I’m singing in the rain…

By Sériane Kenema

The first time, I heard about “man-made rain” I thought it was a joke. I was told by a friend in Beijing that the artificial rain was used to reduce the air pollution. Suspicious I decided to do my own research.

History

I quickly discovered that “man-made rain” is nothing new.  Discovered in July 1946 through a series of serendipitous events by two researchers from General Electric.

How it works?

Man-made rain is a weather modification process called “cloud-seeding”. In the ancient times, during periods of severe drought witches could be seen performing rain dances to bring back the rain. Today in the technology era, the new witches are the geo-engineers.

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The most common chemicals used for cloud seeding include: silver iodide, potassium iodide, dry ice (solid carbon dioxide) and in some cases liquid propane, which expands into a gas, has also been used.

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Cloud seeding can be done by ground generators, plane, or rocjet

 The effects from cloud seeding are almost instantaneous, it takes only minutes to see a visible increase in cloud size and precipitation levels.

China : World leader in cloud seeding

Through our courses we have learned about the success of Emperor Yu. As far back as 2150 BC he was made famous by his ability to control the Yellow River and stop the flood. Today China’s rulers face the opposite problem; water scarcity is threatening farms and industries.

In 1958, the cloud seeding technology was brought to the Middle Kingdom of China via Russia. In 2011, China spent $150 million on a single regional artificial rain program, for comparison the United State spends around $15 million per year. According to Reuters China’s Ministry of Finance aims to use the technology to create more than 60 billion cubic meters of additional rainfall annually by 2020.

With its horrendous air pollution and acute water shortage, China is a natural contender to be the world’s leading cloud seeder.

Global cloud seeding

China may have the most advanced technology when it comes to cloud-seeding, but it is far from the only nation with a water modification program. The World Meteorological Organization, lists over 52 countries who are trying to address large-scale shifts in temperature and precipitation brought about by climate change through similar programs, including 10 countries which started programs less than five years ago.

People across the globe are becoming increasingly more aware of the constraints that arid environments have on resources.

Apart from the environmental benefits associated with increased rainfall, there are economic opportunities for companies as well. In recent years, several commercial companies have grown offering weather modification services centered on cloud seeding. While some government operated, projects exist the most popular type of project involves coordination between the government and a private company, such as farms or hydropower stations. The largest such company, Weather Modification Incorporated, has operations worldwide and it claims prominently that its technology works.

PROS

  • Use in water scarce areas and those suffering from severe drought

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 Due to the increase in rainfall conditions such as famine can be avoided. Many countries which are experiencing severe drought can utilize this technology to alleviate their problems. Last year, the drought-stricken Indian state of Maharashtra spent $4.5 million on cloud-seeding.

  • Economic improvement for Agriculture

In some cases, this technology has been effectively used to suppress undesirable forms of precipitation, such as hail storms, which can cause damage to crops and urban areas. Given better weather conditions farmers would have the ability to grow and sell more crops. This would result in an overall improved economy for the region.

  • Economic improvement for Tourism

Aside from agriculture, dry and arid places which were previously considered as inhospitable could be transformed into new desirable vacation spots.

Additionally, as part of the 2008 Summer Olympics opening ceremony in Beijing to keep the stadium dry, cloud seeding was used. The rockets were launched into the sky prior to the cumulus nimbus reached the Olympic City, preventing the disruption of the events. Cloud-seeding is also occasionally used by major ski resorts to induce snowfall.

 CONS

  • Negative weather impacts

Cloud seeding is feared to ultimately change climate patterns even though it is also believed to regulate the weather. Some people argue that it would have rained anyway but in another location, the process leads to depriving other areas of precipitation.

  • Flooding

 It is doubtful in regions experiencing chronic water shortage that there is a system in place to deal with flooding. Hail and excessive snowfall are another risk to consider. During the winter of 2009, ice rockets were launched into the sky to induce rainfall during a four-month long drought, Beijing’s longest in 38 years. However, the temperatures dropped sharply and the precipitation fell as snow. The snowfall was heavier than expected leading to the closure of 12 main roads around Beijing.

  •  Health and Environmental impacts

Compared to other geo-engineering technologies, cloud-seeding is considered as a relatively environment friendly method. Still there is some concern about the uptake of elemental silver iodide in highly sensitive ecological conditions. Current research is showing that the silver generated by cloud seeding is fairly minimum (less 1%) of industry emissions into the atmosphere in many parts of the world, or even individual exposure from tooth fillings.

The long-term effects due to accumulation on the health of plants, animals (including humans), and the environment are not yet known. There are other processes, which require further research on their impacts and are worth investigating, such as shooting salt-and-mineral-filled bullets into the atmosphere.

Enhancing cloud seeding with biomimetics

Naturally occurring cloud seeding is called bioprecipitation. Bacteria present in some clouds have evolved to use rainfall as a means of dispersing themselves. The cloud forming and the rain are a key element of their bacterial life cycle. The most known bacterium species are the Pseudomonas syringae, which have proteins on their surface allowing water to freeze at temperatures around the melting point of ice (0 °C).

 So far, those bacteria have been used most frequently by ski resorts. Ski resorts dose their snowmaking machines with the bacteria, Pseudomonas syringae, which have been found to outperform artificial cloud-seeding chemicals, suggesting it might be able to be used as a rain-maker, one day in the not too distant future. However there is still much research that needs to be done to better understand the protein composition of these bacteria before we can expect to see them used to trigger rain.

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