Coriolis effect is what defines the deflection pattern taken by objects not firmly connected to the Earth as they travel long distances around the Earth. Large scale weather patterns are formed due to the Coriolis effect. It is named after the French mathematician Gaspard Gustave de Coriolis (1792-1843).

What causes the Coriolis Effect?

If the Earth did not rotate and remained stationary, the air would circulate between the poles and the equator in a simple back and forth manner. But, due to the rotation of air, the circulating air is deflected. Instead of following a straight pattern, the circulating air is deflected towards the right in the northern hemisphere and towards the left in the Southern Hemisphere resulting in curved paths. We call this deflection the Coriolis effect. Hence, we can conclude that the key to the Coriolis effect lies in the rotational motion of the Earth.

Different paths of Earth move at different speeds

Because Earth is a sphere, it is widest at the equator and narrower towards its top and bottom. From this, we can concur that the Earth’s circumference is greatest at the equator and lesser at higher latitudes and non-existent at the poles. Understanding this is very crucial to figure out the exciting Coriolis effect.

Mathematically Breaking it down

So now we know that the Earth rotates the fastest at the equator, slowest, nearly, zero rotation, at the top and bottom, and medium rotation speed at the top and the bottom. The circumference of the Earth at the equator is about 40,000 kilometres, and of course, we know that the time it takes to complete one rotation is 24 hours. Because speed equals distance divided by time, an object situated at the equator will move at a rate of 1,667 kilometres per hour. At a latitude of about 40 degrees North, the circumference of the Earth is about 30,600 kilometres. When divided by 24 hours,  a rotational speed of 1,275 kilometres per hour is obtained. At the North Pole and the South Pole, the distance around the Earth is zero, and zero divided by 24 hours results in a speed of zero.

How does the Coriolis Effect affect weather?

Coriolis effect highly influences weather patterns such as trade winds and cyclones. Fluids from high-pressure systems pass low-pressure systems to their right, in the Northern Hemisphere. As air masses are pulled into cyclones from all directions, they are deflected, and the storm system, a hurricane, seems to rotate counter-clockwise.

Fast-moving objects that are affected by the weather such as aeroplanes and rockets are also impacted by the Coriolis force. This is because the direction of the wind is largely affected by the Coriolis effect, hence a pilot must take this into account while charting routes for long-distance travel.