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Pressure Belts and Wind Systems: Planetary and Local Winds
July 19, 20265 min read
Pressure Belts and Wind Systems: Planetary and Local Winds
Introduction
Atmospheric pressure differences drive wind systems worldwide. The uneven heating of the Earth's surface creates global pressure belts, which in turn generate planetary wind systems - trade winds, westerlies, and polar easterlies. Superimposed on these are seasonal winds (monsoons) and local winds influenced by regional geography.
Factors Affecting Atmospheric Pressure
Key Factors
- Temperature: Warm air expands, rises → low pressure; cold air contracts, sinks → high pressure
- Altitude: Pressure decreases with height; ~half of atmosphere below 5.6 km
- Earth's rotation (Coriolis force): Deflects winds to the right in NH, left in SH
- Water vapour: Humid air is lighter than dry air → lower pressure
Pressure Measurement
- Unit: Millibar (mb) or hectoPascal (hPa)
- Standard sea-level pressure: 1013.25 mb
- Isobars: Lines joining places of equal pressure on maps
Global Pressure Belts
Seven Pressure Belts (Idealized)
| Pressure Belt | Latitude | Characteristic |
|---|---|---|
| Equatorial Low | 0° (5°N-5°S) | Low pressure; high temperature, rising air; doldrums |
| Sub-tropical High | 30° N and S | High pressure; descending air; horse latitudes |
| Sub-polar Low... |
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