Coriolis Effect

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The Coriolis Effect describes the turn of the wind to the right in the Northern Hemisphere caused by earth's rotation.

Why do I care?  The Coriolis Effect contributes to the circular motion of the wind around pressure systems which move weather patterns in the southeastern United States.

I should already be familiar withTilt and Latitude

Coriolis Effect
Figure A. Deflection by Coriolis Effect

The Earth rotates at a high speed counter-clockwise as viewed from the North Pole. If an object starts at the North Pole and moves toward the equator in a straight-line path, for example, the object will appear to deflect to the right of its intended path because the earth is rotating under it as it moves. This is called the Coriolis Effect. If the earth did not rotate, an object would continue on a straight-line path without appearing to deflect at all. The amount of deflection varies with latitude, the speed of the object and the rotation of the earth. The deflection is greatest at the poles and decreases to zero at the equator.

The Coriolis Effect can be seen in action in the general circulation of the atmosphere. The winds at all latitudes to the north of 0° deflect to the right of their intended path in the Northern Hemisphere. The Coriolis Effect does not impact the wind speed, only the wind direction. The Coriolis Effect impacts objects on a large scale and does not generally have a big influence on small scale objects at the earth’s surface. Though hurricanes are small scale compared to the overall globe, hurricanes need the Coriolis Effect to help develop the circular motion of their circulations. Tornadoes are not impacted by the Coriolis Effect because they are so small in scale and short in duration. The direction water goes down the drain is also not impacted by the Coriolis Effect.


Want to learn more?

General Circulation of the AtmosphereWhat Drives Weather


Links to National Science Education Standards:

7th grade science: 7.E.1.5 : Explain the influence of convection, global winds, and the jet stream on weather and climatic conditions.


Activities to accompany the information above:

Activity: Renewable Energy: Wind (pdf version of original activity.)

Description: This activity focuses on the relationship between barometric pressure, wind speed and wind direction. Students will use these parameters to analyze surface maps of the United States and form a relationship with the patterns that will show up on the map.

Relationships to topics: PressureWhat Drives WeatherCoriolis EffectGeneral Circulation of the Atmosphere


Activity: Twisting the Air Away: The Coriolis Effect  (Link to original activity.)

Description: This activity focuses on what impacts the coriolis effect has on air movement throughout the atmosphere because of the rotation of the earth and also the impacts the coriolis effect has on ocean currents.

Relationships to topics: Coriolis Effect