TEHRAN — Deploying proper techniques for cloud seeding can produce economic benefits for the country, an expert with the Meteorological Organization has said.

“Implementing standard and scientific techniques can create an opportunity for economic advancement while inappropriate and ineffective measures can result in abnormal precipitation patterns and even flood,” Tasnim news agency quoted Amin-Hossein Naqshineh as saying. 

Cloud seeding, a form of weather modification, is a method to change the amount or even type of precipitation. Rainfall occurs when super cooled droplets of water – those that are still liquid but are at a temperature below the usual freezing point of zero centigrade – form ice crystals. Now too heavy to remain suspend in the air, these then fall, often melting on their way down to form rain.

Even in dry areas the air usually contains some water. This can be made to come together and form ice crystals by seeding the atmosphere with chemicals such as silver iodide or dry ice. They work to promote rainfall by inducing nucleation – what little water is in the air condenses around the newly introduced particles and crystallizes to form ice. The ‘seeds’ can be delivered by plane or simply by spraying from the ground.
 
“Cloud seeding is possible in the country and we have the necessary infrastructure as well as the scientific know-how needed to implement such projects,” Naqshineh suggested. 

He further explained that by employing cloud seeding techniques precipitation amounts can be increased by 20 percent in some regions. However, he warned, “quite the reverse outcomes can occur in case we implement defective techniques.”

This can lead to less precipitation or extreme precipitation and floods, he added.

Many countries are now using cloud seeding to increase their precipitation amounts, this technique can be expensive but in case it is implemented properly and work it can be highly advantageous, Naqshineh concluded. 

How cloud seeding in viewed internationally 

In an article titled “cloud seeding critics and converts” published in the How the Stuff Works website it is stated that internationally, Russia, Thailand, South Africa and Caribbean nations have all tried their hand at cloud seeding, and all with mixed results. Australian scientists­ conducted numerous experiments, discovering that static seeding didn't appear to be effective over Australia's plains but was very effective over Tasmania.

In 2003, the United States National Academy of Sciences declared that 30 years of studies had not produced "convincing" evidence that weather modification works. Nonetheless, the American Meteorological Society claims that some studies on cloud seeding show a 10 percent increase in rain volume.

Cloud seeding is rather expensive, though potentially cheaper than other projects, like diverting rivers, building new canals or improving irrigation systems. So, the allure of cloud seeding may redirect attention and funding from other projects that could be more promising. Then there are questions about altering weather. Are some areas taking moisture out of the air that would have fallen as rain in another region? And if regions are experiencing drought due to climate change, isn't better to invest the funds and exert efforts to tackle the causes of global warming?

Moreover, despite reassurances from cloud-seeding companies, concerns also remain about exposure to silver iodide toxicity and soil contamination. Other safety issues are more transparent. In China, wayward munitions have damaged property and even killed one person in May 2006. The Chinese government contends that it has improved training, licensing and safety practices. 

Scientists may not be sure if cloud seeding actually works, but despite the skepticism, China is moving forward. The nation spends $60 to $90 million a year on weather modification, in addition to the $266 million spent from 1995 to 2003. The government plans to produce 1.7 trillion cubic feet (50 billion cubic meters) of rain a year through the practice. 

Is cloud seeding just a way of sweeping pollution and climate change under the rug to ensure you don't have to schedule a rain date? Or is it merely a matter of altering weather to your benefit? However you look at it, it's not likely to go away any time soon. In fact, some scientists have already proposed building fleets of massive, unmanned ships to seed clouds over Earth's oceans to provide a cooling counter to carbon dioxide-induced global warming. 

In the end, cloud seeding has strong supporters, but it remains controversial.

MQ/MG