A dust storm (or sandstorm in some contexts) is a
meteorological phenomenon common in dry, arid and semi-arid regions. Such a
storm is usually the result of convection currents created by intense heating of
the ground. The air over the sand becomes hot, and rises. This creates
differences in air pressure and temperature, and the cooler winds begin to rush
in. The wind is strong enough to move dunes, and it often interferes with
travel, sometimes obliterating roads in flat, dry regions such as those of the
western United States. For instance, on November 29, 1991 a convective dust
storm formed over Interstate 5 in the San Joaquin Valley, California. The storm
picked up dust in a suspension with winds at speeds of over 120km/h. Visibility
was reduced to less than half a car's length, causing a pile-up accident
involving 164 cars, killing 17 and injuring 151.
The simoom or simoon (sīmūm, sīmūn) is the dust- and sand-laden desert wind
of North Africa and Arabia that contributes largely to the atmospheric dust over
Europe; evidence of the dust from simoon winds has also been found on the
seafloor at considerable distances from shore. The haboob (həbūb) is a sandstorm
prevalent in the region of Sudan around Khartoum. Sandstorms, the leading edges
of which often appear as solid walls of dust as much as 5,050 ft (1,525 m) high,
also occur, although less frequently, in the southwestern United States. One
that occurred near Tucson, Arizona on July 16, 1971 was extensively documented
by meteorologists. Similar duststorms from windborne particles are evident on
the planet Mars and are thought to be seasonal. Severe dust storms can reduce
visibility to zero, making travel impossible, and can blow away valuable
topsoil, while depositing soil in places where it may not be wanted. Drought and
wind contribute to the emergence of dust storms, as do poor farming and grazing
practices. The dust picked up in such a storm can be carried thousands of
kilometers: Sahara dust storms influence plankton growth in the western Atlantic
Ocean and, according to some scientists, are an important source of scarce
minerals for the plants of the Amazon rainforest.
Dust storms can often be observed from satellite photos, the use of which is
highly valuable in forecasting; of particular use are the NASA imaging devices
MODIS and SeaWIFS.
On other planets
Public Domain - by
NASA. |
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A massive global dust storm raging on Mars in 2001. |
Dust storms are also known to occur on a massive scale on the planet Mars.
Storms on Mars last longer, and cover larger areas, than on Earth; some of these
storms cover the entire planet and last for hundreds of days.
