Why specifically does the Northern part of Africa have desert land? I’m assuming it’s on the same geographical level as other countries that have no desert at all?
In: Physics
Climate is much more than just latitude
Things like altitude, geography, air currents, water currents, all of that factors in.
England for example is at the same latitude as parts of Canada that are covered in snow much of the year, yet England has a much milder climate. This is because the north Atlantic ocean current drives warm water and subsequently warm air right to the British isles.
As for the Sahara it is believed that northern Africa regularly went through periods of humidity where it rained a lot and there were lakes and rivers and forests full of life, and periods where the air was dry and all the water dried up and everything died. This was caused by small changes in the planets tilt on its axis. Then at some point some factor changed in this sensitive balance that threw the whole system out of whack.
Current thinking is that this coincides with the spread of humans and agriculture across africa. As northern africa was transitioning from a humid period to a dry period humans transitioned from hunter-gatherer to domesticated animals and farming in order to survive which could have lead to over grazing, over farming and destruction of vegetation. This vegetation would have been needed to provide the moisture in the air to trigger a new humid phase when the time came. Without it the next humid phase was never triggered and the system spiralled out of control leading to the eventual creation of the Sahara desert.
I may be wrong here, but winds at that latitude blow east to west. Where they’re carrying moisture from an ocean, the land will be wetter than where they’re far from the ocean. North Africa has a lot of land between it and the nearest ocean to the east, so it is dry.
You don’t have to assume you can look at a map. Most areas around the same latitude as northern Africa have similar climates, with exceptions being parts of Asia and the eastern United States, and some bits of Mexico. It’s essentially a giant open area of land without many rivers or any sources of water to make it lush.
Also I’m no expert but wind and ocean currents would be a big factor.
The Atlas Mountains block a lot of the wet wind coming in from the Northeast end of the continent. This leads to the Sahara as we know it
The horse latitudes/Hadley Cell typically result in dry climates around °30N and °30S (e.g. the Sahara, Atacama, Kalahari, Sonora, Australia, etc.). Some places around these latitudes on eastern coasts get warm, humid air brought to them from the tropics by ocean currents, however, resulting in lusher, humid climates (e.g. Southeastern USA, Southern China and Japan, Eastern South America, etc.).
Desert regions are mid latitudes, about 30 degrees from equator both, north and South and towards the west of land masses. The Sahara is lined up with the American deserts Sonoran and Chihuahua. The Mohave and great basin deserts also in America is lined up with Gobi and Turkestan desert. Australian desert lines up with Namib and Chilean desert.
This happens because sunlight warms the air at the equator, causing it to rise. As air rises away from the Earth, it cools.
Cool air can’t hold as much water as warm air, so this air has to start getting rid of the water it is carrying. Rain clouds form above the equator and then pour down rain, this creates the tropics.
The cool air has dumped most of it’s rain, so what is left is cool dry air, that moves away from the equator and as it sinks it warms up again. The warm air can hold more moisture so the dry are starts to pull moisture from the land through evaporation which causes the deserts.
Also Africa is not a single country.
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