Dust storm 60605 225337812 2008-07-13T04:23:36Z Mboverload 49010 Reverted edits by [[Special:Contributions/69.86.96.168|69.86.96.168]] ([[User talk:69.86.96.168|talk]]) to last revision (224704048) by using [[WP:VPRF|VP]] {{Redirect|Sandstorm}} [[Image:Sandstorm.jpg|thumb|300px|A [[sandstorm]] approaching [[Al Asad]], [[Iraq]], just before nightfall on [[April 27]] 2005.]] A '''dust storm''' or '''sandstorm''' is a [[meteorological phenomenon]] common in [[arid]] and [[semi-arid]] regions and arises when a gust front passes or when the wind force exceeds the threshold value where loose sand and dust are removed from the dry surface. Particles are transported by [[Saltation (geology)|saltation]] and suspension, causing [[soil erosion]] from one place and [[deposition]] in another. The [[Sahara]] and [[dryland]]s around the [[Arabian peninsula]] are the main source of airborne dust, with some contributions from [[Iran]], [[Pakistan]] and [[India]] into the [[Arabian Sea]], and [[China|China's]] storms deposit dust in the [[Pacific]]. It has been argued that recently, poor management of the Earth's drylands, such as neglecting the [[fallow]] system, are increasing dust storms from desert margins and changing both the local and global climate, and also impacting local economies.<ref name="vrs">{{ci te web |url=http://www.unccd.int/publicinfo/duststorms/part1-eng.pdf |title=Physics, Mechanics and Processes of Dust and Sandstorms |author=Victor R. Squires |publisher=Adelaide University, Australia |accessdate=2007-07-29}} 'Dust storms are a symptom of poor land management' ... 'True deserts are rarely the source of dust storms' ... 'desert margins are more often the principal source of damaging dust storms' ... 'Sahara region is the main source of aeolian dust' </ref> The term ''sandstorm'' is used most often in the context of [[desert]] sandstorms, especially in the Sahara, when, in addition to fine particles obscuring visibility, a considerable amount of larger sand particles are blown closer to the surface. The term ''dust storm'' is more likely to be used when finer particles are blown long distances, especially when the dust storm affects [[urban area]]s. ==Causes== [[Image:Dust-storm-Texas-1935.png|thumb|right|United States [[Dust Bowl]], from [[1935]]]] As the force of wind passing over loosely held particles increases, particles of sand first start to vibrate, then to saltate ("leap"). As they repeatedly strike the ground, they loosen smaller particles of dust which then begin to travel in suspension. At wind speeds above that which causes the smallest to suspend, there will be a population of dust grains moving by a range of mechanisms: suspension, saltation and creep.<ref name="vrs">{{cite web |url=http://www.unccd.int/publicinfo/duststorms/part1-eng.pdf |title=PHYSICS, MECHANICS AND PROCESSES OF DUST AND SANDSTORMS |author=Victor R. Squires |publisher=Adelaide University, Australia |accessdate=2007-07-29}} 'Once ejected, these particles move in one of three modes of transport depending on particle size, shape and density ... designated suspension, saltation and creep' </ref> A recent study finds that the initial saltation of sand particles induces a static electric field by friction. Saltating sand acquires a negative charge relative to the ground which in turn loosens more sand particles which then begin saltating. This process has been found to double the number of particles predicted by previous theory. <ref> [http://www.eurekalert.org/pub_releases/2008-01/uom-esf010708.php Electric Sand Findings, University of Michigan Jan. 6, 2008] </ref> Particles become loosely held mainly due to drought or arid conditions, and wind has varied causes. Gust fronts may be produced by the outflow of rain-cooled air from an intense thunderstorm, or they may represent a dry [[cold front]], that is, a cold front that is moving into a dry air mass and is producing no [[Precipitation (meteorology)|precipitation]]. This is the type of dust storm which was common during the [[Dustbowl]] years in the U.S. Following the passage of a dry cold front, [[convection|convective]] instability resulting from cooler air riding over heated ground can maintain the dust storm initiated at the front. In desert areas, dust and sand storms are most commonly caused by either thunderstorm outflows, or by strong pressure gradients which cause an increase in wind velocity over a wide area. The vertical extent of the dust or sand that is raised is largely determined by the stability of the atmosphere above the ground as well as by the weight of the particulates. In some cases, dust and sand may be confined to a relatively shallow layer by a low-lying [[temperature inversion]]. In other instances, dust (but not sand) may be lifted as high as 20,000&nbsp;feet (6,100&nbsp;m) high. [[Drought]] and [[wind]] contribute to the emergence of dust storms, as do poor [[farming]] and grazing practices by exposing the dust and sand to the wind.