Coriolis effect

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Definition of Coriolis effect:
An apparent force that arises because of the earth's spin around its axis. Freely-moving objects are deflected to the right of their direction of motion in the northern hemisphere and to the left of their direction of motion in the southern hemisphere. [1]
This is the common definition for Coriolis effect, other definitions can be discussed in the article


Due to the earth’s rotation, the air mass curves relative to the earth’s surface. In the Northern Hemisphere this effect causes the air to deflect to the right of the direction of the air movement and in the Southern Hemisphere the deflection of the air is to the left of the direction of air movement. This is called the Coriolis effect. Because of the rotating earth, a point at the equator moves faster than a point at higher latitude. Both points make one full rotation at the time of one day, but the point at the equator has to travel a longer distance. For this reason, the point at the equator is moving faster. The air moving north or south away from the equator toward the poles moves faster than the earth beneath it and the air curves relative to the earth’s surface. [2]

Coriolis effect with deflection of the air masses [3]

Ekman spiral

The ekman spiral is a consequence of the coriolis effect. When the surface water moves by the wind, they drag the deeper layers with them. Each layer of water is moved by friction from the shallower layer and each deeper layer moves more slowly than the layer above it. The deflection of the surface current has an angle of 45°. This creates a spiral called the Ekman spiral. At a depth of 100 meters, the water flows in the opposite direction than the surface current. The net water transport is perpendicular (90°) to the initial wind direction and this is the effective direction of the current flow. [4] [5]

Ekman spiral [6]

Further reading

Ocean circulation


  1. Pinet P.R. 1998.Invitation to Oceanography. Jones and Barlett Publishers. p. 508
  2. Karleskint G. 1998. Introduction to marine biology. Harcourt Brace College Publishers. p.378
  3. NOAA
  5. Pinet P.R. 1998.Invitation to Oceanography. Jones and Barlett Publishers. p. 508
  6. NOAA
The main author of this article is TÖPKE, Katrien
Please note that others may also have edited the contents of this article.

Citation: TÖPKE, Katrien (2008): Coriolis effect. Available from [accessed on 19-01-2017]