Air

The Coriolis effect

The Coriolis effect, that gets its name from the physicist Gaspard Coriolis who postulated the theory in the 19th century, is an effect, caused by the Earth’s rotation, that acts on moving bodies on the Earth’s surface. It is also known as Coriolis force, but this definition is incorrect since it is not really a force, even though its effects may appear similar to those of a force to an observer within the system. As a consequence of the Earth’s rotation, any object that travels in a straight line will undergo a deviation in its path that will take it far from the desired point unless it can carry out continuous changes in its course. In the Northern Hemisphere, every moving object will tend to drift towards the right, while in the southern hemisphere it is towards the left. To an observer within the system, it may seem that there is a mysterious ‘force’ that pushes objects off their course, but in actual fact, it is an effect caused by ‘displacement’ of the Earth’s surface under the moving object. The Coriolis effect is proportional to the angular velocity of the Earth (that is constant), to the speed of the moving object and to the latitude: it is null at the Equator and maximum at the Poles. This effect can be observed in many daily situations: in the Northern Hemisphere aeroplanes have to change their course towards the left, the right railway track undergoes a greater wear, etc... Similarly, even winds undergo deviations: if the Earth were motionless, the winds would tend to move in a N-S direction, from the Equator to the Poles along the meridians, but as a result of the Coriolis effect, winds from the North tend to become winds from the NE and so on.