UPSC Prelims 2005 Q87: Geography – Atmosphere & Climatology
Assertion (A): Wind patterns are clockwise in the northern hemisphere and anti - clockwise in
the southern hemisphere.
Reason (R): The directions of wind patterns in the northern and the southern hemisphere are
governed by the Coriolis Effect.
- (a) Both A and R are individually true and R is the correct explanation of A
- (b) Both A and R are individually true but R is not the correct explanation of A
- (c) A is true but R is false
- (d) A is false but R is true
Answer: (a) Both A and R are individually true and R is the correct explanation of A
Explanation
Wind circulation and the Coriolis effect
| Part | Verdict |
|---|---|
| A. Winds clockwise in the north and anti-clockwise in the south | Accepted as true for the deflection pattern of winds around high pressure |
| R. Directions are governed by the Coriolis effect | True — deflection to the right in the north and to the left in the south |
Both are true, and R explains A: the Coriolis force deflects winds to the right in the northern hemisphere and to the left in the southern hemisphere.
Answer: (a) Both A and R are true and R explains A.
Why each option is right or wrong
- (a) CORRECT. A is true and R explains it through the Coriolis force.
- (b) Incorrect. R does explain A, so this is not the right code.
- (c) Incorrect. R is true, as the Coriolis effect governs it.
- (d) Incorrect. A is accepted as true.
Key point
Coriolis: right in the north, left in the south; zero at the equator.
Remember
The Coriolis force sets the sense of wind rotation.
Common mistakes
- Forgetting that cyclones rotate opposite to anticyclones.
- Ignoring the role of Earth's rotation.
- Thinking the Coriolis force acts at the equator.
Exam tip
Ferrel's law: deflection right in NH, left in SH.
Sources
- NCERT Class XI Geography — Atmospheric Circulation
- Savindra Singh — Climatology (Prayag Pustak Bhawan)