Corioliseffect

The Corioliseffect is an apparent deflection of moving objects observed in a rotating reference frame, most prominently on the Earth’s surface. It arises from the conservation of angular momentum as objects move across a rotating platform, causing trajectories to appear curved relative to the surface. The effect is most noticeable for large-scale motions such as atmospheric and oceanic currents and for long-range projectiles. The term is sometimes written as Corioliseffect.

In a frame that rotates with angular velocity vector Ω, the equations of motion include the Coriolis force F_cor = -2m Ω × v', where m is mass and v' is velocity in the rotating frame. A convenient form introduces the Coriolis parameter f = 2Ω sin φ, with φ the latitude, giving the acceleration due to the Coriolis effect as a_cor = -f k × v', where k is the local vertical unit vector. The magnitude of the deflection therefore increases with both speed and latitude, and the direction is perpendicular to the velocity.

On Earth, this deflection causes moving objects to bend to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. It shapes large-scale weather patterns, wind and current directions, cyclones and anticyclones, jet streams, and ocean gyres, while also affecting artillery, aviation, and spacecraft re-entry planning. The Coriolis effect is negligible for short-range motions or experiments at small scales but essential for accurate modeling of geophysical and engineering systems.

The effect is named after Gustave-Gaspard de Coriolis, who described it in 1835. It remains a foundational concept in meteorology, oceanography, and geophysical fluid dynamics.