موضوع انجليزي
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موضوع انجليزي عن dust storm للصف
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تقرير عن العواصف الرملية
جمل عن dust storm
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معنى كلمة عاصف بالانجليزي
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موضوع انجليزي عن dust storm للصف
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تعبير عن dust storm
A sandstorm is a meteorological phenomenon that is manifested by
strong winds causing deflation and the transport of sand particles into the
atmosphere, by the saltation process, or even by suspension for fine sand. The
dust storms are similar but the raised substrate is the dried soil.
These phenomena are common in the Great Plains of North America, in
the Arabian Peninsula, in the Gobi Desert in Mongolia, in the Taklamakan Desert
in western China, in the Sahara Desert in Africa, in the Thar Desert in India,
as well as in other arid and semi-desert regions.
Weather causes
There are several phenomena that can lift sand or dust to give such
storms. They can be classified into two categories:
• intense meteorological depressions and fronts that generate
strong to violent winds over a diameter of several hundred kilometers;
• Mesoscale effects, such as thunderstorms, where the winds of the
middle levels of the atmosphere are bent to the ground forming a more limited
gust front that can sweep over a region.
Synoptic storms
In the first case, the action of the winds is exercised over vast
territories and lasts up to a few days. They will lift the thin surface layer
in a desert region and give visibility from reduced to zero depending on the
variations of their speed. This is an effect similar to blowing snow, or high
snow plow, in a snowstorm.
It is often a strong zone of winds when approaching a cold or
near-stationary front during the summer period in the intertropical convergence
zone. There is usually a strong wind parallel to the front in this situation
which raises sand or dust. On the other hand, in winter, it is generally the
winds behind and perpendicular to the front which are very strong because of
the intrusion of cold air of the front which makes the air unstable.
One of the synoptic scale sandstorms occurs when a north wind,
called "Shamal" or "Chammal", blows over the Arabian
Peninsula. This situation occurs in summer behind a cold front; and in winter
when there is heavy traffic between an anticyclone on the peninsula and a
depression east of the Persian Gulf1. Other known winds from desert areas give
sandstorms on the same scale as Harmattan, Simoun, Sirocco, etc.
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