The following six (6) items consist of two statements, Statement I and Statement II. Examine these two statements carefully and select the correct answer using the code given below.
Statement I :
Geostrophic wind blows above a height of 600 metres, parallel to the isobars.
Statement II :
Geostrophic wind is the horizontal wind velocity, in which the Coriolis force balances the horizontal pressure force.
Both the statements are individually true and Statement II is the correct explanation of Statement I
Both the statements are individually true but Statement II is not the correct explanation of Statement I
Statement I is true but Statement II is false
Statement I is false but Statement II is true
Answer is Right!
Answer is Wrong!
This question was previously asked in
UPSC NDA-2 – 2018
Statement I is true: The geostrophic wind is a theoretical horizontal wind that flows parallel to the isobars. It is typically a good approximation of the wind speed and direction in the atmosphere above the friction layer (usually considered to be above 600-1000 meters), where the effects of surface friction are negligible. Statement II is true: The geostrophic wind occurs when the pressure gradient force (air moves from high to low pressure) is exactly balanced by the Coriolis force (deflection due to Earth’s rotation). This balance is the fundamental definition of geostrophic flow. Statement II provides the physical principle that explains why the geostrophic wind (as described in Statement I) blows parallel to the isobars above the friction layer.
– Pressure Gradient Force (PGF) drives air from high pressure to low pressure.
– Coriolis Force (CF) acts perpendicular to the wind direction, to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
– In geostrophic balance, PGF and CF are equal in magnitude and opposite in direction (acting on the wind vector).
– Friction is negligible above the boundary layer, allowing geostrophic balance to be achieved.