The Sahara (Arabic: al-As-Sahara Kobra, الصحراء الكبرى, the Grand Desert and steppe ) is a large ecoregion desert located in the northern part of the African continent . It stretches over 5000 kilometers of the Atlantic to the Red Sea and covers nearly 8 million square kilometers , an area the size of Australia. It extends beyond the Red Sea and geographers speak of a large Saharan-Arabian desert. The Sahara is the western part of a broad dry diagonal stretching from the outskirts of the Senegal River until Mongolia . Considered the largest hot desert in the world, it divides the continent from north to south. It covers vast expanses of territory and extends the territory of ten States : the Algeria , the Tunisian , the Morocco , the Libya , the Egypt , the Sudan , the Chad , the Niger , the Mali , the Mauritanian and the disputed territory of Western Sahara . Contrary to popular belief, the sandy desert covers only 20% of the area of ​​the Sahara. Most travelers know the images of sandy deserts ( Grand Erg Oriental and the Grand Erg Occidental ) but neglect those mountains ( Hoggar , Tassili , Tibesti ) of hamadas , the regs (Tanezrouft) and huge regions covered webs sand like Majabat al Kubra ... The word Sahara desert which means in Arabic means in all languages ​​the great African desert. But the name Tiniri (or Ténéré) which means desert in language Tamashek , the language Tamazight Tuareg native, was awarded by them in one of the driest regions of the Sahara in northern Niger . This great desert is the largest and the only true desert in the geographical sense because it has hyper regions (less than 50 mm of annual rainfall but with extreme interannual irregularity), dry (less than 150 mm annual rainfall and concentrated vegetation in wadis), semi-arid and dry sub-humid areas. Dry diagonal which it belongs includes the Sahara, the Arabian , the Syrian desert (Syria, Jordan and Iraq), the Dasht-e Kavir (Iran), the Dasht-e Lut (Iran), the Thar (India) and continues with medium latitude deserts of Central Asia (the Karakum the Kyzyl Kum and China the Taklamakan desert and Gobi ). This dryness is due to the loss of two major sources of precipitation: the polar front and the equatorial currents from west and it leads to particularly important drought intensity and duration. The Sahara is the largest and the largest hot desert in the world. The climate ranges from the extreme heat in full summer day and cool nights in winter or cold in the highlands (the night the temperature can drop to - 10 ° C in Atakor and in the Assekrem between 2000 and 2500 meters above sea level between December and February). This desert is known for its climate extremes: in fact the Sahara has places belonging warmer, drier, more arid and sunnier in the world. The Sahara obviously has a hot desert climate ( Köppen climate classification BWh) characterized by generally long summers, prolonged and extremely hot or hot while winters are short, brief and extremely gentle and can even be really hot. The Saharan climate is also characterized by a perpetual clear skies and very low rainfall or almost nonexistent, but they are also very irregular and sporadic. Although located predominantly in the Tropic of Cancer , its climate is subtropical said in reference to the subtropical high pressures that are largely responsible for the climate of the Sahara. The northern fringe of the Sahara is subjected to a regime of winter but very low rainfall where the Mediterranean disturbances associated with the polar front reach highly attenuated. The southern edge is subjected to a regime of irregular summer rains but relatively low that only occur when the intertropical convergence zone goes back far enough to the north or when tropical depressions are strong enough. In both cases, the climate is very dry and the rains are very irregular, especially in the southern fringe, on the border with the Sahel . Between the two parties, the central Sahara is subject to extremely arid regime marked by the establishment of the continental trade wind called harmattan (hot wind, very dry and often dusty). Only the highest peaks of the Hoggar and Tibesti are watered but rainfall still remain very low. Finally the Atlantic coastal area bathed by the cold current of the Canaries is subject to sea breezes and a few mists phenomena. Saharan climates, especially subtropical have daily and annual temperature ranges with well marked in some cases of sudden temperature changes due to the extremely dry and clear air and the light of heaven. Moreover, the presence of winds in the desert further increases drought by allowing the renewal of an increasingly dry air mass. In all cases, the Saharan climate is very monotonous, marked by oppressive conditions, because it is hot, dry, sunny and windy throughout the year.

• published: 07 Mar 2015
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