KHAMSIN, SIROCCO, SHAHALI AND SHIMOOM

Sahara desert from space
Source Cropped from Image:
Africa satellite plane
Date February 11, 2002
Author NASA
From Wikipedia, the free encyclopedia

The Sahara Desert, covering most of North Africa, is the largest desert in the world. From north to south the Sahara is between 800 and 1,200 miles and is at least 3,000 miles (4,800 km) from east to west. Due to the massive size of the Sahara, Africa is split into two regions: that which lies above or forms part of the Sahara and the rest of Africa south of the Sahara. On the west, the Sahara is bordered by the Atlantic Ocean and on the east by the Red Sea, and to the north are the Atlas Mountains and Mediterranean Sea.
(© Copyright 1998, ThinkQuest team 16645)
The only true desert to be found along the 0° meridian line also happens to be world's largest. The Sahara covers most of north Africa, more than a third of the continent, and an area around the same size as the United States. It is a desert of extraordinary variety. Temperatures in excess of 55° C have been recorded in parts of Libya, while in some places frost can be seen during the winter. All the standard desert landscape types are present in the Sahara, from great fields of shifting sand dunes or ergs, to vast plains filled with rocks, known as reg.
Rainfall in most parts of the Sahara is scant and erratic - some areas endure several years without even a hint of a shower. In common with other desert regions, storms in the Sahara can be extremely localised, often affecting an area as small as 20 square kilometres. Strong, unpredictable winds are typical of the Saharan weather systems, and these have come to be known by names such as khamsin (50 days), sirocco, shahali, and simoom. These winds can blow for days on end, bringing with them vast amounts of dust and sand, which cover everything in their path and reduce visibility close to zero. From time to time, particularly powerful sandstorms can be extremely unpleasant and dangerous for anyone caught in them. Dust devils, which are like whirlwinds, also occur, hurling sand, dust, small animals and plants into the air.
(From oxfam.org.uk)

Enlarge the World Desert Map
Image by USGS
© 2005-2009 Geology.com.

The Sahara (Arabic: الصحراء الكبرى‎, aṣ-ṣaḥrā´ al-kubra, "The Greatest Desert") is the third-largest desert on Earth after Antarctica and the Arctic, and it is the world's largest hot desert. At over 9,000,000 square kilometers (3,500,000 sq mi), it covers most of Northern Africa, making it almost as large as the continent of Europe. The desert stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean. To the south, it is delimited by the Sahel: a belt of semi-arid tropical savanna separating the Sahara from Sub-Saharan Africa.
The Sahara covers huge parts of Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, Sudan and Tunisia. It is one of three distinct physiographic provinces of the African massive physiographic division.
Several deeply dissected mountains and mountain ranges, many volcanic, rise from the desert, including the Aïr Mountains, Ahaggar Mountains, Saharan Atlas, Tibesti Mountains, Adrar des Iforas, and Red Sea Hills. The highest peak in the Sahara is Emi Koussi, a shield volcano in the Tibesti range of northern Chad.
Most of the rivers and streams in the Sahara are seasonal or intermittent, the chief exception being the Nile River, which crosses the desert from its origins in central Africa to empty into the Mediterranean. Underground aquifers sometimes reach the surface, forming oases, including the Bahariya, Ghardaïa, Timimoun, Kufrah, and Siwah.
(From Wikipedia, the free encyclopedia)

Biggest deserts
NASA World Wind 1.4 used.
From Wikipedia, the free encyclopedia

Antarctica 6400px from Blue Marble
A satellite composite image of Antarctica
From Wikipedia, the free encyclopedia

Satellite image of the Arctic surface
Artificially coloured topographical map
From Wikipedia, the free encyclopedia

A composed satellite photograph of Africa
Orthographic projection
NASA "Blue Marble" image
Art of Illusion program
From Wikipedia, the free encyclopedia

Eilat and the Red Sea with Jordan on the other side.
Date 2007-01-26 (original upload date)
Author Photo by beivushtang
Original uploader Beivushtang at en.wikipedia

