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What Is The Coriolis Effect?
February 26, 2023 at 03:18 PM EST
By WeatherBug Meteorologist, Alyssa Robinette
It is a powerful force and affects weather patterns, ocean currents and even air travel. While it is an important phenomenon, many may have not heard about it. So, what is the Coriolis Effect?
Simply put, the Coriolis Effect makes things, like planes and currents of air, traveling long distances around the Earth appear to move at a curve as opposed to a straight line.
Different parts of the Earth move at different speeds. It takes the Earth 24 hours to rotate one time. If you are standing a foot to the right of the North or South Pole, that means that it would take 24 hours to move in a circle that is about six feet in circumference. That is about 0.00005 mph.
However, if you were to go down to the equator, it would travel at a different speed. It would still take 24 hours to rotate one time, but this time you are traveling the entire circumference of the planet, which is about 25,000 miles long. That means you would be traveling almost 1,040 mph just standing there!
Therefore, even though we are all on Earth and rotate around the Sun once per day, we are all traveling at different speeds. Our distance from the equator determines our forward speed, so the farther we are from the equator, the slower we move.
Now, let’s pretend you are standing at the equator and you want to throw a ball to your friend in the North Pole. If you throw the ball in a straight line, it will appear to land to the right of your friend because he is moving slow and has not caught up.
If we pretend that you are standing at the North Pole and you throw the ball to your friend that the equator, it will again appear to land to the right of him. But this time, it is because he is moving faster than you are and has moved ahead of the ball.
The effect of the Coriolis force is an apparent deflection of the path of an object that moves within a rotating coordinate system, but the object does not actually deviate from its path. Everywhere you play global-scale “catch” in the Northern Hemisphere, the ball will deflect to the right. Meanwhile, everywhere you play global-scale “catch in the Southern Hemisphere, the ball will deflect to the left.
The development of weather patterns, such as cyclones and trade winds, are examples of the impact of the Coriolis Effect.
Cyclones are low pressure systems that suck air into their center, or “eye.” 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 counterclockwise.
In the Southern Hemisphere, currents are deflected to the left. As a result, storm systems seem to rotate clockwise.
Outside storm systems, the impact of the Coriolis effect helps define regular wind patterns around the globe.
As warm air rises near the equator, for instance, it flows toward the poles. In the Northern Hemisphere, these warm air currents are deflected to the right as they move northward. The currents descend back toward the ground at about 30° north latitude. As the current descends, it gradually moves from the northeast to the southwest, back toward the equator. The consistently circulating patterns of these air masses are known as trade winds.
Source: NOAA, National Geographic, Britannica
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Image: How storms spin in each hemisphere because of the Coriolis Effect. (NOAA)
Simply put, the Coriolis Effect makes things, like planes and currents of air, traveling long distances around the Earth appear to move at a curve as opposed to a straight line.
Different parts of the Earth move at different speeds. It takes the Earth 24 hours to rotate one time. If you are standing a foot to the right of the North or South Pole, that means that it would take 24 hours to move in a circle that is about six feet in circumference. That is about 0.00005 mph.
However, if you were to go down to the equator, it would travel at a different speed. It would still take 24 hours to rotate one time, but this time you are traveling the entire circumference of the planet, which is about 25,000 miles long. That means you would be traveling almost 1,040 mph just standing there!
Therefore, even though we are all on Earth and rotate around the Sun once per day, we are all traveling at different speeds. Our distance from the equator determines our forward speed, so the farther we are from the equator, the slower we move.
Now, let’s pretend you are standing at the equator and you want to throw a ball to your friend in the North Pole. If you throw the ball in a straight line, it will appear to land to the right of your friend because he is moving slow and has not caught up.
If we pretend that you are standing at the North Pole and you throw the ball to your friend that the equator, it will again appear to land to the right of him. But this time, it is because he is moving faster than you are and has moved ahead of the ball.
The effect of the Coriolis force is an apparent deflection of the path of an object that moves within a rotating coordinate system, but the object does not actually deviate from its path. Everywhere you play global-scale “catch” in the Northern Hemisphere, the ball will deflect to the right. Meanwhile, everywhere you play global-scale “catch in the Southern Hemisphere, the ball will deflect to the left.
The development of weather patterns, such as cyclones and trade winds, are examples of the impact of the Coriolis Effect.
Cyclones are low pressure systems that suck air into their center, or “eye.” 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 counterclockwise.
In the Southern Hemisphere, currents are deflected to the left. As a result, storm systems seem to rotate clockwise.
Outside storm systems, the impact of the Coriolis effect helps define regular wind patterns around the globe.
As warm air rises near the equator, for instance, it flows toward the poles. In the Northern Hemisphere, these warm air currents are deflected to the right as they move northward. The currents descend back toward the ground at about 30° north latitude. As the current descends, it gradually moves from the northeast to the southwest, back toward the equator. The consistently circulating patterns of these air masses are known as trade winds.
Source: NOAA, National Geographic, Britannica
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Image: How storms spin in each hemisphere because of the Coriolis Effect. (NOAA)