It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains.
To the south, it is bounded by the Sahela belt of semi-arid tropical savanna around the Niger River valley and the Sudan Region of Sub-Saharan Africa. The Sahara can be divided into several regions including: It is one of three distinct physiographic provinces of the African massive physiographic division. The highest peak in the Sahara is Emi Koussia shield volcano in the Tibesti range of northern Chad.
The central Sahara is hyperaridwith sparse vegetation.
The northern and here reaches of the desert, along with the highlands, have areas of sparse grassland and desert shrubwith trees and taller shrubs in wadiswhere moisture collects.
In the central, hyperarid region, there are many subdivisions of the great desert: These extremely arid areas often receive no rain for years. To the north, the Sahara skirts the Mediterranean Sea in Egypt and portions of Libya, but in Cyrenaica and the Maghrebthe Sahara borders the Mediterranean forest, woodland, and scrub eco-regions of northern Africa, all of which have a Mediterranean climate characterized by hot summers and go here and rainy winters.
According to the botanical criteria of Frank White  and geographer Robert Capot-Rey,   the northern limit of the Sahara corresponds to the northern limit of date palm cultivation and the southern limit of the range of espartoa grass typical of the Snowfall To Rainfall Essay climate portion of the Maghreb and Iberia.
To the south, the Sahara is bounded by the Sahel, a belt of dry tropical savanna with a summer rainy season that extends across Africa from east to west.
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The southern limit of the Sahara is indicated botanically by the southern limit of Cornulaca monacantha a drought-tolerant member of the Chenopodiaceaeor northern limit of Cenchrus biflorusa grass typical of the Sahel.
The Sahara is the world's largest low-latitude hot desert. The area is located in the horse latitudes under the subtropical ridgea significant belt of semi-permanent subtropical warm-core high pressure where the air from upper levels of the troposphere tends to sink towards the ground.
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This steady descending airflow causes a warming and a drying effect in the upper troposphere. The sinking air prevents evaporating water from rising and, therefore, prevents the adiabatic cooling, which makes cloud formation extremely difficult to nearly impossible. The permanent dissolution of clouds allows unhindered light and thermal radiation.
The stability of the atmosphere above the desert prevents any convective overturning, thus making rainfall virtually non-existent. As a consequence, the weather tends to be sunny, dry and stable with a minimal risk of rainfall.
Subsiding, diverging, dry air masses associated with subtropical high-pressure systems are extremely unfavorable Snowfall To Rainfall Essay the development of convectional showers. The lowering of air is the strongest and the most effective over Diabetes Mellitus Type 2 Essays eastern part of the Great Snowfall To Rainfall Essayin the Libyan Desert which is the sunniest, driest and the most nearly "rain-less" place on the planet rivaling the Atacama Desertlying in Chile and Peru.
The rainfall inhibition and the dissipation of cloud cover are most accentuated over the eastern section of the Sahara rather than the western. The prevailing air mass lying above the Sahara is the continental tropical cT air mass, which is hot and dry. Hot, dry air masses primarily form over the North-African desert from the heating of the vast continental land area, and it affects the whole desert during most of the year. Because of this extreme heating process, a thermal low is usually noticed near the surface, and is the strongest and the most developed during the summertime.
The Sahara High represents the eastern continental extension of the Azores High[ citation needed ] centered over the North Atlantic Ocean. The subsidence of the Sahara High nearly reaches the ground during the coolest part of the year while Snowfall To Rainfall Essay is confined to the upper troposphere during the hottest periods.
The effects of local surface low pressure are extremely limited because upper-level subsidence still continues to block any form of air ascent. Also, to be protected against rain-bearing weather systems by the atmospheric circulation itself, the desert is made even drier by his geographical configuration and location. Indeed, the extreme aridity of the Sahara can not be only explained by the subtropical high pressure. The Atlas Mountainsfound in Algeria, Morocco and Tunisia also help to enhance the aridity of the northern part of the desert.
These major mountain ranges act as a barrier causing a strong rain shadow effect on the leeward side by dropping much of the humidity brought by atmospheric disturbances along the polar front which affects the surrounding Mediterranean climates.
The primary source of rain in the Sahara is the Intertropical Convergence Zonea continuous belt of low-pressure systems near the equator which bring the brief, short and irregular rainy season to the Sahel and southern Sahara. Rainfall in this giant desert has to overcome the physical and atmospheric learn more here that normally prevent the production of precipitation.
The harsh climate of the Sahara is characterized by: The sky is usually clear above the desert and the sunshine duration is extremely high everywhere in the Sahara.
The highest values are very close to the theoretical maximum value. The Sahara has a huge potential for solar energy production. The constantly high position of the sun, the extremely low relative humidity, and the lack of vegetation and rainfall make the Great Desert the hottest continuously large area worldwide, and the hottest place on Earth during Snowfall To Rainfall Essay in some spots.
Salah, well known in Algeria for its extreme heat, has average high temperatures of There are even hotter spots in the Sahara, but they are located in extremely remote areas, especially in the Azalailying in northern Mali.
Some examples of this are: BilmaNiger and Faya-Largeau, Chad. Sand and ground temperatures are even more extreme. Due to lack of cloud cover and very low humidity, the desert usually features high diurnal temperature variations between days and nights.
However, it is a myth that Snowfall To Rainfall Essay nights are cold after extremely hot days in the Sahara. Still, it is true that winter nights can be cold as it can drop to the freezing point and even below, especially in high-elevation areas. The frequency of subfreezing winter nights in the Sahara is strongly influenced by the North Atlantic Oscillation NAOwith warmer winter temperatures during negative NAO events and cooler winters with more frosts when the NAO is positive.
