How the Trade Winds Are Formed

The trade winds are formed by circular wind patterns around the equator. The regions around the equator are typically hotter than other places around the world and the stretch of ocean along the equator is no different. The air along the equator is hot and rises high into the atmosphere where it travels north and south toward the poles. In the Northern Hemisphere, warm air travels north. In the Southern Hemisphere, it travels south. As the air travels toward the poles, it cools down and descends. The now-cooler air is attracted to the low-pressure system and blows back toward the equator.

The Coriolis Effect

Since a north-to-south wind pattern wouldn’t help global travelers, something needs to push the winds westward. That’s where the Coriolis effect comes in. The Coriolis effect has to do with the rotation of the Earth. Due to our planet's roundness, things along the equator spin much faster than things on the poles. To be more precise, things at the equator spin about 1,000 miles per hour, while the poles rotate only 0.00005 miles per hour.

Since wind isn’t connected to the ground, the Earth rotates under it. Within the subtropical regions, the easterly rotation of the Earth is so fast that it makes the wind seem like it’s blowing toward the west. The circular wind patterns coupled with the spinning of the Earth is what creates the easterly trade winds (that blow from east to west).