| 1. What is the Coriolis Effect? |
| 2. What causes the Coriolis Effect? |
| 3. Impact of the Coriolis Effect |
The apparent deflection of objects (like winds, airplanes, missiles, and ocean currents) moving in a straight path relative to the Earth’s surface is known as the Coriolis Effect or Coriolis Force.
For example, when viewed from the ground below, a plane flying in a straight-path north will appear to take a curved path.
It was first explained by a French scientist and mathematician named Gaspard-Gustave de Coriolis in 1835. The strength of the deflection is proportional to the speed of the Earth’s rotation at different latitudes. As you move further away from the equator toward the poles, the Coriolis Effect becomes more extreme.
The Coriolis effect varies with ground speed (or wind speed) and is greatest at the Poles and zero at the Equator.
The Earth’s rotation is the main cause of the Coriolis effect. As the Earth spins in a counter-clockwise direction on its axis, anything flying or flowing over a long distance above its surface is deflected. This occurs because as something moves freely above the Earth’s surface, the Earth moves east under the object at a faster speed.
As latitude increases and the speed of the Earth’s rotation decreases, the Coriolis effect increases. A pilot flying along the equator itself would be able to continue flying along the equator without any apparent deflection. However, a little to the north or south of the equator, and the pilot would be deflected. The pilot’s plane would experience the most deflection possible as it nears the poles.
Hurricanes are also formed due to latitudinal variations in deflection. These storms don’t form within five degrees of the equator because there is not enough Coriolis rotation. As we move further north of the equator, tropical storms can begin to rotate and strengthen to form hurricanes. In addition to the speed of the Earth’s rotation and latitude, the faster the object itself is moving, the more deflection there will be.
The direction of deflection from the Coriolis effect depends on the object’s position on Earth. In the Northern Hemisphere, objects deflect to the right, while in the Southern Hemisphere they deflect to the left.
Deflection of winds
As air rises off of the Earth’s surface, its speed over the surface increases because there’s less drag as the air no longer has to move across the Earth’s many types of landforms. Because the Coriolis effect increases with an object’s increasing speed, it significantly deflects air flows.
In the Northern Hemisphere these winds spiral to the right and in the Southern Hemisphere they spiral to the left. This usually creates the westerly winds moving from the subtropical areas to the poles.
Deflection of ocean currents
The Coriolis effect also affects the movement of the ocean’s currents because currents are driven by the wind moving across the waters of the ocean. Many of the ocean's largest currents circulate around warm, high-pressure areas called gyres. The Coriolis effect creates the spiral pattern in these gyres.
Effect on man-made items like planes and missiles
The Coriolis effect has a significant impact on man-made items such as planes and missiles, especially when they travel long distances over the Earth. If the Earth did not rotate, there would be no Coriolis effect and thus the pilot could fly in a straight path to the destination direction. However, due to the Coriolis effect, the pilot has to constantly correct for the Earth's movement beneath the plane. Without this correction, the plane would land somewhere other than the intended destination.
