Correct Option
The correct option is 2 only.
Explanation
Winds in the upper atmosphere (typically 2-3 km above the surface) are largely free from the frictional effect of the terrain. These winds are controlled primarily by the interaction between the Pressure Gradient Force and the Coriolis Force. When these two forces achieve a state of equilibrium, the resulting wind is termed the Geostrophic Wind.
Statement-wise Analysis
- Statement 1 is Incorrect. Geostrophic wind occurs when the Pressure Gradient Force (PGF) is balanced by the Coriolis Force. Frictional force is not part of this balance; in fact, geostrophic conditions exist only where friction is negligible.
- Statement 2 is Correct. The Pressure Gradient Force acts perpendicular to the isobars (from high to low pressure), while the Coriolis Force acts perpendicular to the wind direction. When these two forces balance each other, the resultant wind blows parallel to the isobars.
- Statement 3 is Incorrect. Geostrophic winds are a phenomenon of the free atmosphere (upper troposphere), where friction is minimal. Near the surface, friction is maximum, which slows down the wind, reduces the Coriolis effect, and causes the wind to cross isobars at an angle rather than flowing parallel to them.
Key Takeaway
Geostrophic Wind is an upper-atmosphere wind that blows parallel to straight isobars due to the exact balance between the Pressure Gradient Force and the Coriolis Force, in the absence of friction.