New Research Confirms Cloud Seeding Can Produce Snowfall
2020-02-27
LRC
TXT
大字
小字
滚动
全页
1Scientists say they used new measuring methods to confirm that cloud seeding can produce snowfall under the right conditions.
2Researchers used radar and other instruments to measure snowfall levels during experiments carried out in 2017 in the American state of Idaho.
3The experiments involved scientists from several American universities, as well as the U.S. National Center for Atmospheric Research, or NCAR.
4A study reporting the results was recently published in Proceedings of the National Academy of Sciences.
5Cloud seeding has been tested in parts of the United States since the 1940s.
6It involves injecting various substances into clouds to produce precipitation - rain, snow or ice that falls to the ground.
7The process can cause ice to form and build up inside the clouds until it falls.
8Some western U.S. states - including Idaho and Colorado - have increased cloud seeding in recent years to help meet a growing water demand.
9Until now, however, it has been difficult for scientists to measure the effectiveness of the process.
10Researchers have mainly used instruments to compare the amount of precipitation from seeded clouds to similar clouds that were not seeded.
11But such studies have brought mixed results.
12This is partly because many elements influence natural precipitation, which makes it hard to narrow down exact cause and effect results.
13The research operation over western Idaho was called SNOWIE.
14It involved shooting small amounts of a chemical compound called silver iodide from an airplane into clouds.
15The chemical can cause water in the clouds to freeze into ice and then fall as snow.
16In the new experiments, the scientists used radar equipment together with precipitation measuring instruments to collect data.
17The use of airborne and ground-based radars permitted the team "to observe the entire process and compare the side-by-side seeded and unseeded areas," the NCAR said in a statement.
18In at least three cases, "the seeding measurably boosted the snowfall across the targeted watershed," the statement said.
19In some areas, the cloud seeding created new snowfall where no natural snow existed.
20One cloud seeding flight resulted in precipitation that produced snowfall for about 67 minutes.
21The researchers estimated the three cases described in the study produced a combined precipitation total that could fill about 285 Olympic-sized swimming pools.
22The researchers also used computer modeling to study precipitation measurements during simulated weather activity.
23The scientists say they hope to use the real results from the new experiments to improve future computer modeling predictions.
24Sarah Tessendorf is a scientist at NCAR. She helped lead the experiments.
25She called the results a "revelation" to helping understand the effectiveness of cloud seeding technology.
26But Tessendorf noted that the experiments also demonstrated that successful cloud seeding operations are dependent on certain conditions.
27There must be existing clouds to seed.
28The results are also dependent on local atmospheric conditions, such as temperature and wind.
29Tessendorf said additional research would be required to study the long-term costs of major cloud seeding operations.
30"The seeding produces ice and that ice can form snow, but is it enough additional snow to make it cost-effective?" she asked.
31While future experiments will seek to address those bigger questions, "we still have plenty of work to do to get there," she added.
32I'm Bryan Lynn.
1Scientists say they used new measuring methods to confirm that cloud seeding can produce snowfall under the right conditions. 2Researchers used radar and other instruments to measure snowfall levels during experiments carried out in 2017 in the American state of Idaho. 3The experiments involved scientists from several American universities, as well as the U.S. National Center for Atmospheric Research, or NCAR. A study reporting the results was recently published in Proceedings of the National Academy of Sciences. 4Cloud seeding has been tested in parts of the United States since the 1940s. It involves injecting various substances into clouds to produce precipitation - rain, snow or ice that falls to the ground. The process can cause ice to form and build up inside the clouds until it falls. 5Some western U.S. states - including Idaho and Colorado - have increased cloud seeding in recent years to help meet a growing water demand. Until now, however, it has been difficult for scientists to measure the effectiveness of the process. 6Researchers have mainly used instruments to compare the amount of precipitation from seeded clouds to similar clouds that were not seeded. But such studies have brought mixed results. This is partly because many elements influence natural precipitation, which makes it hard to narrow down exact cause and effect results. 7The research operation over western Idaho was called SNOWIE. It involved shooting small amounts of a chemical compound called silver iodide from an airplane into clouds. The chemical can cause water in the clouds to freeze into ice and then fall as snow. 8In the new experiments, the scientists used radar equipment together with precipitation measuring instruments to collect data. The use of airborne and ground-based radars permitted the team "to observe the entire process and compare the side-by-side seeded and unseeded areas," the NCAR said in a statement. 9In at least three cases, "the seeding measurably boosted the snowfall across the targeted watershed," the statement said. In some areas, the cloud seeding created new snowfall where no natural snow existed. One cloud seeding flight resulted in precipitation that produced snowfall for about 67 minutes. 10The researchers estimated the three cases described in the study produced a combined precipitation total that could fill about 285 Olympic-sized swimming pools. 11The researchers also used computer modeling to study precipitation measurements during simulated weather activity. The scientists say they hope to use the real results from the new experiments to improve future computer modeling predictions. 12Sarah Tessendorf is a scientist at NCAR. She helped lead the experiments. She called the results a "revelation" to helping understand the effectiveness of cloud seeding technology. 13But Tessendorf noted that the experiments also demonstrated that successful cloud seeding operations are dependent on certain conditions. There must be existing clouds to seed. The results are also dependent on local atmospheric conditions, such as temperature and wind. 14Tessendorf said additional research would be required to study the long-term costs of major cloud seeding operations. "The seeding produces ice and that ice can form snow, but is it enough additional snow to make it cost-effective?" she asked. 15While future experiments will seek to address those bigger questions, "we still have plenty of work to do to get there," she added. 16I'm Bryan Lynn. 17Bryan Lynn wrote this story for VOA Learning English, based on reports from NCAR, the University of Colorado at Boulder, the University of Illinois at Urbana-Champaign and the University of Wyoming. Ashley Thompson was the editor. 18We want to hear from you. Write to us in the Comments section, and visit our Facebook page. 19_______________________________________________________________ 20Words in This Story 21narrow down - phrasal verb. to make a group or list smaller 22data - n. information or facts about something 23boost - v. to increase of improve something 24watershed - n. an area of land that separates waters flowing to different rivers, basins, or seas 25simulated - adj. something made to look or behave like something real but which is not 26revelation - n. an extremely pleasant surprise 27certain - adj. completely sure of something