Dust storm

Dust storm/Sand storm
Sandstorm in Al Asad, Iraq.jpg
A sandstorm approaching Al Asad, Iraq, just before nightfall on April 27, 2005.
Sign Dust rising in the air.
Type Mild
Effect May cause coughing and spread dust.

A dust storm is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Fine particles are transported by saltation and suspension, a process that moves soil from one place and deposits it in another.

Drylands around North Africa and the Arabian peninsula are the main terrestrial sources of airborne dust. Also with some contributions from Iran, Pakistan and India into the Arabian Sea, and China's significant storms deposit dust in the Pacific.[ clarification needed] It has been argued that recently[ clarification needed], poor management of the Earth's drylands, such as neglecting the fallow system, are increasing dust storms size and frequency from desert margins and changing both the local and global climate, and also impacting local economies. [1]

The term sandstorm is used most often in the context of desert sandstorms, especially in the Sahara Desert, or places where sand is a more prevalent soil type than dirt or rock, 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 areas.

Causes

As the force of wind passing over loosely held particles increases, particles of sand first start to vibrate, then to saltate ("leaps"). As they repeatedly strike the ground, they loosen and break off 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. [1]

Animation showing the global movement of dust from an Asian dust storm.

A study from 2008 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 theories. [2]

Particles become loosely held mainly due to drought or arid conditions, and varied wind causes. Gust fronts may be produced by the outflow of rain-cooled air from an intense thunderstorm. Or, the wind gusts may be produced by a dry cold front, that is, a cold front that is moving into a dry air mass and is producing no precipitation—the type of dust storm which was common during the Dust Bowl years in the U.S. Following the passage of a dry cold front, 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 feet (6,100 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.

One poor farming practice which contributes to dust storms is dryland farming. Particularly poor dryland farming techniques are intensive tillage or not having established crops or cover crops when storms strike at particularly vulnerable times prior to revegetation. [3] In a semi-arid climate, these practices increase susceptibility to dust storms. However, soil conservation practices may be implemented to control wind erosion.

Other Languages
Afrikaans: Sandstorm
العربية: عاصفة رملية
azərbaycanca: Qum fırtınası
български: Пясъчна буря
dansk: Sandstorm
Deutsch: Sandsturm
Ελληνικά: Αμμοθύελλα
Esperanto: Sabloŝtormo
euskara: Hauts ekaitz
فارسی: طوفان شن
한국어: 모래폭풍
Bahasa Indonesia: Badai pasir
עברית: סופת חול
қазақша: Шаңды дауыл
lietuvių: Smėlio audra
Bahasa Melayu: Ribut pasir
မြန်မာဘာသာ: သဲမုန်တိုင်း
Nederlands: Zandstorm
日本語: 砂嵐
norsk: Sandstorm
norsk nynorsk: Sandstorm
русский: Пыльная буря
Simple English: Dust storm
slovenčina: Prachová búrka
srpskohrvatski / српскохрватски: Pješčana oluja
svenska: Sandstorm
українська: Пилова буря
Tiếng Việt: Bão cát
中文: 沙尘暴