Britannica Sources used in this answer

How does Earth’s rotation affect the direction of winds?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Wispy cirrus clouds stretch across a bright blue sky above trees and a river at Pinawa Dam Provincial Park in Manitoba, Canada, with sunlight illuminating the scene. — Atmosphere The atmospheres of planets in the solar system are composed of various gases, particulates, and liquids. They are also dynamic places that redistribute heat and other forms of energy. On Earth, the atmosphere provides critical ingredients for living things. Here, feathery cirrus clouds drift across the deep blue sky over Pinawa Dam Provincial Park, near Pinawa, Manitoba, Canada.

Earth’s rotation significantly influences wind direction through an apparent force known as the Coriolis force. Because Earth rotates from west to east, an observer on the ground perceives a deflection of moving air that would otherwise travel in a straight line relative to a fixed point in space.1234

This deflection follows a consistent pattern based on the hemisphere:
* Northern Hemisphere: Moving air is deflected to the right of its intended path.134
* Southern Hemisphere: Moving air is deflected to the left of its intended path.134

This effect is fundamental to geostrophic motion, where the Coriolis force balances the pressure-gradient force, causing winds to blow parallel to isobars rather than directly from high to low pressure. Consequently, air rotates counterclockwise around large-scale low-pressure systems and clockwise around high-pressure systems in the Northern Hemisphere, with the reverse occurring in the Southern Hemisphere. Near the Equator, where the Coriolis force is weakest, this deflection is minimal, and winds tend to blow more directly toward low pressure.243