How Cirrus Clouds Form — And Why It Matters
May 15, 2012, Ormond Beach, Florida. Photo by
Oct. 2, 2012 --
NASA's Global Precipitation Measurement satellite mission is working to understanding extreme weather with photos of rain and snow worldwide every three hours. But how do these storms look on the ground? NASA's GPM extreme weather photo contest highlights the beauty and ferocity seen first hand from storm-chasers before they duck for cover. Here are NASA's top five picks from over 100 submissions. This photo by Jason Weingart, a photography student at the University of Central Florida, shows a Volusia County lifeguard signaling to surfers at Ormond Beach, Fla., that it is time to exit the water. "The storm actually pushed back on shore as it moved south, and then became strong enough for tornado warnings on three separate occasions. I saw a large wall cloud, another spectacular shelf cloud, and some very tight rotation in the couple hours I stuck with the storm after I left the beach in Ormond," wrote Weingart. NASA Fun Fact: "A shelf cloud is a type of arcus cloud with a wedge shape. It is a low level, horizontal cloud formation usually associated with the leading edge of thunderstorms. The leading (outer) part of the shelf cloud appears smooth due to rising cloud motions, while the underside often appears jagged and wind-torn."
May 22, 2011 Dane County, Wisconsin. Photo by
Atmospheric scientist Grant Petty of the University of Wisconsin - Madison, was with a photography club on a farm in Dane County when he saw this thunderstorm building several miles to the east. "The storm cell dropped 1-3/4 inch hail near Sun Prairie. Fall streaks barely visible under the right side of the anvil may in fact be the falling hail,” he said.
PHOTOS: Sun Dogs, Halos, and Double Rainbows
July 5, 2011 Maricopa, Arizona. Photo by Megg
“This photo was taken in a wash that runs through my neighborhood in Maricopa, AZ. The wash runs north/south through the neighborhood and the haboob (type of intense dust storm) was rolling in from the east," reported photographer Meggan Wood. "I saw the wall of dust coming and quickly drove to the wash to get a good wide-open view of the height of the dust looming over the houses. I barely had time to get back to my car before it hit and I was engulfed! The darkness was surprising but it only lasted about 10-15 minutes before it thinned out enough to where I could drive back home, only about 2 minutes away. This was the giant haboob that made national news when it rolled through and entirely covered all of Phoenix and some surrounding cities. Maricopa is about a half-hour drive south of the Phoenix Sky Harbor airport."
PHOTOS: After the Dust Settles
September 1, 2012 Arlington, Virginia, lookin
Journalist Brian Allen with the Voice of America was at home in Arlington, Va., when this storm rolled over Washington. "The storm that blew through started off with an incredible amount of lightning and then dumped a significant amount of rain in a short amount of time -- on the other side of the river. DC got drenched and Arlington didn't see a drop,” he reported.
NEWS: Lightning Still Largely a Mystery
May 30, 2012 Kechi, Kansas. Photo by Brian Jo
Writer and photographer Brian Johnson is a also an avid storm-chaser for several Kansas radio stations. “As a large squall line moved through the area. The National Weather Service had warned about a large scale Derecho forming and moving through," he wrote. "This spawned a couple brief severe thunderstorms that dumped hail on rush hour traffic before the main line moved in. As the bigger storm moved into the Wichita area, reports were coming in of 70 mph winds and hail. There is an open farm field roughly two miles from my house that I shot lightning on the previous night. I sat there for about 20 minutes before this large squall line pushed through the clouds. I was hit with a pretty good gust front as it got closer, but as the winds increased, I decided to get to shelter. This photo was one of the last ones I took." Read more about Johnson's storm-chasing adventure here:
NEWS: Photos Catch Monster Storm's Approach: Big Pics
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Give the upper atmosphere dust, and it will make cirrus clouds.
It has long been a mystery exactly what causes the formation of cirrus clouds, the wispy billows of ice that can be seen high in the sky. But new research, detailed in the May 9 issue of the journal Science, finds that the clouds condense and freeze, or nucleate, on very specific mineral and metal particles high in the atmosphere. That makes cirrus clouds unique: Most other clouds form primarily by condensing onto organic particles, said study author Dan Cziczo, an atmospheric chemist at the Massachusetts Institute of Technology.
It's important to know how these clouds form, as they can cover up to 30 percent of the Earth's atmosphere at any given time, and have a big effect on the climate, Cziczo told OurAmazingPlanet.
Clouds and climate
In fact, clouds have about 10 times the impact on climate that man-made greenhouse-gas emissions do, said Brian Toon, a researcher at the University of Colorado at Boulder who wasn't involved in the study. "The largest uncertainty in understanding climate change is understanding clouds, since they are so much more important," he said. (The Reality of Climate Change: 10 Myths Busted)
The new study shows, however, that humans actually impact the formation of cirrus clouds (just as climate change affects cloud formation and vice versa, in little-understood ways), by sampling the ice crystals making up the clouds and seeing what particles they formed on. Although mineral particles have always found their way into the upper atmosphere, where cirrus clouds hang out, humans have increased the amount of mineral dust that arrives there through land-use changes such as deforestation and land development, Toon said. Cziczo estimates that the level of these minerals has increased by about 50 percent since the beginning of industrialization. Metallic particles are also introduced by humans through the burning of fossil fuels and other industrial activities, he said.
But how does this affect the amount or size of cirrus clouds? It's too early to say, Cziczo said, but the data from the study will help improve computer models of climate change. Toon said more mineral particles kicked up by humans could equate to more cirrus clouds, although there are many other factors that complicate the situation.
It's also unclear how cirrus clouds might affect the climate. Depending on their location in the atmosphere, they can either help cool the Earth or warm it up. Unlike liquid water clouds, which generally cool the Earth by reflecting sunlight, ice clouds can help warm it up by absorbing reflected heat, Toon said.
Cirrus clouds are unique in that they are made up of ice crystals, whereas most other clouds contain condensed droplets of liquid water. When most people think of clouds, they picture these liquid water clouds, which exist closer to the Earth's surface and are responsible for rainstorms and other weather, Cziczo said.
Like all clouds, water clouds need particles upon which to condense. Recent research has shown that these clouds can form on airborne microbes, sulfates (chemicals emitted by volcanoes and human activity) and other organic materials, Cziczo said. As this study shows, however, cirrus clouds need very specific particles upon which to nucleate and freeze.
Analyzing chemicals within high-altitude ice crystals is no easy task. To do so, Cziczo and his colleagues partnered with NASA to use two of its research airplanes. Up in the air, they used a device called a counterflow virtual impactor. This device acts like a hair dryer, Cziczo said.
"The inlet flows gas out the front of the plane. This stops the small particles we don't want to sample and only lets in the big ice crystals,” he explained. “You can imagine that if you drop a Ping-Pong ball on a hair dryer, the flow of air stops the Ping-Pong ball. But if you drop a bowling ball on the hair dryer, it has no effect. Same thing for particles versus ice crystals."
The warm air then melted the ice, and the researchers analyzed the particles using a mass spectrometer they took up in the airplane with them, Cziczo said.
More from LiveScience:
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