BharatNotes Geostrophic
adjectiveUsage 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
Antonyms
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.
How This Word Works in UPSC Writing
Describing flow in which the pressure-gradient force is balanced by the Coriolis force, so the air or water moves parallel to the isobars rather than across them. It is the key to reading pressure charts in GS1, because it explains why winds circulate around pressure systems instead of blowing straight from high to low. The balance holds best away from the surface, where friction is weak, and away from the equator, where the Coriolis effect vanishes.
Don’t Confuse It With
Geostrophic flow balances pressure gradient against Coriolis and runs parallel to isobars. Gradient wind additionally accounts for curvature of the flow. Surface wind is deflected across isobars because friction disturbs the balance. Cyclostrophic flow is dominated by centrifugal effects at very small scales, as in a tornado.
Hindi Meaning
भूविक्षेपी (bhūvikshepī), as in भूविक्षेपी पवन for geostrophic wind.
Common Questions
- What is geostrophic wind?
- Wind in which the pressure-gradient force is balanced by the Coriolis force, so the air flows parallel to the isobars.
- Why does geostrophic balance fail near the equator?
- Because the Coriolis effect approaches zero there, leaving nothing to balance the pressure-gradient force.
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