美国国家公共电台 NPR--Western wildfires are making far away storms more dangerous

Western wildfires are making far away storms more dangerous

Transcript¹

In late July of 2018, massive wildfires blazed across Northern California. At the same time in Colorado, weather alerts went out warning of heavy thunderstorms and baseball-sized hail.

The two disasters were separated by a thousand miles, but scientists are now finding they're connected.

The massive clouds of smoke and heat that rise out of Western wildfires are having far-reaching effects across the country, even beyond hazy² skies. That summer, the smoke blew to the Central U.S., where it ran headlong into summertime thunderstorms that were already forming.

The collision made those storms even more extreme, boosting the rainfall and hail by more than 30 percent, according to a new study in the Proceedings³ of the National Academy of Sciences.

"It's surprising to many people, probably," says Jiwen Fan, Laboratory Fellow at the Department of Energy's Pacific Northwest National Laboratory and an author of the study. "I really wanted to look at if there's any connections between them."

Understanding the effects of wildfires on weather patterns far downstream could help improve forecasts in those areas. In the Central U.S., extreme summer storms can pose a dangerous threat, often doing millions of dollars in damage.

"Scientists are showing that things are really connected to each other," says Danielle Touma, a postdoctoral researcher at the National Center for Atmospheric⁴ Research, who was not involved in the study. "And we can't just think about where we live, but we have to think about what's happening in other parts of the world."

Smoke helps fuel extreme rainfall

While it may seem like raindrops simply pour out of clouds, those drops won't form without a seed to get them started. Raindrops need microscopic⁵ particles, known as aerosols⁶, which can be dust, soot⁷, or even microbes, floating in the air.

"Lots of people do not realize, before rain, you have to have the tiny particles," Fan says. "They're tiny particles you cannot see with the bare eye."

The particles give water something to condense onto, eventually getting heavy enough to fall to the ground. In 2018, as the Carr Fire and Mendocino Complex burned in California, massive amounts of particles floated east across the Rockies, where they collided with large thunderstorms.

More particles created the conditions for more raindrops, as well as hail, which occurs when powerful storms lift particles high into the cloud and water freezes on them. Running complex computer models, Fan and colleagues found that the Western wildfires boosted heavy rainfall in the storms by 34 percent and large hail by 38 percent.

The heat released from wildfires also played a major role, since it can strengthen the winds that blow to the Central U.S.. Those winds picked up extra moisture on the way, providing more fuel for the thunderstorms and strengthening the intense dynamics⁸ inside the storms themselves. In the July 2018 storms, the winds in Colorado topped 100 miles per hour.

"These kinds of things can cause hail damage or flooding, depending on where the precipitation is falling," Sonia M. Kreidenweis, professor of atmospheric science at Colorado State University. "If the Central U.S. wasn't already set up to have a storm, it might not have the same kind of impact."

Improving weather forecasts for extreme storms

Historically, the West's fall fire season didn't overlap⁹ much with the summer thunderstorm season in Central U.S. states. But with climate change creating drier, hotter conditions for wildfires, that overlap could become more common, since destructive wildfires are happening earlier in the year.

Understanding this long-range influence of wildfires could help improve weather forecasts, giving communities in the Central U.S. more accurate warnings when destructive hail and rain are on the way.

"If they know that California or Oregon are having an above average wildfire season, they might want to be on the lookout¹⁰ for more severe storms coming their way," Touma says.

1 transcript   

n.抄本，誊本，副本，肄业证书

参考例句：

• A transcript of the tapes was presented as evidence in court.一份录音带的文字本作为证据被呈交法庭。
• They wouldn't let me have a transcript of the interview.他们拒绝给我一份采访的文字整理稿。

2 hazy   

adj.有薄雾的，朦胧的；不肯定的，模糊的

参考例句：

• We couldn't see far because it was so hazy.雾气蒙蒙妨碍了我们的视线。
• I have a hazy memory of those early years.对那些早先的岁月我有着朦胧的记忆。

3 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

4 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。

5 microscopic   

adj.微小的，细微的，极小的，显微的

参考例句：

• It's impossible to read his microscopic handwriting.不可能看清他那极小的书写字迹。
• A plant's lungs are the microscopic pores in its leaves.植物的肺就是其叶片上微细的气孔。

6 aerosols   

n.气溶胶( aerosol的名词复数 )；喷雾剂；（气体中的）浮粒；喷雾器

参考例句：

• Aerosols are present throughout the atmosphere. 气溶胶存在于整个大气层。 来自辞典例句
• Deodorants are available as aerosols or roll-ons. 除臭剂有喷雾装或滚抹装。 来自辞典例句

7 soot   

n.煤烟，烟尘；vt.熏以煤烟

参考例句：

• Soot is the product of the imperfect combustion of fuel.煤烟是燃料不完全燃烧的产物。
• The chimney was choked with soot.烟囱被煤灰堵塞了。

8 dynamics   

n.力学，动力学，动力，原动力；动态

参考例句：

• In order to succeed,you must master complicated knowledge of dynamics.要取得胜利，你必须掌握很复杂的动力学知识。
• Dynamics is a discipline that cannot be mastered without extensive practice.动力学是一门不做大量习题就不能掌握的学科。

9 overlap   

v.重叠，与…交叠；n.重叠

参考例句：

• The overlap between the jacket and the trousers is not good.夹克和裤子重叠的部分不好看。
• Tiles overlap each other.屋瓦相互叠盖。

10 lookout   

n.注意，前途，瞭望台

参考例句：

• You can see everything around from the lookout.从了望台上你可以看清周围的一切。
• It's a bad lookout for the company if interest rates don't come down.如果利率降不下来，公司的前景可就不妙了。