Why are Deserts so dry?

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
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
Deserts lie on the West side of continents.
2.
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 E F R A I N F A L L
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.