研究人员在爱达荷州人工播撒云朵来增加降雪

研究人员在爱达荷州人工播撒云朵来增加降雪

On a chilly clear day in January, a team of scientists turned their heads to the sky and watched as snowflakes began to fall above them in western Idaho. There was no snow predicted on the weather reports – well, at least, by meteorologist forecasts.

在1月一个寒冷晴朗的日子里，一组科学家把头转向天空，看着雪花开始在爱达荷州西部飘落。天气预报中没有预测到会下雪——至少气象学家是这样预测的。

This snow was created by scientists firing a series of flares from an aircraft to inject silver iodide (AgI) particles into a natural cloud floating by. The experiment, called SNOWIE (Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment), happened two more times over the course of the month.

科学家们从一架飞机上发射了一系列的照明弹，将碘化银(AgI)粒子注入飘过的天然云层中，形成了这场雪。这个实验被称为SNOWIE(播种和自然地形的冬季云层:爱达荷实验)，在一个月内又发生了两次。

Kristy Hamilton

The team led by the University of Colorado Boulder triggered the snow via a technology called "cloud seeding", a much-discussed, much-debated method of increasing water supply to arid regions. To clarify the many uncertainties of such an approach, the team took to the difficult task of measuring artificially provoked precipitation.

由科罗拉多大学博尔德分校领导的研究小组通过一种被称为“播云”的技术引发了这场雪，这是一种被广泛讨论和争论的增加干旱地区供水的方法。为了澄清这种方法的许多不确定性，该小组承担了测量人工诱发降水的艰巨任务。

The study is the one of the first to "show the entire chain of events during three cases from the time we put the seeding material into the cloud, as it converts supercooled liquid into snow, and how the snow falls onto the ground," said Katja Friedrich, an associate professor at the University of Colorado Boulder, to IFLScience.

这项研究是第一个“展示了从我们把种子材料放入云中，当它把过冷的液体变成雪，以及雪是如何落到地面上，在这三种情况下的整个事件链。”科罗拉多大学博尔德分校的副教授Katja Friedrich对IFLScience说。

In all, the seeding events produced enough water to fill around 282 Olympic-sized swimming pools. That may sound like a lot, and in some ways, it is, however the 2,330 square kilometers (900 square miles) the dusting of snow landed upon came out to be about a tenth of a millimeter deep. The findings are published in the journal Proceedings of the National Academy of Sciences.

总而言之，种子比赛产生的水足以填满282个奥运会标准大小的游泳池。这听起来可能很多，但在某些方面，它是，然而，2330平方公里(900平方英里)的降雪量出来约0.1毫米深。研究结果发表在《美国国家科学院院刊》上。

So how does cloud seeding work? Silver iodide particles are used as "seeds" that are injected into the clouds – the little bits of material provide a surface for water molecules to latch onto and form ice crystals around, eventually producing rain or snow. However, proof that such a method works (and is worth the effort) is controversial. Studies have yielded conflicting or inconclusive results, with specific measurements difficult to attain: Is the additional precipitation natural or man-made? The uncertainties of weather make cloud seeding a less-than-ideal uncontrolled experiment.

那么，人工降雨是如何起作用的呢?碘化银粒子被用作“种子”，被注入云层——这些小块的物质为水分子提供了一个附着的表面，并在周围形成冰晶，最终形成雨或雪。然而，证明这种方法有效(并且值得努力)是有争议的。研究产生了相互矛盾或不确定的结果，很难获得具体的测量:额外的降水是自然的还是人为的?天气的不确定性使播云成为不太理想的不受控制的实验。

The Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment (SNOWIE) project radar dish gets a dusting of ice in 2017. Joshua Aikins

"Previous studies used statistical comparisons between seeded and non-seeded events and times as well as target and control areas – the big caveat here is are the conditions the same? Some studies reported enhancements in snowfall due to cloud seeding that range between 0.5 and 2 mm h-1 but these are only point measurements and we cannot say how much water is being generated over the entire catchment," said Friedrich.

“之前的研究使用了种子和非种子赛事、时间以及目标和控制区域的统计比较——这里需要注意的是，情况是一样的吗?”一些研究报告说，由于人工降雨，降雪量增加了0.5毫米到2毫米，但这些只是点测量，我们不能说整个流域产生了多少水，”弗里德里希说。

However, "This paper quantifies the amount of snow produced over an entire catchment."

然而，“这篇论文量化了整个流域产生的雪量。”

Another question that rises to the surface is whether there are environmental costs of such an inference to natural weather patterns. A previous report suggested that preliminary hazards seem low. Yet this isn’t to say there aren't any, just that the evidence for a definitive answer is not there yet. It's also important to note that the technology is powerless without clouds and their location matters too. Concerns that silver iodide can make people sick have so far shown negligible effects at the levels used to seed clouds.

另一个浮出水面的问题是，这种对自然天气模式的推断是否会造成环境成本。之前的一份报告显示，初步的危险似乎很低。然而，这并不是说没有任何证据，只是没有明确答案的证据。需要注意的是，如果没有云，这项技术是无能为力的，云的位置也很重要。人们担心碘化银会让人生病，但迄今为止，碘化银对云层的影响微乎其微。

Pilots have previously modified weather patterns to stop hail destroying crops in Alberta, Canada. Such measures are becoming more popular, but the research is still limited in what it can say are the final effects. For states such as Idaho and Colorado, rivers that are used as water for districts depend on the amount of snowfall they receive.

飞行员之前已经修改了天气模式，以阻止冰雹破坏加拿大阿尔伯塔省的农作物。这些措施正变得越来越受欢迎，但这项研究的最终效果仍是有限的。对于像爱达荷州和科罗拉多州这样的州来说，作为地区用水的河流取决于它们收到的降雪量。

"The clouds are seeded with silver iodide, which will end up in streams and rivers. In general, the cloud seeding entities have to comply to environmental regulations, like every other company," noted Friedrich. "As far as I know the amount of silver ending up in the ground water is low and the same order of magnitude as the natural silver background concentration. However, this is not my area of expertise."

“这些云被播种了碘化银，碘化银最终会流入小溪和河流。一般来说，云种实体必须遵守环境法规，就像其他公司一样。“据我所知，地下水中的银含量很低，与天然银本底浓度的数量级相同。然而，这不是我的专业领域。”

In addition, "the study only looked at three cases. Water managers want to know how much water is being produced over an entire water year or winter season. That would be the next step that we want to address with numerical modeling."

此外，“这项研究只研究了三个案例。水管理人员想要知道整个水年或冬季生产了多少水。这将是我们想要通过数值模拟解决的下一个步骤。”

Researchers use this truck-mounted radar dish to track and measure cloud seeding events in western Idaho. Joshua Aikins