<!-- this needs expansion as poor practices are becoming the major cause of increased dust storms and so erosion, see ref name="vrs" --> ==Physical and environmental impacts== A sandstorm can move whole sand dunes. Dust storms can carry large amounts of dust, so much so that the leading edge of one can appear as a solid wall of dust as much as 1.6&nbsp;km (1&nbsp;mile) high. Dust and sand storms which come off the [[Sahara Desert]] are locally known as a [[simoom]] or simoon (sîmūm, sîmūn). The ''[[haboob]]'' (həbūb) is a sandstorm prevalent in the region of [[Sudan]] around [[Khartoum]]. The [[Sahara]] desert is a key source of dust storms, particularly the [[Bodélé Depression]]<ref>[http://www.iop.org/EJ/abstract/1748-9326/1/1/014005 The Bodélé depression: a single spot in the Sahara that provides most of the mineral dust to the Amazon forest.] Ilan Koren et al 2006 Environ. Res. Lett. 1 014005 (5pp) doi:10.1088/1748-9326/1/1/014005 'about half of the annual dust supply to the Amazon basin is emitted from a single source: the Bodélé depression'</ref> and an area covering the confluence of [[Mauritania]], [[Mali]], and [[Algeria]].<ref>[http://links.jstor.org/sici?sici=0020-2754%282001%292%3A26%3A2%3C165%3ASDSAT%3E2.0.CO%3B2-F&size=LARGE&origin=JSTOR-enlargePage Saharan Dust: Sources and Trajectories] N. J. Middleton, A. S. Goudie Transactions of the Institute of British Geographers, New Series, Vol. 26, No. 2 (2001), pp. 165-181</ref> Saharan dust storms have increased approximately 10-fold during the half-century since the 1950s, causing topsoil loss in [[Niger]], [[Chad]], northern [[Nigeria]], and [[Burkino Faso]]. In Mauritania there were just two dust storms a year in the early 1960s, but there are about 80 a year today, according to Andrew Goudie, a professor of geography at Oxford University.<ref>[http://www.ipsnews.net/news.asp?idnews=38343 ENVIRONMENT: Around the Globe, Farmers Losing Ground] Analysis by Lester R. Brown (Jun 27, 2007)</ref><ref>http://www.earth-policy.org/Books/Seg/PB2ch05_ss3.htm LOSING SOIL Lester R. Brown</ref> Levels of Saharan dust coming off the east coast of Africa in June (2007) were five times those observed in June 2006, and were the highest observed since at least 1999, which may cool Atlantic waters enough to slightly reduce hurricane activity in late 2007.<ref>http://www.sciam.com/article.cfm?alias=scientists-examine-africa&chanId=sa003&modsrc=reuters Scientists examine African dust link to hurricanes ScientificAmerican.com August 10, 2007 "These last couple months have been the dustiest summer since 1999, about five times as dusty as last year. Right now ocean temperatures are cooler than average," said Amato Evan, a climate researcher at the University of Wisconsin. "There's a big difference compared to the last two years." </ref><ref>[http://www.theadvertiser.com/apps/pbcs.dll/article?AID=/20070705/NEWS01/707050313/1002/NEWS01 Storm Report: Dry air inhibits storms] Saharan winds limit formation in warm Gulf Jim Bradshaw, 2007 July 5. Jeff Masters:"Levels of Saharan dust coming off the east coast of Africa in June were five times those observed in June 2006, and were the highest observed since at least 1999"</ref><!-- not in cite: The hurricane center tracks dust storms to assess their impact on tropical storm development. --> ==Economic impact== Dust storms cause soil loss from the dry lands, and worse, they preferentially remove organic matter and the nutrient-rich lightest particles, thereby reducing agricultural productivity. Also the abrasive effect of the storm damages young crop plants. Other effects that may impact the economy are: reduced visibility affecting aircraft and road transportation; reduced sunlight reaching the surface; increased cloud formation increasing the heat blanket effect; high level dust sometimes obscures the sun over Florida; effects on human health of breathing dust. Dust can also have beneficial effects where it deposits: Central and South American rain forests get most of their mineral nutrients from the Sahara; iron-poor oceans regions get iron; and dust in Hawaii increases [[plantain]] growth. In northern China as well as the mid-western U.S., ancient dust storm deposits known as [[loess]] are highly fertile soils, but they are also a significant source of contemporary dust storms when soil-securing vegetation is disturbed. ==Extraterrestrial dust storms== See [[Climate of Mars#Effect of dust storms]]. ==Notable dust storms== * A series of dust storms displaced hundreds of thousands of agricultural workers in the central [[United States]] and [[Canada]] during the [[Dust Bowl]]. * A dust storm that occurred near Tucson, Arizona, USA on [[July 16]], [[1971]] was extensively documented by meteorologists. * On the afternoon of [[February 8]], [[1983]], a huge dust storm originating in the [[The