Penn StateNASA

The Coriolis Effect


The Coriolis Effect arises because our planet is spinning, which means that objects near the equator are moving at much faster velocities than objects at higher latitudes. If you were standing on the equator, you would be traveling at about 1600 km/hr; if you were standing at the North Pole, you would be traveling at 0 km/hr. This means that a parcel of air moving across the surface moves into regions where the whole planet is traveling either slower or faster. The physics of this phenomenon are well-understood, and without getting into the mathematics behind it, we can summarize it with 4 simple statements:

  1. objects moving in the northern hemisphere get deflected to the right as you look in the direction of motion;
  2. objects moving in the southern hemisphere get deflected to the left as you look in the direction of motion;
  3. the strength of this effect, this deflection, is greater as you approach the poles; and
  4. the strength of the effect is more important at higher velocities (e.g., a glacier does not respond to Coriolis).

Let’s think for a minute about what this general circulation of the atmosphere does. Among other things, it mixes the atmosphere quite thoroughly, and this means that the concentrations of things like greenhouse gases get homogenized. It also means that heat gets transferred. Polar air finds its way toward lower latitudes, where it cools the surface and in so doing warms itself, and warmer air finds its way higher latitudes, where it gives up its heat to the surroundings and thus cools.

But this general circulation does more — it drives the circulation of the surface waters in the ocean.