A sand or dust storm is a storm or strong wind, the sand or dust carries with it. It occurs especially in deserts. A sandstorm must be distinguished from a sand pants that usually remains limited spatially close.
When one speaks in the vernacular of a sandstorm, one thinks, in most cases a dust storm.
In a sandstorm, it is a very dry and hot wind, the large amounts of sand initially stirred up high in drylands and then carries. Some storms can transport up to 100 million tons of sand, sometimes over a very long distance. The distance traveled by the sand in this case, depends on the size of the individual particles of sand. The largest particles form slow dunes sheltered from the wind. It is estimated that total by sandstorms about 2-3 billion tons of sand were moved in 2004.
Lots on the surface lying particles can be lifted into the air or along the ground are rolled (sand creep), so thus removed or eroded. This process is called deflation. If the finer particles of the size of the silt ( grain size of 0.002 mm to 0.063 mm) are lifted in dense, high clouds in the air, called the phenomenon a dust storm. This is not to be confused with a sandstorm, in which the larger sand particles (particle size 0.063 to 2 mm) are to be shipped. In this low cloud of moving sand is formed, which only a few centimeters up to max. 2 m from the ground to the height ranges.
A dust storm is approaching as dark cloud that extends from the ground up to several kilometers in height. Visibility is reduced to a few meters and fine, suffocating dust penetrates everywhere. It is estimated that one cubic meter of air can be up to 1 g of the dust.
The process in a sand storm is different. Sand is too heavy to be carried to great heights and over great distances. It is driven in a bouncing, said saltation movement over the ground.
Examples, causes, effects
Thus, for example African desert sand, which settles in the Caribbean, held responsible for the local coral death. On the other hand, Sahara sand settles out in areas of Europe that by its alkaline properties, contrary to the acid rain. In the South American rainforest, the same desert sand is used as fertilizer.
The sand from the Australian desert travels partly Brisbane. This sand contains from excretions of breeding animals in the rural steppe and desert regions bacteria Q fever. It ensures, not only for smog, but also for the increase of the disorders. Once, however, surpasses the coastlines, the consequences of the desert storm change. In the oligotrophic South Pacific, the sand is responsible for a tenfold increase in algae growth and thereby improved the livelihoods of marine mammals and fish.
Sands which are blown by the dry flats of the Aral Sea are contaminated with pesticides from the cotton-growing and provide for appropriate loads in the sedimentation areas.
An important reason for this development is the increasing use of off-road vehicles in the deserts. By SUVs thin hardened crusts are broken on the desert surface, thus destroying the erosion protection for the underlying sand. To the same effect, the introduction of cattle and sheep in the interior of Australia. The hooves destroyed the thin fouling layer.
Other reasons include the increasing desertification, deforestation and climate change.
In many areas where regular sandstorms occur, they get local names:
- Buran in the steppe and desert in Central Asia
- Chamsin or Khamsin in the Nile region and in Israel / Palestine
- Gibli or Ghibli in space Tunisia and Libya
- Haboob in the Sahara region
- Simoom in the North African- Arab
In April 2011, a sandstorm was the cause of a pileup on Highway 19 between Rostock and Güstrow.
With the establishment of the Green Wall of China is trying to curb the sandstorms that regularly afflict Beijing. Overall, the Chinese want 350,000 square kilometers of land, replant an area the size of Germany, with trees. Thus, the Green Wall is the largest reforestation project in human history.
In the synoptic one uses the following defined by the World Meteorological Organization symbols and codes for space-saving indication of a weather state with a sand or dust storm. The symbols are listed here as part of the data from a weather station in a surface weather map. The assigned number key applies to both the SYNOP and for the METAR code.
All weather symbols see: Weather map # Conditions