(单词翻译:单击)
听力文本
New Research Confirms Cloud Seeding Can Produce Snowfall
Scientists say they used new measuring methods to confirm that cloud seeding can produce snowfall under the right conditions.
Researchers used radar and other instruments to measure snowfall levels during experiments carried out in 2017 in the American state of Idaho.
The 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.
Cloud 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.
Some 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.
Researchers 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.
The 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.
In 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.
In 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.
The researchers estimated the three cases described in the study produced a combined precipitation total that could fill about 285 Olympic-sized swimming pools.
The 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.
Sarah 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.
But 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.
Tessendorf 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.
While future experiments will seek to address those bigger questions, "we still have plenty of work to do to get there," she added.
I'm Bryan Lynn.
重点解析
重点讲解：
1. build up （使）积聚；（使）逐渐增加；
Always using the same shampoo means that a residue can build up on the hair.
总是用同一种洗发水就意味着某种残留物会在头发上越积越多。
2. narrow down 缩减；压缩；减小；
What's happened is that the new results narrow down the possibilities.
现有的情况是，新的结果缩小了可能性的范围。
3. result in 导致；引起；造成；
Fifty per cent of road accidents result in head injuries.
50％的道路交通事故都会导致头部损伤。
4. be dependent on 取决（于…）的；有赖（于…）的；
The local economy is overwhelmingly dependent on oil and gas extraction.
当地经济过于依赖石油和天然气的开采。
参考译文
新研究证实播云会产生降雪
科学家表示，他们使用了新的测量方法，证实播云可以在适当的条件下产生降雪。
在2017年于美国爱达荷州进行的实验中，研究人员用雷达和其他仪器测量了降雪量。
参与这项实验的科学家来自美国多所大学以及美国国家大气研究中心（简称NCAR）。一份研究结果报告于近期发表在《美国国家科学院院刊》上。
自上世纪40年代以来，美国部分地区一直在进行播云试验。这包括向云层中注入不同物质以产生降水——降雨、降雪或落在地面上的冰。这一过程会导致冰在云层中形成并积聚，然后落到地面上。
包括爱达荷州和科罗拉多州在内，美国西部一些州最近几年增加了播云次数，以帮助满足日益增长的水需求。然而，直到目前，科学家仍然难以测量这一过程的效果。
研究人员主要用仪器来比较播种云和未播种云的降水量。但这类研究的结果收效不一。部分原因在于影响自然降水的因素很多，这导致很难缩小确切原因和影响结果的范围。
爱达荷州西部地区开展的研究项目名为SNOWIE。该项目包括从飞机上向云层发射少量的化合物碘化银。这种化学物质会使云层中的水冻结成冰，之后像雪一样落下。
在新实验中，科学家用雷达设备和降水测量仪器来收集数据。美国国家大气研究中心在声明中表示，使用机载雷达和地基雷达令团队得以“观察整个过程并比较并排播种区和非播种区”。
声明表示，在至少三种情况下，“播种显著地促进了整个目标流域的降雪。”在部分地区，播云带来了新的降雪，那里并没有自然降雪。一次播云飞行产生了降水，降雪持续了约67分钟。
研究人员估计，研究中所描述三种情况产生的总降水量可填满大约285个奥运会规格的游泳池。
研究人员还用计算机模型来研究模拟天气活动期间的降水量测量。科学家表示，他们希望用新实验中的真实结果来改进未来的计算机模型预测。
萨拉·泰森多夫是美国国家大气研究中心的科学家。她帮助领导了这一实验。她称结果是“启示”，有助于理解播云技术的效果。
但泰森多夫同时指出，实验也证明，成功的播云作业取决于某些条件。必须有用来播种的云。实验结果还取决于当地的大气条件，比如温度和风力。
泰森多夫表示，需要进行更多研究来调查主要播云作业的长期成本。她问道：“播种会产生冰，而冰可以形成雪，那更多的雪是否足以使其符合成本效益？”
她补充说，虽然未来的实验将设法解决这些更大的问题，“但在实现目标之前我们仍有大量工作要做。”
布莱恩·林恩报道。
译文为可可英语翻译，未经授权请勿转载！
