Artificial ice crystals force water out of the sky
China is carrying out the greatest weather experiment ever. With silver iodide powder, meteorologists aim to make major quantities of precipitation fall on the Tibetan Plateau, so Asia’s largest water reservoir will not run dry.
Everybody is talking about the weather, but nobody can do anything about it – except for China. The world’s most populous nation is carrying out history’s most extensive meteorology experiment to ensure vital precipitation for one of the world’s driest regions.
The weather makers aim to force the clouds above the Tibetan Plateau in South-Western China to give off huge quantities of rain and snow to the 1.6 million km2 region.
The large-scale project is known as Tianhe – “Sky River” – and is still in its initial stage. On steep mountain slopes in Tibet, scientists from the government-owned China Aerospace Science and Technology Corporation and a team from the Tsinghua University in Beijng have installed 500 rainmaking machines, which are combustion chambers including a silver iodide solution. Silver iodide has the same structure as ice crystals and functions as a type of double of real ice. When heated, the warm air carries silver iodide particles to the clouds. In the clouds, the particles make the existing water vapour condense into water drops, which grow bigger, only finally to fall as rain or snow.
In the years to come, tens of thousands more combustion chambers will be installed on the Tibetan Plateau to supply the clouds with silver iodide particles. The method is known as cloud seeding, and it is a relatively simple and cheap way of manipulating the weather. Each combustion chamber costs about $10,000, and if everything turns out the way scientists expect it to, the investment will indeed be worthwhile. According to calculations, the annual precipitation in the drought-ridden plateau will increase by up to 10 billion m3 annually.
Satellites monitor the monsoon
The Tibetan Plateau is located at an altitude of 4,000-5,000 m above sea level. It is known as the water tower of Asia, and justly so. Ten of the continent's largest rivers originate on the huge plateau, supplying about 1.3 billion people with fresh water. Global warming made temperatures in the plateau rise by an average of 1.9 degrees in 1961-2012, and in several places, the precipitation is now less than 10 cm annually, corresponding to the quantity of precipitation falling on the Saraha Desert in one year. According to climate researchers,
temperatures in the Tibetan Plateau will have risen by five degrees in 2100, leaving millions of people without drinking water. But already now, China feels the consequences of the lacking precipitation.
In 2011, 40 % less rain than the usual level fell near the Yangtze River. The lack of precipitation made its water level fall, destroying much of the rice crop, shutting down several waterworks, and halting the supply of drinking water for millions of people.
The people behind the Heaven River project aim to avoid similar disasters in the future. By means of 30 different weather satellites, meteorologists will monitor the monsoon activity above the Indian Ocean. When the weather system hits the Tibetan Plateau, the combustion chambers are activated, so the wind carries the silver iodide particles to the clouds to cause rain. And if the combustion chambers are not enough, the clouds could always get extra silver iodide from the fleet of planes, drones, and rockets that also form part of the Heaven River project.
Works better than rain dance
China is not by far the only nation acting as a rainmaker these days. Since American chemist Vincent Schaefer invented cloud seeding in 1946, the interest in weather manipulation has risen steadily. According to a report published by the World Meteorological Organization, 56 countries are carrying out cloud seeding projects.
Apart from China, which is the world’s leading cloud seeding nation with some 55 billion t of artificially-produced rain annually, particularly the United Arab Emirates are counting on cloud seeding. The oil-rich nation not only manipulates the clouds above its own deserts – it is also hired by countries such as Australia and the US to increase precipitation above some of the countries’ most thirsty agricultural areas.
It is not only silver iodide that is used to seed the clouds. Nations such as Thailand and the US also use dry ice or salt, such as potassium
chloride or sodium chloride that also make water vapour condense in the clouds and collect around salt. As a general rule, silver iodide and dry ice are used in high-lying, cold clouds, whereas salt is used in warm, low-lying clouds.
Although the chances of more rain are very much welcomed by millions of people, everybody is not equally thrilled.
Iran’s former president, Mahmoud Ahmadinejad, on several occasions accused Europe of deliberately using cloud seeding to steal rain from the thirsty Iranian people.
In China, rainmakers have also been much debated. In 2004, meteorologists seeded the clouds outside the city of Pingdingshan in the drought-ridden Henan province. Half an hour later, 100 mm of rain fell on the thirsty inhabitants. But when the clouds reached the neighbouring city of Zhoukou, only 27 mm of rain remained in the clouds, making the citizens accuse the meteorologists in Pingdingshan of having stolen their rain.
According to sceptics, cloud seeding is no better than a rain dance. Any weather situation is unique, and it is difficult to tell if the rain falls due to natural processes, or because the clouds have been seeded. But in early 2018, US scientists managed to prove the effect of cloud seeding by means of radar monitoring. The data showed that the clouds which had been seeded with silver iodide produced 1001,000 times more ice crystals than the clouds that had not been manipulated.
Pumping the clouds full of chemicals does not immediately sound very eco-friendly, but according to scientists, cloud seeding has no negative effect on the environment. They have carried out more than 30 studies concerning the effect of cloud seeding on the environment, and no contamination has been spotted.
China’s water crisis evaporates
It remains unclear, when China will seriously begin the major weather experiment, but to many of the 1.3 billion people waiting, the rain cannot come fast enough.
In China, 400 cities lack water, and according to a Greenpeace report, agriculture will shrink 23% by 2050 as a consequence.
According to Chinese meteorologists, the thousands of combustion chambers in the Tibetan Plateau will soon end China's worries. It seems unlikely that such a huge problem can be solved so easily, and there will no doubt be many twists and turns along the way. But, just like water itself, that's life.
Meteorologists frequently seed the clouds of North Dakota, USA, with silver iodide and dry ice from planes.