Coriolis

noun (used attributively); proper noun (eponym)

/ˌkɒrɪˈəʊlɪs/

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, formally described by French engineer Gaspard-Gustave de Coriolis in 1835, 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.

✍️ Usage in a UPSC answer

The Coriolis effect deflects the southwest monsoon winds northeastward as they cross the equator, converting the southerly flow into the moisture-laden southwesterlies that drive India's June–September rainfall season.

Synonyms

Coriolis forceCoriolis deflectionrotational deflectioninertial deflection

Antonyms

geostrophic balance (counteracting force concept)pressure-gradient force (opposing driver)

🌱 Word Family

Coriolis effect (compound noun), Coriolis force (compound noun), Coriolis parameter (technical noun)

🔡 Root

Proper noun: from Gaspard-Gustave de Coriolis (1792–1843), French mathematician and engineer

📜 Etymology

Named after Gaspard-Gustave de Coriolis, who published his mathematical treatment of rotating reference frames in 1835 in Mémoire sur les équations du mouvement relatif des systèmes de corps. The term Coriolis force or Coriolis effect entered meteorological and oceanographic literature in the late 19th century as scientists applied his mechanics to atmospheric circulation. It is a fictitious (inertial) force — real only in a rotating frame of reference.

🧠 Memory Hook

Coriolis = CORE-of-Earth's rotation. In the Northern Hemisphere, winds veer RIGHT — remember 'Northern = Right-hand rule'. Imagine throwing a ball northward on a spinning merry-go-round: it curves to the right.

📝 Seen in UPSC Question Papers

Prelims 2024 — Physical Geography

Real UPSC previous-year questions whose text uses “Coriolis” — proof this word earns its place on your list.

🌍 Geography 📖 Seen in: Plate Tectonics & Volcanism — Continen...

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