The average annual rainfall ranges from very low in the northern and southern fringes of the desert to nearly non-existent over the central and the eastern part. For example, BiskraAlgeria and OuarzazateMorocco are found in this zone. For example, Timbuktu, Mali and AgadezNiger are found in this zone.
The vast central hyper-arid core of the desert is virtually never affected by northerly or southerly atmospheric disturbances and permanently remains under the influence of the strongest anticyclonic weather regime, and the annual average rainfall can drop to less than 1 millimetre 0.
Just click for source fact, most of the Sahara receives less than 20 millimetres 0. However, at Snowfall To Rainfall Essay two instances of snowfall have been recorded in Sahara, in February and Decemberboth in the town of Ain Sefra.
The Sahara comprises several distinct ecoregions. With their variations in temperature, rainfall, elevation, and soil, these regions harbor distinct communities of plants and animals. The Atlantic coastal desert is a narrow strip along the Atlantic coast where fog generated offshore by the cool Canary Current provides sufficient moisture to sustain a variety of lichenssucculentsand shrubs. The North Saharan steppe and woodlands is along the northern desert, next to the Mediterranean forests, woodlands, and scrub ecoregions of the northern Maghreb and Cyrenaica.
Winter rains sustain shrublands and dry woodlands that form a transition between the Mediterranean climate regions to the north and the hyper-arid Sahara proper to the south. The Sahara Desert ecoregion covers the hyper-arid central portion of the Sahara where rainfall is minimal and sporadic. Vegetation is rare, and this ecoregion consists mostly of sand dunes erg, chech, raouistone plateaus hamadasgravel plains regdry valleys wadisand salt flats.
The South Saharan steppe and woodlands ecoregion is a narrow band running east and west between the hyper-arid Sahara and the Sahel savannas to the south.
These rains sustain summer pastures of grasses and herbs, with dry woodlands and shrublands along seasonal watercourses. In the West Saharan montane xeric woodlandsseveral volcanic highlands provide a cooler, moister environment that supports Saharo-Mediterranean woodlands and shrublands. Higher and more regular rainfall and cooler temperatures support woodlands and shrublands of Date palm, acaciasmyrtleoleandertamarixand several rare and Snowfall To Rainfall Essay plants.
The Saharan halophytics is an area of seasonally flooded saline depressions which is home to halophytic salt-adapted plant communities. The Tanezrouft is one of the harshest regions on Earth as well as one of the hottest and driest parts of the Sahara, with no vegetation and very little life. It is along the borders of Algeria, Niger]] and Mali, west of the Hoggar mountains. The flora of the Sahara is highly diversified based on the bio-geographical characteristics of this vast desert.
Floristicallythe Sahara has three zones based on the amount of rainfall received — the Northern MediterraneanCentral and Southern Zones. There are two transitional zones — the Mediterranean-Sahara transition and the Sahel transition zone.
The Saharan flora comprises around species of vascular plants. Approximately a quarter Snowfall To Rainfall Essay these are endemic. About half of these species are common to the flora of go here Arabian deserts. The central Sahara is estimated to include five hundred species of plants, which is extremely low considering the huge extent of the area.
Plants such as acacia trees, palms, succulents, spiny shrubs, and grasses have adapted to the arid conditions, by growing lower to avoid water loss by strong winds, by storing water in their thick stems to use it in dry periods, by having long roots that travel horizontally to reach the maximum area of water and to find any surface moisture, and by having small thick leaves or needles to prevent water loss by evapotranspiration.
Plant leaves may dry out totally and then recover. Several species of fox live in the Sahara including: The addaxa large source antelopecan go nearly a year in the desert without drinking.
The dorcas gazelle is a north African gazelle that can also go for a long time without water. Other notable gazelles include the rhim gazelle and dama gazelle. There remain fewer than mature cheetahs, which are very cautious, fleeing any human presence.
The cheetah avoids the sun from April to October, seeking the shelter of shrubs such as balanites and acacias. They are unusually pale. However, Snowfall To Rainfall Essay is currently extinct in the wild in Egypt and Libya. There are approximately mature individuals left in the wild. Other animals include the monitor lizardshyraxsand vipersand small populations of African wild dog in perhaps only 14 countries  and red-necked ostrich.
Other animals exist in the Sahara birds in particular such as African silverbill and black-faced firefinchhttp://cocktail24.info/blog/pay-to-get-top-argumentative-essay.php others.
There are also small desert crocodiles in Mauritania and the Ennedi Plateau of Chad. Its venom contains large amounts of agitoxin and scyllatoxin and is very dangerous; however, a sting from this scorpion rarely kills a healthy adult. The Saharan silver ant is unique in that due to the extreme high temperatures of their habitat, and the threat of predators, the ants are active outside their nest for only about ten minutes per day. Dromedary camels and goats are the domesticated animals most commonly found in the Sahara.
Because of its qualities of endurance and speed, the dromedary is the favourite animal used by nomads. Human activities are more Snowfall To Rainfall Essay to affect the habitat in areas of permanent water oases or where water comes close to the surface.
Here, the local pressure on natural resources can be intense. The remaining populations of large mammals have been greatly reduced by hunting for food and recreation. In recent years development projects have started in the deserts of Algeria and Tunisia using irrigated water pumped from underground aquifers. These schemes often lead to soil degradation and salinization.