Physical Geography 101
Global Wind Patterns
Scales of Motion: size and duration
Ideal Global Wind Patterns
Start with an ideal globe model - no surface features, no seasons
Major Global Wind Belts
Intertropical Convergence Zone (ITC)
Subtropical High Pressure Belt
Hadley Cell Circulation
Ferrel Cell Circulation
Polar Cell Circulation
Class Discussion of Actual Global Wind Patterns
January Global and Polar Wind Map
July Global and Polar Wind Map
Monsoons in Southern and Southeastern Asia: 3 factors.
1) Location and size of the Himalaya Mountains
2) Location of the Indian Ocean
3) extreme movement of the ITC in Asia - no similar shifts occur elsewhere in the world
- results in a reversal of wind direction between summer and winter.
In January, the wind direction is from the northeast, out of the Siberian High pressure center
- this is cold, very dry air.
This cold, dry air runs into the Himalayas.
What happens to it? Think in terms of orographic precipitation.
In July, the air mass is coming from the Indian Ocean, a southwest wind - this is very warm, very moist air.
This warm, moist air runs into the Himalayas. What happens to it?
1) Sea-Land breezes
2) Mountain winds - mountain barriers cause variable wind directions, updrafts and downdrafts are common
3) Drainage winds - cold air flows downward often following valleys
4) Chinook winds - warm, dry, leeward winds associated with the orographic precipitation process.