Cloud Seeding

Imagine with me a bitter-cold, cloudy morning, calling for a hot breakfast, maybe with a cup of coffee or even a sweet cup of cocoa.  Enjoying the coziness of the warm breakfast and preparing for the start of another demanding day, a small airplane can be seen tracing circles high above Idaho’s mountain ranges.  Seeing the sky streaked with planes is nothing new to this valley, and so you go on your way, thinking little of the plane.

But what if I told you that small plane was the combination of a little science, a little magic, and little faith to bring the miracle of snow?  It’s true!  On board that little plane are tiny,  microscopic particles that are released into the clouds to increase the snowfall of the storm. 

I say magic because it seems impossible to create water, or snow in this case, out of thin air.  A magic trick for sure!  But it’s not. It’s not even science fiction, it’s cloud seeding. And for many in agriculture, those tiny particles could mean the difference between another long dry year without water and one with enough snowpack to feed crops, pastures, and cattle herds all season long.

The science of cloudy seeding isn’t new, but with decades of research, innovation, studying and greater understanding, the scene of a little plane flying through the clouds is becoming far more common.  As droughts and dry seasons impact the country, and countries around the world, giving Mother Nature a helping hand with the irrigation has become a must to keep the water flowing.

To understand cloud seeding, first we need to understand precipitation in general.  There is always moisture in the air.  We see it as it collects together in the form of clouds.  That warm, moist air naturally rises and as it does, it cools and the moisture condenses, just like we see on the outside of a glass, just into a cloud.

Inside the cloud, those moisture molecules are moving around, colliding into other drops of dust or similar particles in the atmosphere.  When a water particle collides with another, it will bond and grow, using the dust particle as a sort of nucleus or landing pad.  As more particles of water attach through more collisions, the droplet will get heavy, heavy enough gravity will pull it to the ground.

In a cloud that has supercooled water, the water particles will freeze as they land on the dust nucleus, then onto each other in a hexagonal lattice formation.  The hexagonal platelets grow into a prism, the different branches of ice grow at different rates depending on the conditions. The frozen particle or snowflake will continue to grow until it becomes heavy enough to fall from the sky. 

Simply put moisture rises, cools, forms droplets or crystals, and eventually falls as precipitation, the temperature determining whether it falls as rain or snow.

Cloud seeding helps a storm produce more moisture that it would otherwise by providing more particles for the droplets to attach to.  It doesn’t produce the storm, but makes the most out of existing storms.  

A seeding agent, most commonly Silver Iodide (AgI), is released into an existing storm cloud by either a plane or by ground-based generators. This process only happens if a storm system moves in that has conditions that are conducive of effective cloud seeding operations. Seeding particles are released during active storms with specific conditions conducive to ice formation.

As the molecules are dispersed within the targeted clouds, the seeding particles grow into ice crystals at the expense of the SLW in the cloud and become large enough to fall and create snow, essentially “wringing out” more water from the cloud before it moves out of the region.

The primary seeding agent used is silver iodide (AgI) , a microscopic particle that has a similar hexagonal shape as naturally occurring ice.  Not only does the similar shape make silver iodide a great seeding agent but also the fact that AgI functions at warmer temperatures than naturally occurring ice, allowing for ice formation, precipitation, to begin sooner.  So not only does this seeding technique provide more starting points for ice molecules, but at an earlier rate.

This technology is being used around the world to both increase more snowpack but to also to encourage earlier rainfall from incoming weather systems.  In 2008, cloud seeding was used at the Beijing Olympics in an effort to hurry storms through before certain events would take place. 

The United Arab Emirates government has invested heavily in cloud seeding since the 1980s, first using planes and more recently with drones to seed clouds in the arid desert environment. According to recent reporting, some of these efforts have reportedly increased rainfall in certain areas by 10–30% under favorable conditions.  

Midwestern states have used cloud seeding to prompt the early rainfall of storms that would have otherwise become crop destroying hailstorms.  A true phenomenon to manipulate storms in any capacity.

Cloud seeding isn’t a new concept and some doubts continue to mingle the effectiveness of the strategy.  The first critique is whether the technique actually produces added precipitation or not.  In 2017 The Seeded and Natural Orographic Wintertime clouds: the Idaho Experiment (SNOWIE) took a collection of weather instrumentation used both on the ground and in the plane that enabled them to capture a 4D model of the atmosphere to study what happened when they introduced cloud seeding. 

The SNOWIE research project was the first to demonstrate ‘unambiguous’ evidence that cloud seeding can produce winter precipitation, debunking the idea that increased snowfall was a mere coincidence.

The second critique is the financial efficiency of such a project.  Running the complicated numbers, the short answer is yes.  Places with suitable climate, terrain, and occasional storms, particularly in agriculture- or snowpack-reliant regions, cloud seeding seems to offer a high return on investment relative to cost.  Idaho Power, a big supporter of the research, reportedly produced extra water at roughly $3.50 per acre-foot which is far cheaper than many alternative water-supply options like water banking or some forms of water import.    

A final critique of cloud seeding is the environmental impact AgI will have.  Fortunately, AgI is inert in the natural environment, meaning that it is a stable compound and does not react with other chemicals. It is also “insoluble” in water so it cannot “disassociate” or break apart to become free silver (Ag+) available to aquatic organisms.  Extensive research has found no impact on the environment, making the compound the ideal seeding particle.

With such positive findings to cloud seeding, the Idaho Department of Water Resources has developed a cloud seeding program.  Its focus is simply to increase the winter snow pack that will create a trickle effect to increase the water supply of both surface and groundwater.  Utah’s government is starting into a new initiative to use cloud seeding in hopes to replenish the Great Salt Lake through direct precipitation and snow pack.  

The benefits of cloud seeding seem to be endless as countries around the world see water shortages and increasing needs.  Cloud seeding, of course, won’t solve drought and water shortages but it certainly can play a crucial role in making the most of what Mother Nature has to offer.  It will do little without clouds already dotting the skies, but you can be sure that when the opportunity arises, squeezing even a drop or two more of rain will do someone some good.

Maybe the next time you look out at the cold, cloudy sky with your hot breakfast in hand and see a small plane streaking across the mountains, you can raise your cup in thanks for the little extra moisture coming your way from a tiny, microscopic silver particle you didn’t even know existed.