1. Why are Deserts so dry?

2. SAHARA DESERT in North Africa
Key places today…
North Africa
Sahara Desert
Atlantic Ocean
Canary Islands
Morocco
Atlas Mountains

3. 1. Deserts are areas of permanent HIGH PRESSURE
Air sinks 1.
Air warms
Moisture evaporates
Clear blue skies and dry weather
High PRESSURE or anticyclone

4. 2. Deserts lie on the West side of continents….
In zones where the prevailing winds come from the east.

5. Saharan sand blown off to the west by easterly winds.

6. 3.
The cold ocean current : THE CANARY CURRENT

7. Canary Islands - fog

8. ‘It was pretty cold and windy in the damp fog’

9. San Francisco coast California –
Also gets fogs.

10. 3.
Moisture condenses out of the air over cold oceans

11. RELIEF RAINFALL and RAIN SHADOW
Atlantic Ocean
Atlas Mountains
Sahara Desert

12. RAIN in Morocco
Sahara Desert
Rain near Equator

13. R E L I F A N

14. Rain Shadow effect here
Sahara Desert Begins
Relief Rainfall Here

15. Warm dry air sinks down into the Sahara…
… making it a desert

16. The Relief Rainfall and the Rain Shadow happens in the dry SW USA too.