Thunderstorm, Florida Photograph by Michael Roberts,Your ShotIt rains almost every afternoon in the sunshine state. I work in a strip mall and left work to threatening, but beautiful, skies. I put on a long lens, intending to shoot only these treetops and sky. It immediately poured rain, forcing me into the car. What a blessing. I used the long lens and focused on the rain-covered windshield. It lessened the depth of field, adding to image distortion, eliminating strip mall clutter, and creating an image with the feel of a Florida afternoon thunderstorm. Download Wallpaper (1600 x 1200 pixels)
Sailboat at Sea, Germany Photograph by Patrick LieninWhile hiking at Jasmund National Park in northwest Germany, a rainstorm passed by and created a stunning scene! The sea was completely flat and the only thing out there was the tiny sailing boat. Download Wallpaper (1600 x 1200 pixels)
Ginza, Tokyo Photograph by Navid BaratyA rainy business day during the lunch hour in Ginza, Tokyo
Planes Create Weird Clouds—And Snow, Rain Fall Out

A hole-punch cloud over Mobile, Alabama, in 2003. ;Weatherthings

Brian Handwerk
for National Geographic News
Published June 16, 2010

A few years ago scientists were surprised by the sight of two planes carving a hole through a cloud—which then began spewing snow.

A new study spawned by the accidental discovery solves the mystery behind so-called hole-punch clouds and explains how airplanes can change the weather, at least on an extremely local level.

Scientists have studied hole-punch clouds since the 1940s and have long suspected that planes play a role in their formation. (See pictures of a potentially new type of cloud.)

Now, ice microphysicist Andrew Heymsfield and colleagues have found that aircraft really can create the odd clouds. Their research also uncovered something totally new: that aircraft can unleash precipitation by carving the cloud tunnels, which had never before been observed.

(Pictures: “Night Shining Clouds Getting Brighter.”)

How Planes Can Make It Rain

Clouds at a certain the right altitude and temperature—relatively common over western Europe and the U.S. Pacific Northwest, for example—are saturated with water droplets cooled to about 5 degrees Fahrenheit (minus 15 degrees Celsius).

Because the water in these clouds is so pure—with no particles around which vapor can condense and freeze—the droplets remain liquid down to minus 35 degrees Fahrenheit (minus 34 degrees C). If the cloud gets much colder, though, they freeze into ice particles that can produce rain or snow.

When a plane’s propeller, for example, spins through a cloud, the propeller exerts a rearward force. The force expands air, cooling by as much as 54 degrees Fahrenheit (30 degrees Celsius), said Heymsfield, of the National Center for Atmospheric Research (NCAR) in Boulder, Colorado.

Jets do the same thing when air is forced over their wings, though jets cool air by only about 36 degrees Fahrenheit (20 degrees Celsius).

As planes push cloud temperatures past the tipping point at which supercooled water freezes, the aircraft “seed” the clouds with ice particles, the study says.

“If you introduce ice particles, water vapor will condense on them—like it does on a bathroom mirror that’s just a bit cooler than the room—and then snow out” or rain out, Heymsfield explained.

(Download our weather pictures.)

Hole-Punch Cloud Discovery a Surprise

Heymsfield and colleagues flew smack-dab into the hole-punch discovery after having conducting a cloud study from a heavily instrumented turboprop plane near Denver International Airport in 2007.

A later look at ground-based radar showed an unexplained band of snowfall in the area.

“When we went back to our forward- and downward-looking video camera data, we could see a canal-like hole” in block of clouds, he said.

“And we could look down and see a snow shaft falling out of the hole to the ground.”

U.S. Federal Aviation Administration records show that another turboprop followed the same path in short order. The snow squall began five minutes after the second plane had passed. Snow fell for 45 minutes along a band 20 miles (32 kilometers) long and 2.5 miles (4 kilometers) wide, dropping some two inches (five centimeters) on the ground under the band.

Because hole punching triggers dynamic events within the clouds, he added, the new research, published this month in the Bulletin of the American Meteorological Society, could improve our understanding of cloud circulation.

And the discovery could someday lead to better efforts at producing rainfall by cloud seeding (pictures of seven emergency climate fixes), he added—meaning that, for a change, the weather could be at the mercy of planes, rather than the other way around.

(Source)

Photo and caption by Eleanne GreyWhen I took this shot, the weather was at the same time gray and very bright in several places. Mostly the sun rays lay on the raindrops and were just a bit reflected on grass—quite a weird natural happening. I’ve remembered this scene like I interpreted it here, a magical still moment, drawn by the nature, drawn by the rain and sunlight. It looked like a painting. Download Wallpaper (1600 x 1200 pixels)
Chimp Call Photograph by Ian Nichols This Month in Photo of the Day: National Geographic Magazine FeaturesAs rain falls in Congo’s NouabaléNdoki National Park, a chimp adds to the chorus of excited calls ringing through the forest. Download Wallpaper (1600 x 1200 pixels)
Children Playing in Rain, Bangladesh Photograph by Jashim Salam, Your Shot This Month in Photo of the Day: Nature and EnvironmentChildren playing in seasonal rains are a great sight of monsoon and six seasons here in Bangladesh. The effect of climate change is making this rare as less or more rain is causing great disturbances around the country. Heavy rain causes floods and landslides, and makes millions homeless and takes the lives of many others. The climate should behave like normal for our future children to play like this in monsoon rains, and people must take responsibility to reduce pollution and save our world.