Introduction
Cloud seeding, the process behind artificial rain, is a well-known method of weather modification that aims to change the amount and type of precipitation. This is done by dispersing substances into the air that serve as cloud condensation. These substances provide a surface for condensation. Its objective is to increase precipitation and to reduce drought conditions.
The discovery of cloud seeding
Cloud seeding is a serendipitous discovery. It was introduced by chance by Dr Vincet Shaefer while researching aircraft icing and precipitation. In 1946, he breathed in cold box and noticed water vapors. He then added dry ice (Solid form of CO2) and to his amazement he noticed a blue haze and millions of microscopic ice crystals. On 13 November 1946, he dumped 2.5 kg of dry ice from a plane into a cloud. As a result he was able to produce rain leading to breakthrough of cloud seeding. Dr Berhard vonnegut, he used the salt AgI (silver iodide) to create surface for condensation. Silver Iodide has property to absorb moisture and attract water vapors. They are known as cloud seeds or cloud condensation nuclei. In recent times, cloud zapping is also introduced in which clouds are electrified to cause precipitation.
Applications
Cloud seeding was one of the revolutionary discoveries. Humans were able to control the weather. Since its discovery, cloud seeding is extensively being used by various countries for their own benefits. In 1955, Thailand started Thailand royal rainmaking project to counter effects of droughts. In 1993, Tamil Nadu in India also used cloud seeding to reduce effects of severe drought in Tamil Nadu.
Many countries even used it to stop the rain on a specific day by precipitating early. In 2008, China used this technique to stop rain during Beijing Olympics. China is planning to revive its shrinking Yangtze river by proper planning and implementation. Cloud seeding is being widely used to reduce size of hailstorms, reduce fog to prevent heavy damages. According to reports, heavy losses in agriculture sector were avoided by using this technology.
Long term impact on environment
Every technology has its pros and cons. In line with the research it is surprising to note that it has no lasting negative effects on environment. One of the reason behind this can be that we can only prepone the rain or change the area but we cannot increase the amount of rain or create more clouds. So far, experts have not detected any harmful effect of silver iodide on environment and health.
There is only one major example where cloud seeding was used for wrong purpose. In 1970s, during Vietnam war, America launched operation popeye that aimed to extend monsoon season in some areas of Vietnam. This was done to affect the military supplies. It is known as the case of meteorologial warfare.
Conclusion
In a nutshell, Cloud seeding is a limited technology. We can only control the time and place for rain but we can not increase the amount of rain. Overall, it is not helpful to fight against drought and issues like climate change. However, it is useful to stop rain in very important events.
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