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Why are Deserts so dry?.

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Presentation on theme: "Why are Deserts so dry?."— Presentation transcript:

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

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.

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