Scientists say they used new measuring methods to confirm that cloud seeding can produce snowfall under the right conditions.

科学家们说，他们使用了新的测量方法，以证实播云可以在适当的条件下产生降雪。

Researchers used radar and other instruments to measure snowfall levels during experiments carried out in 2017 in the American state of Idaho.

在2017年在美国爱达荷州进行的实验中，研究人员使用雷达和其他仪器来测量降雪量。

The experiments involved scientists from several American universities,

参与这项实验的科学家来自美国几所大学

as well as the U.S. National Center for Atmospheric Research, or NCAR.

以及美国国家大气研究中心(简称NCAR)。

A study reporting the results was recently published in Proceedings of the National Academy of Sciences.

一份研究结果报告最近发表在《美国国家科学院院刊》上。

Cloud seeding has been tested in parts of the United States since the 1940s.

自20世纪40年代以来，美国部分地区一直在进行播云试验。

It involves injecting various substances into clouds to produce precipitation –

这包括向云层中注入各种不同物质以产生降水—

rain, snow or ice that falls to the ground.

降雨、降雪或落到地面的冰。

The process can cause ice to form and build up inside the clouds until it falls.

这个过程会导致冰在云层中形成并积聚，然后落到地面上。

Some western U.S. states – including Idaho and Colorado –

美国西部的一些州，包括爱达荷州和科罗拉多州在内，

have increased cloud seeding in recent years to help meet a growing water demand.

近年来增加了播云次数，以帮助满足日益增长的水需求。

Until now, however, it has been difficult for scientists to measure the effectiveness of the process.

然而，到目前为止，科学家们还很难衡量这一过程的有效性。

Researchers have mainly used instruments

研究人员主要使用仪器

to compare the amount of precipitation from seeded clouds to similar clouds that were not seeded.

来比较播种云和未播种云的降水量。

But such studies have brought mixed results.

但这类研究的结果收效不一。

This is partly because many elements influence natural precipitation,

部分原因是因为影响自然降水的因素很多，

which makes it hard to narrow down exact cause and effect results.

这导致很难缩小确切原因和影响结果的范围。

The research operation over western Idaho was called SNOWIE.

爱达荷州西部地区开展的研究项目名为SNOWIE。

It involved shooting small amounts of a chemical compound called silver iodide from an airplane into clouds.

该项目包括从飞机上向云层发射少量的化合物碘化银。

The chemical can cause water in the clouds to freeze into ice and then fall as snow.

这种化学物质会使云层中的水冻结成冰，然后像雪一样落下。

In the new experiments, the scientists used radar equipment together with precipitation measuring instruments to collect data.

在新的实验中，科学家们使用雷达设备和降水测量仪器来收集数据。

The use of airborne and ground-based radars permitted the team

美国国家大气研究中心在一份声明中表示，通过使用机载雷达和地基雷达，

"to observe the entire process and compare the side-by-side seeded and unseeded areas," the NCAR said in a statement.

研究团队可以“观察整个过程并且比较并排播种区和非播种区”。

In at least three cases, "the seeding measurably boosted the snowfall across the targeted watershed," the statement said.

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”。

In some areas, the cloud seeding created new snowfall where no natural snow existed.

在一些地区，播云在没有自然降雪的地方带来了新的降雪。

One cloud seeding flight resulted in precipitation that produced snowfall for about 67 minutes.

一次播云飞行产生了降水，降雪持续了约67分钟。

The researchers estimated the three cases described in the study

研究人员估计，研究中所描述的三种情况

produced a combined precipitation total that could fill about 285 Olympic-sized swimming pools.

产生的总降水量可填满约285个奥运会标准大小的游泳池。

The researchers also used computer modeling to study precipitation measurements during simulated weather activity.

研究人员还使用计算机建模来研究模拟天气活动期间的降水量测量。

The scientists say they hope to use the real results from the new experiments to improve future computer modeling predictions.

科学家们表示，他们希望利用新实验中的真实结果来改进未来的计算机模型预测。

Sarah Tessendorf is a scientist at NCAR.

萨拉·特森多夫是美国国家大气研究中心的科学家。

She helped lead the experiments.

她帮助领导了实验。

She called the results a "revelation" to helping understand the effectiveness of cloud seeding technology.

她称结果是“启示”，有助于理解播云技术的效果。

But Tessendorf noted that the experiments also demonstrated

但是，特森多夫同时指出，实验还表明，

that successful cloud seeding operations are dependent on certain conditions.

成功的播云作业取决于特定的条件。

There must be existing clouds to seed.

必须有用来播种的云。

The results are also dependent on local atmospheric conditions, such as temperature and wind.

结果还取决于当地的大气条件，比如温度和风力。

Tessendorf said additional research would be required to study the long-term costs of major cloud seeding operations.

特森多夫说，需要进行更多的研究来调查主要的播云作业的长期成本。

"The seeding produces ice and that ice can form snow,

她问道:“播种会产生冰，而冰可以形成雪，

but is it enough additional snow to make it cost-effective?" she asked.

但是，是否有足够的额外雪来足以使其符合成本效益？”

While future experiments will seek to address those bigger questions,

虽然未来的实验将设法解决这些更大的问题，

"we still have plenty of work to do to get there," she added.

但在实现目标之前我们仍有大量工作要做。”，她补充说。

I'm Bryan Lynn.

布莱恩·林恩为您播报。