The use of water has been growing at more than twice the rate of population increase in the last century. Water scarcity has also begun affecting every continent and the threat of drought is increasing. But a team of researchers at Tsinghua University in Beijing have found a solution to trigger rainfalls in drought-prone regions using powerful and low-frequency sound waves.
The team conducted a weather manipulation experiment on the Tibetan Plateau in 2020. The Chinese researchers recorded an increase in rainfall of up to 17 percent by pointing a giant loudspeaker at the sky.
The research team, led by Professor Wang Guangqian from the Tsinghua University's State Key Laboratory of Hydro-science and Engineering, said: "The total annual atmospheric water vapor resource in China is about 20 trillion tonnes. [But] only 20 percent forms natural precipitation that reaches the ground, and the precipitation conversion rate in western regions is even smaller."
Change of Cloud Physics
The study was published last week in a peer-reviewed paper Scientia Sinica Technologica. According to the South China Morning Post, the researchers said that the sound wave used to trigger rainfall might have changed the physics of cloud, but the cause of the phenomenon would need further investigation.
Wang said that unlike other artificial rain-making technologies, the sound wave-based process produces no chemical pollution and requires no aircraft or rockets. He also added that there is the possibility of "remote control with low cost".
However, the critics accused Wang of wasting taxpayers' money, while others said that even if the sound stimulation works to increase the rainfall, it would cause sound pollution for the people and the animals who are the inhabitants of the region.
The sound created by Wang's loudspeakers at a frequency of 50 hertz is barely perceptible to most human ears but at a volume of around 160 decibels or the same noise level produced by a running jet engine at a full speed. When the sound waves reached the cloud, almost 1,000 meters above the ground, the strength would drop by 30 decibels, researchers said.
The team believes that the increase in the rainfall is caused by the oscillation and coalition of smaller particles into bigger ones. As per the study, the rainfall was up to 17 percent higher in areas within the device's effective range which is about the radius of almost 500 meters from the sound creator.
According to the report, a researcher from the Institute of Atmospheric Physics under the Chinese Academy of Sciences in Beijing said that this experiment would have to be replicated many times to accumulate more data about the outcome.
The unnamed expert also expressed his doubts about the idea of the connection between sound and rainfall. He said that there was no physical evidence to support such theory and "the subject remains more of a myth than science".
If Wang's experiment receives global recognition and other researchers find this as a useful method, it could solve the continuous threat of drought in several places around the world.
While the groundwater levels are reducing dramatically along with the increase of global population, the water future is uncertain. "Water scarcity will be exacerbated as rapidly growing urban areas place heavy pressure on neighboring water resources. Climate change and bio-energy demands are also expected to amplify the already complex relationship between world development and water demand," said the UN.