Coriolis Effect is the apparent deflection of motion of any object traveling over the spinning Earth. A famous example is Long Max, a giant railway cannon that kept missing its target (although hugely exaggerated below). During several minutes of elapsed time while the shell was airborne, the target had moved east of its original position at the time the shell was fired. This same type of deflection also affects air molecules in wind.

The reason Coriolis Effect occurs is because the Earth spins, at a rate of 15� of longitude per hour ("angular velocity"). However, because longitude converges at the Poles, the DISTANCE velocity is greater at lower latitudes than at higher latitudes.

Furthermore, the direction of deflection differs between latitudinal hemispheres. Going FROM their original positions, objects deflect clockwise in the northern hemisphere and counterclockwise in the southern hemisphere.

Because of Coriolis Effect, aircraft pilots do not aim their planes at the intended destination when they take off! Instead, they aim for where the destination WILL be after the elapsed flight time. Assuming the plane retains the eastward momentum of its takeoff location, the pilot must add or reduce distance and alter compass direction to compensate for the expected time flying over the moving Earth.

to Temperature

to Winds

Pressure Cell

Return

Yours is visit # to this Web page since 10MAY97.

N. C. Heywood maintains this page, last updated 20JUL99.