(by Jane Macartney, London’s timesonline.co.uk) BEIJING — Cloud-seeding by Chinese meteorologists has led to the earliest snow blizzard in Beijing for two decades.
The 11-hour snowfall, which could be the heaviest in a decade, brought the capital to a halt and hundreds of flights were delayed.
China’s meteorologists are desperate to alleviate a prolonged drought gripping swaths of the country. Zhang Qiang, head of the Beijing Weather Modification Office, said: “We won’t miss any opportunity of artificial precipitation since Beijing is suffering from a lingering drought.”
With forecasts for precipitation and a sharp drop in temperatures at the weekend, the meteorologists saw their chance. From 8pm on Saturday they fired 186 silver iodide capsules into clouds heavy with snow to help the precipitation. The result was snow that fell for 11 hours from the early hours of Sunday until mid-afternoon.
The cloud-seeding expanded the natural snowfall by 16 million tonnes, officials said. It was not clear how they calculated that figure. Beijing is becoming increasingly sophisticated in the use of cloud-seeding. Officials fired off 1,110 silver iodide rockets before the Olympic Games opening ceremony on August 8 last year to ensure clear skies on the night.
On Coal Hill, a scenic spot in the heart of Beijing that overlooks the Forbidden City, officials reported 25mm (0.9in) of snow. Temperatures plummeted by as much as 20C from Saturday to a low of about minus 9C late on Sunday as the clouds cleared and winds blew over the city from Siberia.
Snow has not fallen so early in the season in Beijing since 1987, officials said. The earliest recorded snowfall in the city was on October 26, 1960. Beijing is accustomed to freezing winters but snow rarely falls more than three or four times each winter.
Reprinted here for educational purposes only. May not be reproduced on other websites without permission from The Times Online. Visit the website at timesonline.co.uk.
1. Define cloud-seeding and silver iodide.
2. Why did Chinese meteorologists seed clouds above Beijing?
3. What was the result of the cloud-seeding over Beijing?
4. How did Chinese officials use cloud-seeding prior to the Olympic Games opening ceremony in August?
5. How often does snow fall in Beijing?
6. Read the “Background” and information under “Resources.” Do you agree with the practice of cloud-seeding to end a drought and/or to ensure good weather for an event? Explain your answer.
ON THE PRACTICE OF CLOUD-SEEDING:
- The United States began weather control research in 1946. Currently, some states use cloud-seeding programs in an attempt to increase precipitation levels or prevent crop-damaging hail. An eight-year experiment in Texas and Oklahoma, conducted over 5,000 square miles (12,950 square kilometers), showed that cloud seeding increased rainfall, cloud height, length of storms and the area in which rain fell [source: Eckhardt]. Even so, enthusiasm for cloud seeding in the U.S. has dried up since the early 1970s, when federal funding was about $19 million a year [source: Cotton, Engber]. Now states have to kick in the dough if they want to try ruling the skies.
- Internationally, Russia, Israel, Thailand, South Africa and Caribbean nations have all tried their hand at cloud seeding, 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.
- Despite some successful tests, cloud seeding still has many problems. The fundamental concern is:
Does it work? It may be a chicken-and-egg conundrum — would it have rained in a given area without the use of cloud seeding, and would it have rained less? Cloud seeding also depends heavily on environmental conditions like temperature and cloud composition.
- In 2003, the United States National Academy of Sciences declared that 30 years of studies had not produced “convincing” evidence that weather modification works [source: Associated Press]. On the other hand, the American Meteorological Society claims that some studies on cloud seeding show a 10 percent increase in rain volume [source: Eckhardt].
- Cloud seeding is quite expensive, though potentially cheaper than other projects, like diverting rivers, building new canals or improving irrigation systems. Then again, 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 effort better spent tackling the causes of global warming?
- Despite reassurances from cloud-seeding companies, concerns also remain about exposure to silver iodide toxicity and soil contamination. …cloud seeding has strong supporters, but it remains controversial.
- 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 [source: Things Asian]. The government plans to produce 1.7 trillion cubic feet (50 billion cubic meters) of rain a year through the practice [source: Aiyar]. … (from science.howstuffworks.com/cloud-seeding2.htm)
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