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How Cloud-Seeding Boosted California's Latest El Niño Storms

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Don’t be too quick to thank El Niño for the last wave of storms that blessed the West Coast with swamped reservoirs, replenished snowpack, and spectacular flaming palm trees. Turns out that El Niño had a little help—precipitation was increased by an estimated 15 percent thanks to cloud-seeding.

According to the Los Angeles Times, LA’s Department of Public Works and North American Weather Consultants cranked up to 10 cloud-seeding machines into action Sunday night as the storm rolled through, which ended up dumping plenty of rain and snow in the region.


Seeding clouds is a relatively simple process: Devices either mounted on the ground or installed on planes spray silver iodide into the moist air, which allows the air to form ice particles at warmer temperatures. This accelerates a process called cloud condensation, where water vapor globs onto those particles, making clouds more likely to produce droplets of precipitation.

It’s a practice that dates back to the 1950s and is still relatively common in places like China, which famously used it to produce sunny skies for the Beijing Olympics. (It can also be used to suppress inclement weather.) But I hadn’t heard of it being used in California for so long that I assumed it was a technology that was on the outs. It’s expensive, for one, and even when performed exactly right, it’s still not a sure thing.


Turns out the last time cloud-seeding was used in Southern California was back in 2002—but not necessarily due to cost. Conditions haven’t been ideal in recent years. The drought that’s paralyzed the West over the past five years hasn’t delivered much promising moisture to work with, since cloud-seeding requires an existing storm in order to make more rain. But even in the years before 2009, Southern California had suffered some crippling wildfire damage due to especially nasty fire seasons. Making an already powerful rainstorm too powerful would have triggered mudslides and flooding.

Apparently, everything Sunday was just right: a big storm was coming that already promised plenty of moisture with no potential risk due to recent wildfires. Let’s just say the gamble paid off.

[Los Angeles Times]


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