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Dust devil
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| [Note Guidelines] Photographer's Note |
Dust devil
A dust devil is a rotating updraft, ranging from small (half a meter wide and a few meters tall) to large (over 10 meters wide and over 1000 meters tall). Dust devils are usually harmless, but rare ones can grow large enough to threaten both people and property. They are comparable to tornadoes in that both are an unusual weather phenomenon of swirling air vortices. Tornadoes form as an updraft attached to a wall cloud at the back of a thunderstorm. Dust devils form as an updraft under sunny conditions during fair weather, rarely coming close to the intensity of a tornado.
Names
In the southwestern United States, a dust devil is sometimes called a "dancing devil". In Death Valley, California, it may be called a "sand auger" or "dust whirl".
The Australian "willy-willy" or "whirly-whirly" is thought to derive from Yindjibarndi or a neighbouring language.
The Navajo refer to them as chiindii, ghosts or spirits of dead Navajos. If a chindi spins clockwise it is said to be a good spirit; if it spins counterclockwise it is said to be a bad spirit.
Egypt has its fasset el 'afreet or "ghost's wind".
Among the Kikuyu of Kenya, the dust devil is known as ngoma cia aka, meaning "women's devil/demon".
We sometimes here in India experience this thing on dried river beds and large fields. We call it in our language i.e. Oriya "Khandia Bhoota" Khandia=Injury Bhoota=Ghost or Injured Ghost.
Formation
Dust devils form when hot air near the surface rises quickly through a small pocket of cooler low pressure air above it. If conditions are just right, the air may begin to rotate. As the air rises suddenly, the column of hot air is stretched vertically causing intensification of the spinning effect by the scientific principle conservation of angular momentum. The secondary flow in the dust devil causes other hot air to speed horizontally inward to the bottom of the newly-forming vortex. As more hot air rushes in toward the developing vortex to replace the air that is rising, the spinning effect becomes further intensified and self-sustaining. A dust devil, fully formed, is a funnel-like chimney through which hot air moves, both upwards and in a circle. As the hot air rises it cools, loses its buoyancy and eventually ceases to rise. As it rises it displaces air which descends outside the core of the vortex. This cool air returning acts as a balance against the spinning hot air outer wall and keeps the system stable.
The spinning effect, along with surface friction, usually will produce a forward momentum. The dust devil is able to sustain itself longer by moving over nearby sources of hot surface air.
As available extreme hot air near the surface is channeled up the dust devil, eventually surrounding cooler air will be sucked in. Once this occurs, the effect is dramatic and the dust devil dissipates in seconds. Usually this occurs when a dust devil isn't moving fast enough (depletion) or begins to enter a terrain where the surface temperatures are cooler, causing unbalance.
Certain conditions increase the likelihood of dust devil formation.
* Flat barren terrain, desert or asphalt: Flat conditions increase the likelihood of the hot air "fuel" to be a near constant. Dusty or sandy conditions will cause particles to become caught up into the vortex, making the dust devil easily visible.
* Clear skies or lightly cloudy conditions. The surface needs to absorb significant amounts of solar energy from the Sun to heat the air near the surface and create ideal dust devil conditions.
* Light or no wind and cool atmospheric temperature. The underlying factor and sustainability of a dust devil is the extreme difference in temperature between the near surface air and atmosphere. Wind conditions will destabilize the spinning effect of a dust devil.
Intensity and duration
On Earth, most dust devils are very small and weak, often less than 3 feet (0.9 meters) in diameter with maximum winds averaging about 45 miles per hour (70 km/h), and they often dissipate less than a minute after forming. On rare occasions, a dust devil can grow very large and intense, sometimes reaching a diameter of up to 300 feet (90 meters) with winds in excess of 60 mph (100 km/h), and can last for upwards of 20 minutes before dissipating. One such dust devil struck the Coconino County Fairgrounds in Flagstaff, Arizona on September 14, 2000. Extensive damage occurred to several temporary tents, stands and booths, as well as some permanent fairgrounds structures. In addition, several injuries were reported, but there were no fatalities. Based on the degree of damage left behind, it is estimated that the dust devil produced winds as high as 75 mph (120 km/h), which is equivalent to a moderate-strength EF0 tornado.
Electrical activities
Dust devils, even small ones (on Earth) can produce radio noise and electrical fields greater than 10,000 volts per meter. A dust devil picks up small dirt and dust particles. As the particle whirl around they bump and scrape into each other and become electrically charged. The whirling charged particles also create a magnetic field that fluctuates between 3 and 30 times each second.
These electrical fields assist the vortices in lifting materials off the ground and into the atmosphere. Field experiments indicate that a dust devil can lift 1 gram of dust per second from each square meter (10 lb/s from each acre) of ground it passes over. A large dust devil measuring about 100 meters (330 ft) across at its base can lift about 15 metric tons (17 short tons) of dust into the air in 30 minutes. Giant dust storms that sweep across the world's deserts contribute eight percent of the mineral dust in the atmosphere each year during the handful of storms that occur. In comparison, the significantly smaller dust devils that twist across the deserts during the summer lift about three times as much dust, thus having a greater combined impact on the dust content of the atmosphere. When this occurs, they are often called sand pillars.