Map of the Mediterranean Sea
ISO 3166-1 Alpha-3 code
Raster background map
Screenshot from NASA World Wind
Date June 2007
Author Eric Gaba (Sting)
From Wikipedia, the free encyclopedia

The Oasis of Timia
Photo by Denver Maxwell
Source Transferred from en.wikipedia
Original upload date 2006-11-05
Author Original uploader Denvermaxwell at en.wikipedia

Area of Hoggar (Tamanghasset, Algeria)
Originally posted to Flickr as Algerien_1_0050
Date April 15, 2006
Author Gruban/Patrick Gruban, Munich, Germany

Location of the Atlas Mountains (colored red)
North Africa
From Wikipedia, the free encyclopedia

Panoramic view of typical Berber village
(Morocco - High Atlas Mountains)
From Wikipedia, the free encyclopedia

Valley in Atlas mountain, Morocco
From Wikipedia, the free encyclopedia

Panoramic picture
The artificial lake of Lalla Takerkoust
Barrage Cavagnac, Central Morocco
The hydroelectric dam (extreme right)

The highest peak in the Sahara
Emi Koussi
South end of Tibesti Mountains
Source spaceflight.nasa.gov
Date December 2001
From Wikipedia, the free encyclopedia

The vertical stabilizer of the Space Shuttle Endeavour almost appears to point out Emi Koussi Volcano in the Tibesti Mountains of Chad in Saharan Africa. Emi Koussi is one of the prominent volcanoes within the Tibesti massif of north-central Africa. The dark, shield-shaped volcanic edifice has developed over a mantle hot spot that rises beneath this region of the African continent.

Vegetation along the Nile
The river next to the big city, Beni Suef
Right side at the bottom of the picture
Date 18th Juny 2003 "12:38"
Author Marcell Katona
From Wikipedia, the free encyclopedia

Dhows traversing the Nile near Aswan
Date 7 May 2008
Author Jordan Busson
From Wikipedia, the free encyclopedia

Ubari Oasis in Libya
Date 17.05.2005
Author Sfivat
From Wikipedia, the free encyclopedia

bahariya oasis spotted from black mountain
Feb 9, 2005
Photo: nomo/michael hoefner at zwo5.de
From Wikipedia, the free encyclopedia

Kufra Oasis, Libya
Cultivated areas and irrigation circles
From SPOT satellite
Source earthobservatory.nasa.gov
(Earth Observatory)
Date 6-10-207
Author NASA
From Wikipedia, the free encyclopedia

Panoramic view of Siwa Oasis 2006
Northwest Egypt
Overlooking ancient fortress made of mud-bricks
Photo Source cortinastelle.it
Transferred from wikipedia
Original upload date 2007-01-30

Look at a map of North Africa from Egypt to Algeria. Almost everything outside the Nile Valley and south of the coastal plain appears to be lifeless sand and gravel deserts, spotted here and there with oases and rain-catching massifs of uplifted bedrock. But peer deeper, under the sand, and you will find water.
Under the Sahara lie three major aquifers, strata of saturated sandstones and limestones that hold water in their pores like a wet sponge. The easternmost of these, extending over two million square kilometers, underlies all of Egypt west of the Nile, all of eastern Libya, and much of northern Chad and Sudan, and contains 375,000 cubic kilometers of water—the equivalent of 3750 years of Nile River flow.
(From saudiaramcoworld.com)
Its parched, forbidding landscape took shape over thousands of years, but even today, the Sahara is constantly changing.
Why is this desert so important to Africans? How do people survive its harsh, dry climate? And is the Sahara getting bigger, or smaller?
By studying satellite photos, some scientists have come to believe that the Sahara regularly shrinks and grows. In the early 1980s, the Sahara's southern edge expanded into the Sahel, a dry band that separates the desert from the savanna. But by the mid-1980s this area was green and wet again.
(From calacademy.org)