Coriolis

The apparent deflection of freely moving objects (winds, ocean currents, projectiles) to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, arising from Earth's rotation rather than any actual force. The Coriolis effect, named after the French engineer Gaspard-Gustave de Coriolis, is fundamental to the formation of trade winds, westerlies, jet streams, cyclonic circulation, and the geostrophic balance governing ocean gyres. In UPSC Climatology, the Coriolis effect explains the anticlockwise rotation of Northern Hemisphere cyclones (e.g., Bay of Bengal tropical cyclones) versus clockwise rotation in the Southern Hemisphere.