What is cloud seeding?

Clouds can be stimulated to produce more rain and snow. But is this ethical?

A turboprop sprays chemicals over Thailand.

Humans may not be able to control the weather, but we can certainly change it. Cloud seeding is one way to artificially modify the weather. It is defined as the act of injecting chemicals such as dry ice (solid CO2), silver iodide (AgI), table salt (NaCl) into clouds to alter the behavior of weather outcomes.

According to the Weather Modification Association, at least eight states use seeding to increase precipitation, especially winter snowfall. Cloud seeding is a common tool used to address water scarcity caused by drought and snow drought, especially in the western United States. However, there is still intense debate surrounding its efficacy and ethical issues.

History of cloud broadcast< /strong>

While cloud seeding sounds super modern, it’s not a new concept. It was invented by General Electric scientists Vincent Shaffer and Irving Langmuir in the 1940s while researching ways to reduce icing in airplanes. Icing occurs when supercooled water droplets from clouds strike and immediately freeze on the surface of the aircraft, forming a layer of ice. The scientists reasoned that if these water droplets could freeze into ice crystals before combining with the aircraft, the threat of icing on the wings would be reduced.

Schafer tested the theory in the lab by exhaling into a deep freezer, so his breath created the “cloud.” He then placed various materials, such as soil, dust and talc powder, into the “cold box” to see which ones most stimulated the growth of ice crystals. When tiny dry ice pellets are thrown into the cold box, a cloud of tiny ice crystals forms.

Schafer and colleagues.

In this experiment, Schaefer discovered how to cool the temperature of the clouds, which triggers condensation, which produces precipitation. A few weeks later, General Electric scientist Bernard Vonnegut discovered that silver iodide was equally effective in glaciation because its molecular structure is very similar to ice.

The study quickly attracted widespread attention. Government companies are teaming up with General Electric to study how to cloud seed and weaken hurricanes in arid regions.

Cirrus Plan

< p data-track="12">In October 1947, artificial rainfall began to be tested in the tropics. The U.S. government dropped more than 100 pounds of dry ice on the periphery of Hurricane No. 9, also known as Cape Seb in 1947. The theory at the time was that the freezing carbon dioxide at minus 109 degrees Fahrenheit might neutralize the hurricanes caused by the heat.

Not only did the experiment produce inconclusive results; the storm had been moving offshore before diverting to make landfall near Savannah, Georgia. Although it was later revealed that the hurricane began to shift westward before planting its seeds, the public perception was that Project Cirrus was to blame.

Storm Fury Project, Sky Water Project and others< /em>

In the 1960s, the government commissioned a new wave of hurricane cloud-seeding projects. Known as Project Fury of the Storm, the experiment proposed that by seeding a hurricane’s outer cloud bands with silver iodide, convection would grow at the storm’s edges. This will create a new, larger (and thus, weaker) eye with less wind and strength.

It was later determined that seeding had little effect on hurricanes, because hurricane clouds naturally contain more ice than supercooled water.

From the 1960s to the 1990s, several more projects emerged. The Water in the Sky initiative, led by the U.S. Bureau of Reclamation, focuses on increasing water supplies in the western United States. U.S. weather modification programs dwindled in the 1980s due to a lack of convincing scientific evidence for the effects of intentional weather modification.

However, the Bureau of Reclamation’s 2002-2003 Weather Damage Correction Program, as well as California’s historic droughts of 2001-2002 and 2007-2009, have reignited interest in man-made Interest in rainfall, which continues to this day.

How cloud seeding works

In nature, precipitation occurs when tiny water droplets suspended in clouds become large enough to fall down without evaporating. These droplets grow by colliding and combining with neighboring droplets, and they are either frozen onto solid particles with a crystalline or ice-like structure, called ice nuclei, or attracted to dust or salt, called condensation nuclei.

This natural process is facilitated by injecting additional nuclei into the cloud, thereby increasing the number of water droplets that grow large enough to fall like raindrops or snowflakes, depending on the cloud Air temperature inside and under clouds.

These synthetic nuclei come in the form of chemicals such as silver iodide (AgI), sodium chloride (NaCl), and dryIce (solid CO2). All of these fire chemicals into the air from ground-based generators, or from aircraft that fire chemical-laden flares that disperse into the centers of precipitation-producing clouds.

In 2017, the United Arab Emirates, with nearly 250 seeding projects in 2019, began testing new technology for drones to fly into the clouds and generate electric shocks. According to the University of Reading, this method of charging ionizes the cloud droplets, causing them to stick to each other and thus increasing their growth rate. Since it doesn’t require chemicals like silver iodide (which is toxic to aquatic life), it could become a greener seeding option.

Is cloud seeding effective?

Although seeding is traditionally thought to increase rainfall and snowfall, but scientists have recently made progress in measuring the actual accumulation.

The 2017 winter cloud seeding study in Idaho used weather radar and snow gauge analysis to analyze signals specific to seeding precipitation. Seeding produced between 100 and 275 acre-feet of water — enough to fill nearly 150 Olympic-sized swimming pools — depending on when the cloud was seeded, the study showed.