研究人員在愛達荷州人工播撒云朵來增加降雪

研究人員在愛達荷州人工播撒云朵來增加降雪

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月一個寒冷晴朗的日子里，一組科學家把頭轉向天空，看著雪花開始在愛達荷州西部飄落。天氣預報中沒有預測到會下雪——至少氣象學家是這樣預測的。

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.

科學家們從一架飛機上發(fā)射了一系列的照明彈，將碘化銀(AgI)粒子注入飄過的天然云層中，形成了這場雪。這個實驗被稱為SNOWIE(播種和自然地形的冬季云層:愛達荷實驗)，在一個月內(nèi)又發(fā)生了兩次。

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.

由科羅拉多大學博爾德分校領導的研究小組通過一種被稱為“播云”的技術引發(fā)了這場雪，這是一種被廣泛討論和爭論的增加干旱地區(qū)供水的方法。為了澄清這種方法的許多不確定性，該小組承擔了測量人工誘發(fā)降水的艱巨任務。

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.

這項研究是第一個“展示了從我們把種子材料放入云中，當它把過冷的液體變成雪，以及雪是如何落到地面上，在這三種情況下的整個事件鏈。”科羅拉多大學博爾德分校的副教授Katja Friedrich對IFLScience說。

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.

總而言之，種子比賽產(chǎn)生的水足以填滿282個奧運會標準大小的游泳池。這聽起來可能很多，但在某些方面，它是，然而，2330平方公里(900平方英里)的降雪量出來約0.1毫米深。研究結果發(fā)表在《美國國家科學院院刊》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?碘化銀粒子被用作“種子”，被注入云層——這些小塊的物質(zhì)為水分子提供了一個附著的表面，并在周圍形成冰晶，最終形成雨或雪。然而，證明這種方法有效(并且值得努力)是有爭議的。研究產(chǎn)生了相互矛盾或不確定的結果，很難獲得具體的測量:額外的降水是自然的還是人為的?天氣的不確定性使播云成為不太理想的不受控制的實驗。

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.

“之前的研究使用了種子和非種子賽事、時間以及目標和控制區(qū)域的統(tǒng)計比較——這里需要注意的是，情況是一樣的嗎?”一些研究報告說，由于人工降雨，降雪量增加了0.5毫米到2毫米，但這些只是點測量，我們不能說整個流域產(chǎn)生了多少水，”弗里德里希說。

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

然而，“這篇論文量化了整個流域產(chǎn)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.

另一個浮出水面的問題是，這種對自然天氣模式的推斷是否會造成環(huán)境成本。之前的一份報告顯示，初步的危險似乎很低。然而，這并不是說沒有任何證據(jù)，只是沒有明確答案的證據(jù)。需要注意的是，如果沒有云，這項技術是無能為力的，云的位置也很重要。人們擔心碘化銀會讓人生病，但迄今為止，碘化銀對云層的影響微乎其微。

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.

飛行員之前已經(jīng)修改了天氣模式，以阻止冰雹破壞加拿大阿爾伯塔省的農(nóng)作物。這些措施正變得越來越受歡迎，但這項研究的最終效果仍是有限的。對于像愛達荷州和科羅拉多州這樣的州來說，作為地區(qū)用水的河流取決于它們收到的降雪量。

"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."

“這些云被播種了碘化銀，碘化銀最終會流入小溪和河流。一般來說，云種實體必須遵守環(huán)境法規(guī)，就像其他公司一樣。“據(jù)我所知，地下水中的銀含量很低，與天然銀本底濃度的數(shù)量級相同。然而，這不是我的專業(yè)領域。”

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，“這項研究只研究了三個案例。水管理人員想要知道整個水年或冬季生產(chǎn)了多少水。這將是我們想要通過數(shù)值模擬解決的下一個步驟。”

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