Definition
Persistent surface winds in the tropics that blow from the subtropical high-pressure belts toward the equatorial low-pressure belt. In the Northern Hemisphere they blow from the northeast; in the Southern Hemisphere they blow from the southeast. The deflection from a straight north-south flow is caused by Coriolis force.
Plain English
Steady winds near the equator that blow in a fairly reliable direction year-round. North of the equator they come from the northeast, and south of the equator they come from the southeast.
Context Anchor
Seen in weather and global wind-circulation discussions, especially when studying how Earth’s rotation changes wind direction.
Derivation
The name comes from an old English meaning of 'trade' — 'a regular path or track.' Sailing ships relied on these dependable winds to follow regular trade routes across the oceans, which is how the winds came to be called 'trade winds.' The connection to commerce came later.
Why Pilots Care
These consistent winds affect routing, fuel burn, and flight times on transoceanic trips in the tropics.
Grounding Statement
Air flowing from the subtropics toward the equator gets bent sideways by Earth's rotation, producing a steady slanted wind rather than a straight north-south flow.
Intuition Check
Trade winds are not winds caused by business or commerce. In aviation weather, the term means a regular tropical wind pattern shaped by pressure areas and Earth’s rotation.
Example Sentence 1
The instructor used the trade winds to illustrate how Coriolis force deflects moving air to the right in the Northern Hemisphere.
Example Sentence 2
South of the equator, the southeasterly trade winds pushed the aircraft slightly off the great-circle route.