Mallee|Mallee]] region of [[Victoria (Australia)|Victoria]], [[Australia]] covered the city of [[Melbourne]]. * On Saturday afternoon of [[February 24]], [[2007]], a large dust storm originating in the West [[Texas]] area of [[Amarillo]] covered much of the [[North Texas]] area. Strong winds caused extensive [[property damage]] to fences, roof shingles, and some buildings. The [[DFW Airport]] was severely affected, causing extensive flight delays into and out of the DFW area. Area residents suffered [[respiratory]] problems and [[allergic reactions]], causing many people to visit hospitals. This event was also marked by relative humidities down to 1 per cent, in one case the juxtaposition of a c. 70°F air temp and dew point of -20°F, in and around of the area affected. * The multi-year droughts in portions of North America of 1954-56, 1976-78, and 1987-91 were noted for dust storms of the intensity seen in the middle 1930s over some fraction of their coverage and timespan, and more sporadically during the times between. The three multi-year droughts were similar to the 1930s in storms being raised by synoptic scale weather events such as cyclones and cold fronts; otherwise the most common trigger is the outflow from convective activity, known as a [[haboob]]. Significant events of the latter variety occurred in Colorado and Kansas in May 2004 with winds to 100 mph, Minnesota and Wisconsin in June 2004 causing significant damage, and the upper Middle West in May 1988, notable for strong electrification and lightning activity and by one estimate reaching 30 000 ft or more. The first and third of this list reached black blizzard intensity, causing total blackout for some period ranging from 90 sec to 10 or more minutes, over some fraction of the ground covered. The 1987-91 drought was especially notable as in the 1930s for the large number of rain of mud events, often generated by dust in suspension and/or carried on upper-level winds. * Just one of many notable storms in the 1930s, the storm of 9.-11. May 1934 began in the far north-western Great Plains and proceeded east over the nothern tier of states and parts of Canada and was notable for removing the vast majority of the soil deposited since the last Ice Age over some parts of its path. * In June 2007, a large dust storm struck Karachi Pakistan and areas of the Sindh and lower Balochistan, followed by a series of heavy rainfalls which resulted in a death toll of nearly 200. ==Gallery== <gallery> Image:Sahara dust plume Nov 1998.jpg|Dust plume off the Sahara desert over the northeast Atlantic Ocean. Image:Zandstorm.jpg|Dust storm in [[Burkina Faso]] Image:Mars duststorm.jpg|Martian dust storm Image:Mars dust opacities MER-B Sol 1205 to 1235.jpg|Time-lapse composite of the Martian horizon during Sols 1205 (0.94), 1220 (2.9), 1225 (4.1), 1233 (3.8), 1235 (4.7) shows how much sunlight the July 2007 dust storms blocked; Tau of 4.7 indicates 99% blocked. credit:NASA/JPL-Caltech/Cornell </gallery> ==See also== *[[Asian Dust]] *[[Dust Bowl]] *[[Fog]] *[[Haboob]] *[[Sirocco]] *[[Saharan Air Layer]] *[[Saharan dust]] *[[Shamal (wind)]] ==References== {{reflist|1}} 9. Saharan Dust Has Chilling Effect on North Atlantic http://www.nasa.gov/topics/earth/features/cooling_dust.html ==External links== {{Commons|Dust storm}} *[http://lubbockonline.com/gallery/dirtygallery/index.htm Slide Show of a Dust Storm] in [[Lubbock, Texas]] on [[December 15]], [[2003]] *[http://www.islandnet.com/~see/weather/almanac/arc2002/alm02jun.htm ''Dust in the Wind''] *[http://video.google.com/videoplay?docid=1120793438507203379 Video of a dust storm in Al Asad Iraq, April 27, 2005] *[http://www.maniacworld.com/Sahara-Sandstorm.html Video of a Sahara Sandstorm] *[http://texashistory.unt.edu/browse/subject/Texas_Landscape_and_Nature/Natural_disasters/Dust_storms/ Photos of dust storms] hosted by the [http://texashistory.unt.edu/ Portal to Texas History]. *[http://www.lbk.ars.usda.gov/wewc/biblio/bar.htm The Bibliography of Aeolian Research] *[http://www.dallasnews.com/sharedcontent/dws/news/texassouthwest/stories/022507dntswdustblast.9733cf.html ''Storms tear through Texas, neighbor states; Property damage, fires, injuries reported; Arkansas hit hardest ''] *[http://cbs2chicago.com/national/topstories_story_056164157.html ''Dallas dust storm causes LAX delays, cancellations''] [http://www.atmo.arizona.edu/research/dust/dust.html ''University of Arizona Dust Model Page''] [[Category:Storms]] [[Category:Weather hazards|Dust storm]] [[af:Sandstorm]] [[ar:عاصفة رملية]] [[bg:Пясъчна буря]] [[ca:Tempesta de pols]] [[cs:Písečná bouře]] [[da:Sandstorm]] [[de:Sandsturm]] [[es:Tormenta de polvo]] [[fr:Tempête de sable]] [[id:Badai pasir]] [[he:סופת חול]] [[lt:Smėlio audra]] [[nl:Zandstorm]] [[ja:砂嵐]] [[no:Sandstorm]] [[nn:Sandstorm]] [[pl:Burza piaskowa]] [[pt:Tempestade de areia]] [[fi:Hiekkamyrsky]] [[uk:Пилова буря]] [[zh:沙尘暴]]