Coriolis Effect

Coriolis Effect explains the pattern of deflection preferred by objects not firmly connected to the ground as they travel long distances around the Earth. The Coriolis Effect is responsible for many large-scale weather patterns. French engineer-mathematician Gustave-Gaspard Coriolis described the Coriolis effect in 1835.

Table of Contents

What is the Coriolis Effect?

The Coriolis Effect is an apparent effect produced by a rotating frame of reference. The effect occurs when an object moving along a straight path is viewed from a non-fixed frame of reference. The moving frame of reference is the Earth which rotates at a fixed speed. Therefore, when an object moving in a straight path is viewed from Earth, it appears to lose its course because of Earth’s rotation.

Short Summary of Coriolis Effect
Simply put, the Coriolis effect makes planes and air currents that travel long distances around the earth appear to move at a curve instead of a straight line.

What is Coriolis Force?

Coriolis force is the invisible force that appears to deflect the objects. The Coriolis force is determined by the object’s rate of rotation and mass of the object.

Coriolis Effect on Earth

Coriolis force is perpendicular to the object’s axis. As the Earth spins on its axis from west to east, the Coriolis force acts north-south. At the Equator, the Coriolis force is zero.

What causes Coriolis Effect?

The key to the Coriolis Effect lies in Earth’s rotation. The earth rotates faster at the equator than it does at the poles. Earth being wider at the equator, the equatorial regions race nearly 1,600 kilometres per hour. At the poles, the earth rotates at a rate of 0.00008 kilometres per hour.

Read More: Earth’s Rotation

Demonstration of Coriolis Effect

Let us pretend to be standing at the North Pole and tossing a ball to our friend standing at the equator. While the ball travels through the air, the Earth below it is rotating. Hence, when the ball reaches the equator, it lands in a location somewhere to the west of where you were aiming. The figure below illustrates this example.

Coriolis Effect

Near the earth’s surface, the Coriolis effect creates wind (and water) patterns that move to the east toward the equator and to the west toward the poles. These prevailing wind patterns are responsible for moving clouds around the globe and, thus, creating weather patterns in different regions.

A ball’s movement across a rotating merry-go-round shown in the video is a helpful demonstration of the Coriolis force.

Characteristics of Coriolis Effect

The Coriolis effect characteristics can be summarised as follows:

  • Coriolis force is a fictitious force resulting from the rotational movement of the earth.
  • Coriolis effect is effective on objects that are in motion such as wind, aircraft, ballistic and flying birds.
  • Coriolis effect only affects the wind direction and not the wind speed as it deflects the wind direction from the expected path.
  • The magnitude of Coriolis force is determined by wind speed. The higher the wind speed, the greater the deflection.
  • Coriolis effect is maximum at the poles and zero at the equator.
  • Coriolis force always acts in a direction that is perpendicular to the moving object’s axis.

How are weather patterns affected by the Coriolis Effect?

The development of weather patterns, such as cyclones and trade winds, are examples of the impact of the Coriolis Effect.

In the Northern Hemisphere, fluids from high-pressure systems pass low-pressure systems to their right. As air masses are pulled into cyclones from all directions, they are deflected, and the storm system, a hurricane, seems to rotate counter-clockwise.

In the Southern Hemisphere, currents are deflected to the left. As a result, storm systems seem to rotate clockwise.

Did you know?
The Coriolis force is strongest at the poles and absent at the equator, and Cyclones need Coriolis force to circulate. Hence, hurricanes never occur in equatorial regions and never cross the Equator.

Coriolis Effect and Ocean Current

Ocean currents are the continuous, directional and predictable movement of seawater. Ocean currents are driven by the movement of wind across the ocean’s waters, and the Coriolis effect dramatically affects the direction of the ocean’s currents. Many of the ocean’s most enormous currents circulate in warm, high-pressure areas called gyres, and the Coriolis effect creates the spiralling pattern in these gyres./p>

Impact of Coriolis Effect on Airplanes and Human Activity

Fast-moving objects impacted by weather, such as aeroplanes and rockets, are influenced by the Coriolis Effect. The Coriolis Effect largely determines the direction of the prevailing winds. Hence a pilot must take this into account while charting routes for long-distance travel.

Military snipers consider the Coriolis effect. Although bullets’ trajectory is minimal to be significantly affected by the Earth’s rotation, sniper targeting is so precise that a deflection of several centimetres could injure innocent people or damage civilian infrastructure.

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Frequently Asked Questions – FAQs


What is the Coriolis effect in simple terms?

In simple terms, the Coriolis Effect makes things travelling long distances around the Earth appear to move at a curve instead of a straight line.

How does the Coriolis effect affect the wind?

The Coriolis effect affects the wind by deflecting its path to the right in the Northern hemisphere and the left in the Southern hemisphere.

Where is the Coriolis effect the strongest?

The Coriolis effect is strongest near the poles and is absent at the equator.

Why does the Coriolis effect not occur at the equator?

Underneath a horizontally and freely moving object at the equator, there is no turning of the surface of the Earth. As a result, there is no curving of the object’s path relative to the Earth’s surface.

Do Coriolis force affect snipers?

Yes, Coriolis force affects snipers. If the target is westerly, the bullet will shoot low, and if the target is easterly, the bullet will land higher than the shooter aimed.

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  1. Does coriolis force affect vertical movement of air ?