How Cloud Seeding Works to Induce Rainfall?

Have you ever looked up at the sky, noticed dark clouds, and predicted that rain was on the way, yet it never came? Why doesn’t rain when it should?

Looking closely there is something interesting with rainwater, namely: it is not just water. When you collect rainwater, you will notice that it generally contains sediment;  The evidence for this comes straight forward. When the rain dries onto your car windshield or the windows of your house, it’s easy to notice that it leaves a fine powder. Therefore the answer to the question above is obvious: when you see dark clouds, you expect to rain, but it still doesn’t, that means there are not yet enough water molecules attached to the tiny particle of power matter, ready to make a water droplet heavy enough to fall on the ground. Besides, if the air humidity is too low, there won’t be enough amount of water up there and despite dark clouds it won’t rain. This piece of physics was at the heart of one of the most extraordinary experiments of the 20th century. When scientists seeing dark clouds in the sky and rain still didn’t happen, they wondered: what if there is a way to make those clouds release rain? What if the scientists can took it upon themselves to deliberately control the weather and induce artificial rain? And they discovered how. The method is called Cloud Seeding.

WHAT IS CLOUD SEEDING?

Cloud seeding is a scientific method of weather modification designed to enhance a cloud ability to produce rainfall and snowfall, while also reducing hail damage.

Essentially it focuses on inducing short-term changes in precipitation. It cannot create rain clouds from zero, but it can artificially induce rain in naturally formed clouds. The process involves introducing tiny particles into specific types of clouds. These particles then act as nuclei around which water droplets form, which can ultimately lead to rain or snow. To understand how cloud seeding works, we first need to grasp how rain occurs. Here’s a simplified breakdown of the process:

– Water from lakes, rivers and oceans evaporates due to the sun, tuning into water vapor.This vapor rises into the sky and cools down after reaching a certain altitude, forming tiny water droplets. Although these droplets are not individually visible, when millions of them collect they take the form of clouds. As more and more droplets combine, they become large and heavy enough to fall, which is when we say it’s raining–

It all starts with the natural principle that in order to rain or snow, the water droplets or ice crystals need something to form onto. Let’s take simple example from daily life: think about maybe if you were taking a steamy shower. When you’re done, the walls of the bathroom are wet. Maybe the mirror is fogged up too. So, the humidity in the air didn’t just form into raindrops in your bathroom, right? It attached itself onto the mirror. So it goes when ice crystals forms and water droplets form, they need to form onto something. Those formation supports are called condensation nuclei or condensation nucleus. They are natural in the atmosphere everywhere. For example, things like: pollen, sea salt (under the form of microscopic spray that comes off of the ocean), dust and any of a variety of things like that can be a condensation nucleus.

Now how does cloud seeding fit into this process?

The process was invented in 1946 by Vincent Schaefer, an American scientist. Schaefer and his team determined through laboratory experiments that if they dispersed tiny silver iodide (AgI) crystals into the atmosphere, these crystals would act as dust or smoke might, and become the nucleating droplets —the seeds—of clouds. In certain clouds naturally formed, the conditions may be such that the water droplets are too small to fall as precipitation, in other words the process of droplet formation and accumulation isn’t functioning effectively enough to produce rain. To change the condition within these clouds, cloud seeding is employed which consists of aircraft, rockets or ground-based generators releasing specific particles into the clouds.

Silver iodide (AgI)  is a chemical that has a structure that the water likes to gloom onto or ice can easily accrete to, which would, in turn, produce snow and rain. Hence the most common used materials for cloud seeding: are silver iodide (AgI) and hydroscopic substances like table salt (NaCl). However various other substances can be successfully used as well, such as:

• frozen carbon dioxide – dry ice (CO₂₎,
• calcium chloride (CaCl₂),
• potassium iodide (KI),
• sulfur dioxide (SO₂),
• bismuth tri-iodide (BiI₃),
• propane (C₃H₈), and others. 

As they can attract moisture, these particles act as nuclei providing something for the water droplets to hold onto, allowing more droplets to gather around them. As result, this creates a snowball effect, causing the droplets to grow larger and larger. When they become heavy enough they fall as rain or snow. Early experiments showed that given perfect circumstances, not every time, but if there was a saturated layer of the atmosphere and conditions were just right, they could increase the output of a cloud from what it would normally have rained to about 10% more. The only condition being that clouds must be already naturally formed.

Delving into the scientific complexities reveals two main techniques:

I – HYGROSCOPIC SEEDING = for warm clouds, =  with is a technique that introduces salt particles that encourage water droplets to merge.

II – GLACIOGENIC SEEDING = for super-cooled clouds =  which can be done as:

• as Static Cloud Seeding which increases the efficiency of precipitation formation by introducing a chemical agent into supercooled clouds or
• as Dynamic Cloud Seeding which aims to enhance air currents, allowing more water droplets to rise and freeze.

Whether dispersing salt particles (NaCl) in liquid clouds or triggering ice production in super-cooled clouds with silver iodide (AgI), each method has a unique approach. The clouds deemed suitable for these methods include warm season clouds associated with convective systems such as thunderstorms as well as cold season clouds often found in mountainous regions. Of course, by seeding the air you control only one aspect of the weather: Cloud Formation. So if the moisture content of the air is low, no amount of cloud seeding will make it rain. But if the air is full of water, then using this technique to increase snowfall over ski resorts, or reduce the risk of hail damage on crops during storms, can be productive.

The cloud seeding technique is an art as much as it is a science, but as widely used as it’s been for decades, many dispute its effectiveness. At its essence, cloud seeding ambitiously attempts to assist Mother Nature by introducing into the clouds additional “nuclei” around which water condenses, stimulating precipitation. However, this technological tool prompts intriguing questions such as:

• Could cloud seeding be a solution to drought or aid in fighting forest fires?
• Could increased precipitation in one area inadvertently trigger a drought elsewhere?
• Might cloud seeding cause excessive rain, leading to flooding?

The answers aren’t straightforward, as conjuring clouds remains beyond its current scope.

Still, though, Russia seeded clouds over Moscow every year. Their aim was to clear moisture from the air by making it rain, ensuring that their May Day celebrations were accompanied by blue skies. Both Russia and Thailand are successfully using it for suppressing heatwaves and wildfire. In the aftermath of the Chernobyl nuclear disaster in 1986, cloud seeding was used to make enough rain to remove radioactive particles from the atmosphere as well.

The US military employed the technique for a different aim during the Vietnam War—they used it to extend the monsoon season on the Ho Chi Minh Trail; this was called Operation Popeye, and its mission was to “make mud not war.”

Today, the USA, China, India and Australia are applying the cloud seeding potential for maximizing water utilization during rainfall for drought mitigation. In the United Arab Emirates, the technique is actively used to expand its agricultural capabilities and battle extreme heat.

So Cloud Seeding  is still a topic of debate, Advocates highlight its efficacy, with studies indicating a  10 to 15% increase in rainfall. Conversely, skeptics raise cautionary flags, emphasizing potential hazards to public safety and the environment. Decades of research have yielded static and dynamic seeding techniques, showing indications of effectiveness by the late 1990s.