Clouds are warehouses that rarely ship. Most of the water that floats over a mountain range keeps floating. Cloud seeding gives a cloud that was already close to raining the nudge it needs: a speck for water to grab onto. That’s it. That’s the trick.
THE PRIMER
04
Cloud seeding,explained over coffee.
01
DISPERSION
A drone flies into a winter storm cloud and releases a fine mist of silver iodide. The amounts are tiny: grams per flight, not tons.
02
ATTRACTION
The cloud is full of water that is below freezing but has nothing to freeze onto. Each particle acts like a seed of ice, and cloud droplets latch onto it and freeze.
03
ACCRETION
Every new ice crystal keeps collecting droplets and grows into a snowflake, gaining weight with each second it stays inside the cloud.
04
PRECIPITATION
When the snowflakes get too heavy for the cloud to hold, they fall. Snow banks in the peaks all winter, then melts into rivers, reservoirs and aquifers through summer.
WHY BOTHER?
10.5B
acre-feet of water pass through the atmosphere, roughly three times what all of humanity uses in a year. The warehouse is full. We just never learned to ship.
IS IT SAFE?
≪ EPA
Silver iodide is used in trace amounts. Concentrations in snowpack measure orders of magnitude below EPA drinking-water limits, monitored season after season.
DOES IT WORK?
+20%
The World Meteorological Organization cites seasonal precipitation increases of up to 20 percent from well-run winter programs.
The part that’s new: for seventy years, cloud seeding worked the way a lottery ticket works: you paid, you hoped, you argued about the results. Rainmaker’s bet is validation: weather radar that watches the phase change happen inside the cloud, so every operation ends with a number instead of an opinion. Target. Seed. Validate.