Global Atmospheric Circulation and Winds

Overview of Atmospheric Cells

Earth's atmospheric circulation is divided into three cells per hemisphere:
- Hadley Cell
- Farrell Cell
- Polar Cell
Global circulation is at an angle due to Earth's rotation.

Earth's rotation causes apparent motion:
- To the right in the Northern Hemisphere
- To the left in the Southern Hemisphere
Key Point: Earth's surface rotates faster at the Equator than at the poles, leading to the Coriolis effect.
Important in explaining wind patterns:
- Winds blow anti-clockwise around low pressure and clockwise around high pressure in the Northern Hemisphere (vice versa in the Southern Hemisphere).

Jet Streams:
- Formed by Coriolis effect and conservation of angular momentum.
- Air moving from the equator speeds up as it approaches the poles.
Subtropical Jet Stream:
- Occurs at 12 to 15 km altitude.
- Associated with strong winds (up to 280 mph).
- Little associated weather due to its position between Hadley and Farrell cells.
Polar Front Jet Stream:
- Occurs at 11 to 13 km altitude.
- Formed at the boundary between cold polar air and warm tropical air (polar front).
- Stronger temperature contrast leads to a stronger jet, especially in winter.

Trade Winds:
- Formed by the surface flow of Hadley cells.
- Air flows towards the equator and is deflected westward.
- Results in Northeast trade winds (Northern Hemisphere) and Southeast trade winds (Southern Hemisphere).
Prevailing Westerlies:
- Occur due to surface winds in the Farrell cells.
- Deflected to the right in the Northern Hemisphere, leading to westerly and southwesterly winds over regions like the UK.

Jupiter has circulation cells similar to Earth due to its fast rotation (day lasts ~9.5 hours).
Strong Coriolis effect due to size and rotation rate.
Multiple alternating bands of rising and falling air create Jupiter's striped appearance.