly clear.
Dean Bangsund is a researcher at the University of North Dakota who studies the economics of agriculture. “We have a high amount of hail damage in North Dakota,” said Bangsund. For decades, the…