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 climbs into a cold, wet cloud and releases a whisper of silver iodide. Grams, not tons. The particles scatter through the supercooled mist.
02
ATTRACTION
Water in the cloud is colder than freezing but has nothing to freeze onto. The particles look, to a water molecule, like ice. Moisture rushes to them.
03
ACCRETION
Droplets pile on and crystals grow, snowflakes assembling themselves around each seed, growing heavier by the second.
04
PRECIPITATION
Gravity does the last mile. Snow falls on the peaks, banks all winter, and melts into rivers, reservoirs and aquifers all 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.