Martian dust devils
Dust devils also occur on Mars, and were first photographed by the Viking orbiters in the 1970s. In 1997, the Mars Pathfinder lander detected a dust devil passing over it. Martian dust devils can be up to fifty times as wide and ten times as high as terrestrial dust devils, and large ones may pose a threat to terrestrial technology sent to Mars.
Mission members monitoring the Spirit rover on Mars reported March 12, 2005 that a lucky encounter with a dust devil has cleaned the solar panels of that robot. Power levels dramatically increased and daily science work was anticipated to be expanded. A similar phenomenon (solar panels mysteriously cleaned of accumulated dust) had previously been observed with the Opportunity rover, and dust devils had also been suspected as the cause.
A large-scale cyclone has also been observed on Mars. |
goldyrs, boreocypriensis, jcoowanitwong, JoseMiguel, ramthakur, Argus, jaycee, matatur, mariki, cataclysta, cicindela, eqshannon, uleko, Silvio2006 has marked this note useful
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Haraprasan,
How beautifully captured!!nice pov/dof!!
Great job and very useful note!!
Thanks!
Regards,\Goldy
Hi friend Haraprasan,
An excellent capture of this dust devil rotating updraft with excelent details,Sharpnes, lighting and even clarity friend. Great!
TFS and Regards,
Bayram
HI Haraprasan,
Great to witness and able to take a photo of this natural phenomenon. Sharp and well seen image. Very nice pov and composition. TFS this fine image.
JC
Hi Haraprasan,
Very interesting presentation!
A great timing to catch this phenomenon at full action.
So good to have this nature event "materialized" thanks to the dust that it carries.
Very well done and thanks for share.
My best regards,
JM
An unusual subject in the form of this dust devil, HP.It is quite conspicous in your picture and looks like a little tornado.
Thanks for showing this well captured natural phenomenon.
Ram
- Argus
![Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 2707 W: 139 N: 7809]](http://i1.treknature.com/misc/g-g-g.gif)
(24333) - [2008-02-25 6:20]
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Hello Haraprasan,
Excellent capture of swirling dust in a whirlwind. I hope the dust didn't get into your equipment! Even though the 400D has a sensor cleaning system.
Very resourceful of you to take a shot of this.
Thanks for sharing this well composed image of one of the forces of Nature.
Ivan
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- joey
(21398)
- [2008-02-25 8:08]
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Something very different today!
What a great atmospheric shot of this Dust Devil!
I remember seeing a very mini one way back while I was at my primary school.
I like the slight blur which gives a sense of movement.
Nice lighting and colours.
Very well done Haraprasan,
Joe
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- jaycee
![Gold Star Critiquer/Gold Note Writer [C: 1865 W: 8 N: 4848]](http://i1.treknature.com/misc/g-n-g.gif)
(15703) - [2008-02-25 9:21]
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Hi Haraprasan,
A superb shot of this dust devil and very informative notes. I don't think I have seen anything like this before - just dust storms in Phoenix. You captured it perfectly.
Jane
Interesting capture of a natural phenomenon Haraprasan, thank you for the detailed information and terminology my friend, in Turkish we shortly call this phenomenon a "hortum", which is a kind of proboscis!
Yours,
Mehmet
HI Haraprasan
Very good photo and informative note Great educational presentation
TFS
Krzysztof
Hello Haraprasan, very impressive shot realy well captured with good details and splendid colours, fine composition,
cheer,
friendly,
Pat
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- lousat
(11160)
- [2008-02-25 15:21]
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Hi Hara,this is very very interesting and the pic is wonderfull,great work,thanks for share,Luciano
I have seen these and I was in a couple of them...In a strange qay they are sort of fun to be in as long as you keep your eyes shut. Mine were it the Sacramento Valley of California nearby where I had bought a home and there was a large plot of empty dusty farmland behind...
Bob
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- mariki
(8981)
- [2008-02-26 0:31]
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Hello Haraprasan,
Very nice picture of this "mini-tornado". Good composition and sharpness. Good natural colours.
Cheers,
Mariki
Hello Haraprasan!
This is really strange presentation. And thanks to it very original too. I do not remember any picture on TN presenting... wind! So bravo for showing us something really very non-commercial picture!
According to the note this time I found more than "a lot" of details which were not known for me :)
All the best my Friend!
Friendly yours,
Radomir
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- gannu
(11717)
- [2008-02-26 1:31]
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WoW beautiful captured subject. I just dont know you were waiting for such thing to happen. Lovely shot. Ganesh
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- uleko
(24475)
- [2008-02-26 3:32]
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Hello Haraprasan,
I've never heard of Dust Devils before!! But your image and notes have explained them very well indeed! I expect they're what we call whirlwinds that we don't see too much of here.
This is very skilfully captured at the right moment and I like your composition!
Many thanks and regards, Ulla
Hi Haraprasan,
Nice one. You could have tried a slower shutter speed to give it an impression of motion.
Regards,
- Nirmal
Hi Haraprasan, interesting view of smoking earth, beautiful colors, great loooong note:), very well done, ciao Silvio
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- arfer
![Gold Star Critiquer [C: 2731 W: 0 N: 0]](http://i1.treknature.com/misc/g-n-n.gif)
(0) - [2008-03-01 18:16]
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Hello Haraprasan
Great timing to capture this moment.
You have excellent detail and motion captured here.
The lighting is very good.
Excellent POV.
TFS
Rob
![Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 594 W: 14 N: 1102]](http://i1.treknature.com/misc/g-s-g.gif)
(5904)