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A dust devil in the Mojave Desert

A dust devil in Ramadi, Iraq
Dust devil. For the indigenous American tribe see Mohave. The Mojave Desert (moʊˈhɑːvi or /məˈhɑːvi/ ( Hayikwiir Mat'aar in Mojave Ramadi ( BGN: Ar Ramādī) is a City in central Iraq, about West of Baghdad For a topic outline on this subject see List of basic Iraq topics. jpg

A dust devil at the Burning Man Festival
For other uses of this phrase, see Dust devil (disambiguation). Burning Man is an annual event held in

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). An updraft or downdraft ( air pocket) is the vertical movement of Air as a Weather related phenomenon 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. A tornado is a violent rotating column of air which is in contact with both the surface of the earth and a Cumulonimbus cloud or in rare cases the base of a Cumulus 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.

Contents

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". [1]

The Australian "willy-willy" or "whirly-whirly" is thought to derive from Yindjibarndi or a neighbouring language. For a topic outline on this subject see List of basic Australia topics. Yinjibarndi is a Pama-Nyungan language of Western Australia. Yinjibarndi is mutually intelligible with Kurrama, but the two are considered [2]

The Navajo refer to them as chiindii, ghosts or spirits of dead Navajos. The Navajo or Diné people (also spelled Navaho) of the Southwestern United States A chindi ( Navajo "ch'íįdii") is the ghost of the Navajo tribe believed to be released at dying breath 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". This article is about the country of Egypt For a topic outline on this subject see List of basic Egypt topics.

Among the Kikuyu of Kenya, the dust devil is known as ngoma cia aka, meaning "women's devil/demon". There is also a town in Kiambu district called Kikuyu, and a species of Pennisetum grass native to the Kenyan highlands named Kikuyu The Republic of Kenya is a country in East Africa. It is bordered by Ethiopia to the north Somalia to the northeast Tanzania to the south

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. In Physics, the angular momentum of a particle about an origin is a vector quantity equal to the mass of the particle multiplied by the Cross product of the position The secondary flow in the dust devil causes other hot air to speed horizontally inward to the bottom of the newly-forming vortex. In Fluid dynamics, a secondary flow is a relatively minor flow superimposed on the primary flow where the primary flow usually matches very closely the flow pattern predicted 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. [3]

The spinning effect, along with surface friction, usually will produce a forward momentum. Friction is the Force resisting the relative motion of two Surfaces in contact or a surface in contact with a fluid (e 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. [1]

Certain conditions increase the likelihood of dust devil formation.

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. [4] One such dust devil struck the Coconino County Fairgrounds in Flagstaff, Arizona on September 14, 2000. Coconino County is a County Flagstaff (Kinłání is a city located in northern Arizona, in the southwestern United States Events 81 - Domitian becomes Emperor of the Roman Empire upon the death of his brother Titus. 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. 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. The Enhanced Fujita Scale, or EF Scale, is the scale for rating the strength of Tornadoes in the United States estimated via the damage they cause [5] In 2003, a dust devil lifted the roof off a two-story building in Lebanon, Maine, causing it to collapse and kill a man inside. Lebanon is a town in York County, Maine, United States. The population was 5083 at the 2000 census [6]

Electrical activities

Dust devils, even small ones (on Earth) can produce radio noise and electrical fields greater than 10,000 volts per meter. [7] A dust devil picks up small dirt and dust particles. As the particles 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. [8]

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. [9]

Martian dust devils

A dust devil on Mars, photographed by Mars Global Surveyor. The long dark streak is formed by a moving swirling column of Martian atmosphere. The dust devil itself (the black spot) is climbing the crater wall. The streaks on the right are sand dunes on the crater floor.
A dust devil on Mars, photographed by Mars Global Surveyor. The Mars Global Surveyor ( MGS) was a US Spacecraft developed by NASA and the Jet Propulsion Laboratory and launched The long dark streak is formed by a moving swirling column of Martian atmosphere. The dust devil itself (the black spot) is climbing the crater wall. The streaks on the right are sand dunes on the crater floor.

Dust devils also occur on Mars, and were first photographed by the Viking orbiters in the 1970s. NASA 's Viking program consisted of a pair of space probes sent to Mars, Viking 1 and Viking 2. This article is about the Decade 1970-1979 For the Year 1970 see 1970. In 1997, the Mars Pathfinder lander detected a dust devil passing over it. Year 1997 ( MCMXCVII) was a Common year starting on Wednesday (link will display full 1997 Gregorian calendar The Mars Pathfinder was launched on December 4, 1996 by NASA aboard a Delta II just a month after the Mars Global Surveyor [10][11] 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. [12]

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. MER-A ( Mars Exploration Rover - A) known as Spirit, is the first of the two rovers of NASA 's Mars Exploration Rover Events 538 - Witiges, king of the Ostrogoths ends his siege of Rome and retreats to Ravenna, leaving Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Power levels dramatically increased and daily science work was anticipated to be expanded. [13] 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. MER-B ( Mars Exploration Rover - B) known as Opportunity, is the second of the two rovers of NASA 's Mars Exploration [14]

Dust devil on Mars, photographed by the Mars rover Spirit. The counter in the bottom-left corner indicates time in seconds after the 1st photo was taken in the sequence. Three other dust devils appear in the background.
Dust devil on Mars, photographed by the Mars rover Spirit. The counter in the bottom-left corner indicates time in seconds after the 1st photo was taken in the sequence. Three other dust devils appear in the background.

