Geostrophic

adjective

/ˌdʒiːəˈstrɒfɪk/

Describing atmospheric or oceanic flow in which the pressure-gradient force is balanced by the Coriolis force, resulting in wind or current flowing parallel to isobars or contours rather than across them. Geostrophic wind is an idealised approximation that holds best at mid-latitudes above the boundary layer; actual surface winds deviate from geostrophic balance due to friction. In UPSC Climatology, geostrophic balance explains why upper-level westerlies and jet streams flow roughly parallel to latitude circles rather than directly from high to low pressure.

✍️ Usage in a UPSC answer

The geostrophic approximation underpins numerical weather prediction models used by the India Meteorological Department, since upper-tropospheric flow over the subcontinent closely follows isobars during the winter westerly disturbance season.

Synonyms

isobaric flowpressure-balanced flowCoriolis-balanced flowgradient wind (approximate)

Antonyms

ageostrophic flowfrictional flowcyclostrophic flowisallobaric wind

🌱 Word Family

geostrophic (adjective), geostrophically (adverb), geostrophy (noun), ageostrophic (adjective, describing departures from balance)

🔡 Root

Greek gê = Earth + strophē = turning, twisting (from strephein = to turn); 'Earth-turning'

📜 Etymology

Formed from Greek gê (Earth) and strophe (a turning), reflecting the idea of flow that is deflected ('turned') by Earth's rotation. The term was introduced into meteorological literature in the late 19th and early 20th centuries as mathematical analysis of atmospheric dynamics developed; it is closely associated with the work of Bjerknes and his Norwegian school of meteorology in the 1910s–1920s.

🧠 Memory Hook

Geostrophic = GEO (Earth) + STROPHIC (turning). Earth's rotation turns the wind sideways so it flows ALONG isobars instead of across them. Imagine trying to roll a ball across a spinning turntable — it refuses to go straight.

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

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