Coriolis Effect

The Coriolis effect is a fundamental principle that helps explain the movement of air, ocean currents, and other naturally moving objects on Earth and other celestial objects. The effect is also a reason for various weather patterns on Earth. The Coriolis effect was first named after and discovered by a French scientist, Gaspard-Gustave de Coriolis, in 1835. Understanding the effect is essential to grasp the concepts of weather patterns, ocean waves, winds, and the trajectory of missiles and aeroplanes. Here, you can find the Coriolis effect explained in detail to help you better understand this important natural effect of Earth. 

1.0Coriolis Effect Definition

The Coriolis effect is an apparent deflection of the trajectory of an object travelling on the surface of the Earth due to the rotation of the Earth. It is a basic principle in meteorology, oceanography, and even military science. In simple words, objects travelling in a straight line on the surface of the Earth seem to bend because of the planet's rotation. The Coriolis effect causes different directions of wind flow in the northern and southern hemispheres of the Earth. 

In the northern hemisphere, the deflection is to the right side of the object’s original path, while in the southern hemisphere, the direction of its path changes to the left. The Coriolis effect is not a physical force but an apparent force resulting from the rotation of the Earth. Note that the effect is significant only for bodies travelling long distances and at fairly high velocities, e.g., atmospheric winds, ocean currents, and artillery projectiles in long-distance military operations. See the Coriolis effect diagram below to visualise the effect for a better understanding. 

2.0What Causes the Coriolis Effect

The main cause of the Coriolis effect is the rotation of the Earth. However, the main question here is, how does the Earth’s rotation affect the direction of different moving objects on different locations of the Earth? The answer lies in the different latitudes and rational speeds associated with these latitudes. As we know, the Earth rotates from west to east, and this rotational motion results in different rotational speeds at various latitudes. 

If an object is travelling in a straight line over the surface of the Earth, its initial velocity is relative to the rotation of the Earth. Yet the surface of the Earth underneath it is also moving at another velocity. Because the object is travelling from one point to another on a rotating surface, it will be seen to be deflected. This deflection is a function of the speed of the object and the latitude at which it travels. 

This is also the reason why the Coriolis Effect works differently on the Equator and the Poles. 

• At the equator, where Earth's rotational speed is greatest, objects travelling in a straight line seem to curve noticeably to the east (to the right in the Northern Hemisphere, to the left in the Southern Hemisphere).
• At higher latitudes like the poles, this deflection is weaker since the Earth's rotational velocity decreases as it approaches the poles.

3.0Principle of Coriolis Effect

The Coriolis effect is the seeming curving or deflecting of the path of a moving object on the surface of Earth. This occurs due to the rotation of the Earth. But the important point is this: the Coriolis effect is not a force that deflected objects; it's merely how objects moving on Earth will appear to turn while in motion. For example, the objects at different latitudes behave differently, such as: 

• Along the Equator, Earth's surface is moving quickest because it travels the farthest distance in 24 hours. However, the Coriolis effect is negligible along the equator. That's because objects moving in a straight line do not get deflected by the rotation of the Earth at the equator. Thus, if a wind or ocean current goes directly along the equator, it will not be deflected or curved.
• When you get closer to the poles (away from the equator), the rotation speed of the Earth slows down since the surface at higher latitudes travels a lesser distance in the same duration of time. In this case, the Coriolis force is more dominant. Bodies moving in a straight line will tend to curve increasingly as they get closer to the poles.

4.0Effects of Coriolis Effect

The Coriolis effect has a significant effect on atmospheric and oceanic processes on Earth and other celestial bodies; some of them are: 

1. Coriolis Effect Wind: The Coriolis effect has a tremendous impact on wind direction. For example, trade winds move from east to west in the two hemispheres. Due to the Coriolis effect, though, they are directed differently:
2. Trade winds are directed to the right (from northeast to southwest) in the Northern Hemisphere.
3. In the South Hemisphere, they are deflected to the left (from southeast to northwest).
4. Southward currents are always counterclockwise in the Southern Hemisphere.

5. Cyclones and Storms: Cyclones, hurricanes, and typhoons are all types of large-scale storms that are affected by the Coriolis effect. The Coriolis effect makes these storms rotate in opposite directions based on the hemisphere:

In the Northern Hemisphere, cyclones rotate counterclockwise.

In the Southern Hemisphere, cyclones are clockwise.

6. Projectile Motion of Airplanes: When aeroplanes and missiles travel over the rotating surface of Earth, the path seems bent due to the Coriolis effect. North of the Equator, projectiles are deflected to the right; south of the Equator, to the left. That is because the rotation of the Earth results in the body moving faster or slower than the ground below.