1. Section 2: Atmospheric Phenomena
UNIT 1 - EARTH AS A SYSTEM
Section 2: Atmospheric Phenomena

2. CORIOLIS EFFECT
Due to earth’s rotation, winds heading due North or South are deflected from their straight path.
Northern Hemisphere: deflect to the right
Southern Hemisphere: deflect to the left

3. PRESSURE GRADIENTS
Differences in pressure among areas of the atmosphere lead to differences in weather.

4. EARTH’S ATMOSPHERE IS DIVIDED INTO “CELLS”
Hadley Cell Animation

5. Cold,
dry air
falls
Polar Cell
Moist air rises — rain
Polar cap
Ferrel Cell
Arctic tundra
Evergreen
coniferous forest
60°
Cool, dry
air falls
Temperate deciduous
forest and grassland
30°
Desert
Hadley Cell
Tropical deciduous forest
Moist air rises,
cools, and releases
Moisture as rain 0°
Equator
Tropical
rain forest
Tropical deciduous forest
30°
Desert
Hadley Cell
Temperate deciduous
forest and grassland
Cool, dry
air falls
60°
Ferrel Cell
Polar cap
Cold,
dry air
falls
Moist air rises — rain
Polar Cell

6. EL NIÑO – SOUTHERN OSCILLATION
Periodic shift in climate on a large scale
Unknown cause, but driven by changes in pressure; occurs every several years (varies)
Trade winds slow, causing warm water that is normally focused in the western Pacific to flow back to the east.
This slows upwelling off the coast of N. and S. America, devastating fisheries and increasing precipitation
Often followed by the reversing of this trend (La Nina – STRONGER than usual trade winds)
Most devastating in recent history: 1997/1998

7. THE START OF AN EL NIÑO

8. MOST RECENT EL NIÑO CONDITIONS