News / Science & Technology

Study: Jet Traffic Near Airports Can Trigger Snowfalls

Artificially-induced snow creates circular hole in cloud layer

A hole-punch cloud over Alabama
A hole-punch cloud over Alabama

Multimedia

Audio

Scientists have found that aircraft flying through a layer of cold-temperature clouds can trigger a snowfall that normally wouldn’t occur.

The artificially-induced snow creates a great circular hole in the cloud layer. "Hole-punch" clouds are so rare and unique-looking, some witnesses have mistaken them for UFOs.

“Just do a search on hole-punch clouds on the web and you’ll see fabulous examples of what look like layer clouds with circular holes in them,” says Andy Heymsfield, senior scientist at the National Center for Atmospheric Research in Colorado and lead scientist on the study.



Three and a half years ago, he wasn’t attempting to link aircraft to hole-punch clouds. Instead, he and his colleagues were trying to understand how ice crystals form and develop in clouds.

Accidental discovery

“We had a research aircraft equipped with almost every imaginable probe for measuring the structure or the internal properties of these clouds,” he says.

One of these instruments was a cloud radar, a special device that can peer inside clouds just as an x-ray peers inside our body. About six months after their field work, a scientist studying the radar images stumbled across something very interesting, something he couldn’t explain.

"He passed through a very strange band of snow falling to the ground," says Heymsfield. "It was just fairly isolated. He noticed a very narrow line, but a long line, of precipitation that seemed to be coming out from a cloud deck up high."

There were no meteorological reasons why snow would be falling only along a linear path instead of over a wide area. So he turned to the other instruments to explain the phenomenon.

"On the aircraft we had digital photography looking forward and down so I could actually see what looked like snow reaching the ground and what looked like a line - a hole, canal or a channel in the cloud layer above," says Heymsfield.

Mysterious snowfall

The snowfall had hollowed out a long channel in the cloud. But there was still no explanation for what caused the line of snow, although Heymsfield had a hunch.

Reviewing the flightpaths of planes flying in and out of Denver International Airport, he found the snowfall followed the path a  turboprop airplane had flown earlier that day.

“And in natural clouds you can have liquid water at temperatures in clouds down to as far as minus 40 degrees C before the droplets sort of automatically freeze,” he says.

In perfect conditions, aircraft can cool a cloud enough to generate those ice crystals.

The spinning propeller expands and cools the air behind it by as much as 30 degrees centigrade. Similar cooling occurs with jet aircraft. The pressure reduction over the wing which gives it lift also causes the air to expand and cool.

“Ice crystals upon which the ice can grow are introduced into a cloud, then the ice crystals will grow, the droplets will evaporate and you can generate snow.”

Airport connection

The next question was: can this happen around airports where there are a lot of commercial jet flights?  

“We used satellite imagery to document that around airports with heavily trafficked areas conditions are just right fairly commonly- a winter month, maybe 10 or 15 percent of the time," he says. "When it does happen, ice crystals would be generated upwind of an airport, which could then drift over the airport and lead to more deicing operation”

Heymsfield says this phenomenon is not likely to affect global climate. Fellow cloud scientist, Patrick Chuang, agrees. But the associate professor of Earth and Planetary Sciences at the University of California, Santa Cruz, says the effect may skew climate records.

“I think the importance is in the fact that we really rely on airports to provide long-term records of weather, which then are used for things like climate change detection and just understanding how climate is changing," says Chuang. "It’s not like any cloud is conducive to this. I think it’s still not going to be a very commonplace event.”

You May Like

How to Safeguard Your Mobile Privacy

As the digital world becomes more mobile, so too do concerns about eroding privacy and increased hacking More

'Desert Dancer' Chronicles Iranian Underground Dance Troupe

Film by Richard Raymond is based on true story of Afshin Ghaffarian and his friends More

Audio Top 5 Songs for Week Ending May 23

This week's lineup can be summed up like this: 'It's The Same Old Song' - but they're great songs - featuring Walk The Moon, The Weeknd, Wiz Khalifa and Charlie Puth More

This forum has been closed.
Comments
     
There are no comments in this forum. Be first and add one

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Female American Soldiers: Healing Through Filmmakingi
X
Bernard Shusman
May 24, 2015 2:55 PM
According to the United States Defense Department, there are more than 200-thousand women serving in the U.S. Armed Forces.  Like their male counterparts, females have experiences that can be very traumatic.  VOA's Bernard Shusman tells us about a program that is helping some American women in the military heal through filmmaking.
Video

Video Female American Soldiers: Healing Through Filmmaking

According to the United States Defense Department, there are more than 200-thousand women serving in the U.S. Armed Forces.  Like their male counterparts, females have experiences that can be very traumatic.  VOA's Bernard Shusman tells us about a program that is helping some American women in the military heal through filmmaking.
Video

Video Rolling Thunder Run Reveals Changed Attitudes Towards Vietnam War

For many US war veterans, the Memorial Day holiday is an opportunity to look back at a divisive conflict in the nation’s history and to remember those who did not make it home.
Video

Video Millions Flock to Ethiopia Polls

Millions of Ethiopians cast their votes Sunday in the first national election since the 2012 death of longtime leader Meles Zenawi. Mr. Meles' party, the Ethiopian People's Revolutionary Democratic Front, is almost certain of victory again. VOA's Anita Powell reports from Addis Ababa.
Video

Video Scientists Testing Space Propulsion by Light

Can the sun - the heart of our solar system - power a spacecraft to the edge of our solar system? The answer may come from a just-launched small satellite designed to test the efficiency of solar sail propulsion. Once deployed, its large sail will catch the so-called solar wind and slowly reach what scientists hope to be substantial speed. VOA’s George Putic reports.
Video

Video FIFA Trains Somali Referees

As stability returns to the once lawless nation of Somalia, the world football governing body, FIFA, is helping to rebuild the country’s sport sector by training referees as well as its young footballers. Abdulaziz Billow has more from Mogadishu.
Video

Video With US Child Obesity Rates on the Rise, Program Promotes Health Eating

In its fifth year, FoodCorps puts more than 180 young Americans into 500 schools across the United States, where they focus on teaching students about nutrition, engaging them with hands-on activities, and improving their access to healthy foods whether in the cafeteria or the greater community. Aru Pande has more.
Video

Video Virginia Neighborhood Draws People to Nostalgic Main Street

In the U.S., people used to grow up in small towns with a main street lined by family-owned shops and restaurants. Today, however, many main streets are worn down and empty because shoppers have been lured away by shopping malls. But in the Del Ray neighborhood of Alexandria, Virginia, main street is thriving. VOA’s Deborah Block reports it has a nostalgic feel with its small restaurants and unique stores.
Video

Video Effort Underway to Limit Damage from California Oil Spill

Cleanup crews are working around the clock to remove oil from the waters off the coastal city of Santa Barbara, in California. About 380,000 liters of oil may have leaked out before a rupture in an onshore, underground pipeline was discovered Tuesday. The environmental disaster hit the popular West Coast resort area before the Memorial Day weekend. VOA's Zlatica Hoke reports investigators have yet to determine what caused the incident.

VOA Blogs