Related phenomena

A Fire whirl or swirl, sometimes called fire devils or fire tornadoes, can be seen during intense fires in combustible building structures or more commonly in forest or bush fires. A fire whirl, colloquially fire devil or fire tornado, is a phenomenon in which a Fire, under certain conditions (depending on air Temperature A fire whirl is a vortex-shaped formation of burning gases being released from the combustible material. The genesis of the vortex is probably similar to that of a dust devil. But, as distinct from the dust devil, it is improbable that the height reached by the fire gas vortex is greater than the visible height of the vortical flames because of turbulence in the surrounding gases which inhibit creation of a stable boundary layer between the rotating/rising gases relative to the surrounding gases. [15]

Hot cinders underneath freshly-deposited ash in recently burned areas may sometimes generate numerous dust devils. The lighter weight and the darker color of the ash may create dust devils that are visible hundreds of feet into the air.

Steam devils are phenomena often observed in the steam rising from power plants. A steam devil is the term used to describe a Rotating Updraft that involves Steam or Smoke. A power station (also referred to as generating station, power plant or powerhouse) is an industrial facility for the generation of [16]

See also

Notes

  1. ^ a b http://www.death-valley.us/article559.html
  2. ^ Dixon et al. A gustnado is a colloquial expression for a type of short-lived shallow cyclonic circulation that can form in a Severe thunderstorm. A tornado is a violent rotating column of air which is in contact with both the surface of the earth and a Cumulonimbus cloud or in rare cases the base of a Cumulus A fire whirl, colloquially fire devil or fire tornado, is a phenomenon in which a Fire, under certain conditions (depending on air Temperature A steam devil is the term used to describe a Rotating Updraft that involves Steam or Smoke. A waterspout is an intense columnar Vortex (usually appearing as a Funnel -shaped Cloud) that occurs over a Body of water and is connected to A landspout is a slang-term coined by meteorologist Howard B Bluestein in the early 1980s for a kind of Tornado not associated with the Mesocyclone of In Fluid dynamics, a secondary flow is a relatively minor flow superimposed on the primary flow where the primary flow usually matches very closely the flow pattern predicted (2006): p. 195.
  3. ^ Ludlum, David M. (1997). National Audubon Society Field Guide to North American Weather. Knopf. ISBN 0-679-40851-7.  
  4. ^ Dust Devils: Ephemeral Whirlwinds Can Stir Up Trouble. Arizona Vacation Planner (unknown). Retrieved on 2007-10-05. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 869 - The Fourth Council of Constantinople is convened to decide about what to do about Patriarch Photius of Constantinople
  5. ^ Damage From a Dust Devil at the Coconino County Fairgrounds - September 14, 2000. National Weather Service-Flagstaff, AZ (unknown). Retrieved on 2007-10-05. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 869 - The Fourth Council of Constantinople is convened to decide about what to do about Patriarch Photius of Constantinople
  6. ^ NCDC: Event Details National Climatic Data Center Accessed 2008-06-05. The United States National Climatic Data Center ( NCDC) in Asheville, North Carolina is the world's largest active Archive of 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 70 - Titus and his Roman Legions breach the middle wall of Jerusalem in the Siege of Jerusalem
  7. ^ University of California, Berkeley (29 May 2002). Events 363 - Roman Emperor Julian defeats the Sassanid army in the Battle of Ctesiphon, under the walls of the See also 2002 (disambiguation Year 2002 ( MMII) was a Common year starting on Tuesday of the Gregorian calendar. "Stalking Arizona dust devils helps scientists understand electrical, atmospheric effects of dust storms on Mars". Press release. A news release, media release, press release or press statement is a written or recorded Communication directed at members of the News Retrieved on 2006-12-01. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 800 - Charlemagne judges the accusations against Pope Leo III in the Vatican
  8. ^ Koch, J. , and N. O. Renno (Dec. 5-9, 2005). "Convective-radiative feedback mechanisms by dusty convective plumes and vortices". Fall meeting of the American Geophysical Union.  
  9. ^ Kok, J. F. ; Renno, N. O. (2006). "Enhancement of the emission of mineral dust aerosols by electric forces". Geophysical Research Letters 33 (Aug. 28): L19S10. doi:10.1029/2006GL026284. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
  10. ^ Metzger, S. M. . Dust Devil Vortices at the Ares Vallis MPF Landing Site (PDF). Mars Exploration Program. JPL. Retrieved on December 1, 2006.
  11. ^ Martian Dust Devils Caught. Climate Research USA. Ruhr-Universität Bochum (March 21, 2000). Events 630 - Byzantine emperor Heraclius restores the True Cross to Jerusalem. 2000 ( MM) was a Leap year that started on Saturday of the Common Era, in accordance with the Gregorian calendar. Retrieved on December 1, 2006.
  12. ^ Smith, Peter; Renno, Nilton (6 June 2001). Events 1508 - Maximilian I Holy Roman Emperor, is defeated in Friulia by Venetian forces; he is forced to sign a three-year Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. Studying Earth Dust Devils For Possible Mars Mission. UniSci News. Retrieved on December 1, 2006.
  13. ^ David, Leonard (12 March 2005). Events 538 - Witiges, king of the Ostrogoths ends his siege of Rome and retreats to Ravenna, leaving Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. Spirit Gets A Dust Devil Once-Over. Space. com. Retrieved on December 1, 2006.
  14. ^ Did You Know?. Mars Exploration Rovers. Cornell University. Retrieved on December 1, 2006.
  15. ^ WILDFIRE MODELING, IR OBSERVATIONS AND ANALYSIS
  16. ^ Lyons, Walter A. The Handy Weather Answer Book. Detroit, MI: Visible Ink Press, 1997.

References

External links

Dictionary

dust devil

-noun

  1. A small atmospheric vortex appearing in clear, dry conditions, made visible by swirling dust picked up from the ground.
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