This year, Romania has taken an important step in the fight against drought and extreme weather phenomena by acquiring the first airplane designed to boost rainfall. The plane, bought from the US company Fargo Jet, is the first of four. The initiative represents a significant national effort to combat the impact of drought, a growing problem as average annual temperatures rise and extreme weather in Europe intensifies.
One of the most effective methods of stimulating precipitation is seeding clouds with silver iodide (AgI). This method was first used in the 1940s in the USA, and silver iodide acts as a condensation nucleus in clouds, helping to form ice crystals.
How the cloud seeding process takes place
Dr. Physicist Daniel Florea, Program Director of the Operator of the Hailfall Combating Unit Moldova 1 Iasi explains the cloud seeding process.
“The silver iodide is dispersed into the atmosphere by torches mounted on the airplane’s wings to reach the clouds at the desired region and altitude. At negative temperatures, below zero degrees Celsius, silver iodide acts as a frozen condensation nucleus, providing a surface on which supercooled water can freeze and form ice crystals. Water vapor begins to adhere to the ice crystals, causing them to grow in size. As they get bigger and heavier, they fall, and if they pass through warmer layers of air, they melt and reach the ground as rain,” he said.
Although there have been concerns raised in the public about the safety of silver iodide use, research and use in other past programs demonstrate that the risks are minimal. The amount of silver iodide used in a seeding mission is very small. For example, a torch used by an airplane weighs about 150 grams, of which only 12 grams is pure silver iodide.
“This amount in relation to the area on which it is distributed leads to a small amount per area, amounting to about 30 milligrams per hectare,” added Dr. Florea.
Studies from other weather modification programs with decades of active operation show that silver iodide is found in extremely low concentrations in snow and water, comparable to the amount of silver found in a cup of tea after mixing with a teaspoon of silver. A 2015 study by researchers such as James Fisher and Shawn Benner concludes that silver from cloud seeding poses no risk to the environment or wildlife, and has only been detected in extremely low concentrations.
This conclusion is also iterated in the study published by the US Weather Modification Association in July 2009, where research carried out in Greece assessed the impact of silver iodide use on different environmental components, including soil, plants, precipitation and aquatic organisms. More than 2500 soil samples from areas subjected to cloud seeding were analyzed and found no significant silver accumulation or negative ecological impact. The study also highlights that silver iodide used in such programs does not accumulate in local ecosystems and remains chemically inactive.
The Academy of Agricultural and Forestry Sciences “Gheorghe Ionescu-Șișești” has also issued a document confirming that, according to international research, there is no conclusive scientific evidence of toxic effects of the substances used in these procedures. These conclusions justify the use of the method from a safety and sustainability perspective in the context of climate change.
Laboratory results: Cloud seeding did not affect soil and water
The IAA has, over the years, carried out experimental research programs on precipitation enhancement by aviation, and a laboratory accredited by the European and the Ministry of Environment has analyzed soil and meteorological water samples from the areas concerned. The results of these tests showed that cloud seeding did not generate higher concentrations of substances than those found naturally.
Over time, the agents used for weather modification have evolved into increasingly complex formulas. In addition to silver iodide, there are other substances used in interventions, such as dry ice and liquid nitrogen, which are designed to cool part of the cloud so that the supercooled water vapor in that area freezes, producing additional condensation nuclei. Hygroscopic materials such as sodium chloride or calcium chloride are also used in clouds that do not reach negative temperatures to attract water vapor and stimulate droplet formation, eventually resulting in precipitation.
By acquiring this first precipitation-stimulating airplane, Romania is taking an important step in managing water resources and combating the effects of drought. The seeding of clouds with silver iodide, together with other substances used in this field, is a viable solution to counter climate change and protect the country’s agriculture and ecosystems.
