Question

Distinguish between westerlies and trade winds

Answer 1

Short answer
- Trade winds: steady easterly winds (from the northeast in the Northern Hemisphere, from the southeast in the Southern Hemisphere) that blow toward the equator from roughly 0°–30° latitude.
- Westerlies: mid-latitude winds that blow from the west toward the east, typically between about 30°–60° latitude in both hemispheres.

Key differences
- Latitude and direction
- Trades: 0°–30°; blow toward the equator from the northeast (NH) or southeast (SH).
- Westerlies: 30°–60°; blow poleward and eastward (from the west).
- Atmospheric cell association
- Trades: produced by the Hadley cell (air rises near the equator and returns equatorward at the surface from the subtropical highs).
- Westerlies: produced by the Ferrel cell (air flows poleward at the surface from the subtropical highs toward the subpolar lows).
- Cause (Coriolis effect)
- Both are deflected by the Coriolis force: trades are deflected toward the west (become NE/SE), westerlies are deflected toward the east.
- Variability and strength
- Trades: generally steadier and more consistent year‑round.
- Westerlies: more variable and stronger in winter; drive mid‑latitude storm tracks.
- Weather and climate roles
- Trades: strongly influence tropical rainfall patterns and the ITCZ; drive equatorial and subtropical ocean currents (westward equatorial currents).
- Westerlies: steer mid‑latitude cyclones and large-scale weather systems; drive eastward ocean currents (e.g., North Atlantic Drift).
- Navigation/History
- Trades: crucial for historical sailing routes to the Americas.
- Westerlies: used by ships returning to Europe and for transoceanic air routes.

Short summary
Trades = steady easterlies in the tropics driven by the Hadley cell and the Coriolis deflection toward the west. Westerlies = variable west-to-east winds in the mid-latitudes driven by the Ferrel cell that carry storms and influence mid-latitude climate and ocean circulation.