Wind
Air moving from high pressure to low.
Wind is air flowing from high pressure toward low. The driver is uneven solar heating: the equator receives more energy per unit area than the poles, warm air rises and cool air moves in beneath it. Everything else is detail on that.
Pressure gradient and Coriolis
The steeper the pressure difference over distance, the stronger the wind — which is why tightly packed isobars on a chart mean gales. But wind does not blow straight down the gradient. Earth's rotation deflects it right in the northern hemisphere and left in the southern, the Coriolis effect, so winds circle pressure systems rather than filling them directly.
Global circulation
| Cell | Latitude | Surface winds |
|---|---|---|
| Hadley | 0–30° | Trade winds, blowing toward the equator |
| Ferrel | 30–60° | Westerlies |
| Polar | 60–90° | Polar easterlies |
The descending arm of the Hadley cell at about 30° is why most of the world's hot deserts sit in that band — sinking air warms and dries.
Local winds
Sea breezes blow onshore by day, because land heats faster than water and the rising air over land draws cooler sea air in. At night it reverses, land cooling faster, giving a land breeze. The same mechanism at larger scale drives monsoons.