What is the Coriolis Effect?

The Coriolis effect is the apparent curvature of ocean currents, winds, and anything else that moves along or on the Earth's surface. It is caused by the Earth's rotation. Although an extremely important concept in physics and geography, it is often misunderstood.

A manifestation of this is that, people believe it to be responsible for the water in a drain, swirling in a particular direction in the northern hemisphere, and in a different direction in the southern hemisphere. This is not true, because the effect has nothing to do with water swirling in the drain, that is solely down to the shape of the drain.

This phenomenon is best explained as the tendency of any moving object, on or above the Earth's surface, to stray sideways from its normal course, due to the Earth's rotation. The deflection is towards the left in the southern hemisphere, while in the northern hemisphere, it is towards the right of the usual motion.

Gaspard Coriolis, a French engineer, discovered this phenomenon and also came up with mathematical formulas to explain it.

The Earth's surface does not rotate at all, at the poles, while the rotation speed is maximum along the equator. This is the reason why objects moving further from the equator drift eastwards, while the ones moving closer to the equator tend to drift westwards.

All movements on or above the Earth's surface, like winds, water flow, even artillery fired in the air, and ocean currents, are subject to this phenomenon.

The Earth's rotation is known to be the main cause of the Coriolis effect. The Earth spins in an anticlockwise direction on its axis, and because of this, objects moving on or above the surface over a long distance, are deflected, as they are moving in the opposite direction, and that too at a faster speed.

The Earth's rotation speed decreases with latitude, while this effect increases. When a plane flies above the equator, it would continue moving without any major deflection. However, if the plane flies even a little away from the equator, the plane is sure to drift, and the drift is maximum at the poles.

Hurricanes are never formed along the equator, as there is not much of an Coriolis effect there. Storms formed north of the equator develop into hurricanes, as they start rotating and gaining strength.

Apart from the distance from the equator and the Earth's rotation, speed of the moving object also determines the extent of this phenomenon. Faster the object, more the deflection. Also, on which side of the equator the object is present, determines the direction of its drift.

The most crucial impact of the Coriolis effect is on the ocean currents and wind directions. Apart from this, planes, artillery, and missiles, are certain man-made objects which are affected by this phenomenon. Its impact on wind patterns is very prominent.

When air rises up from the Earth's surface, its speed is greater than otherwise. This is because the air now does not have to move across the various landforms on the surface and as a result, its drag reduces. As faster moving objects have a greater Coriolis effect, the rising air is deflected, forming winds.

As the wind traveling across the ocean water helps in formation of ocean currents, the effect also has a bearing on the movement of ocean currents. Huge ocean currents circulate around high pressure and warm areas, formed mainly due to the deflection caused by this phenomenon. Deflecting bullets, missiles, and planes, are also a result of the same.

For instance, assume that a flight is traveling from Los Angeles to New York. If there was no rotation of the Earth, there would be no Coriolis effect and plane could travel straight to the east, but because of it, the plane movement needs to be constantly monitored so that it is in sync with the Earth's movement below. If it is left to fly straight, the plane would reach somewhere south.

Coriolis effect is therefore an indispensable tool when it comes to understanding many important concepts of physical geography.