UPSC Prelims 2002 Q149: Geography – Atmosphere & Climatology
Assertion (A): The surface winds spiral inwards upon the centre of the cyclone.
Reason (R): Air descends in the centre of the cyclone.
- (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 a correct explanation of A
- (c) A is true but R is false
- (d) A is false but R is true
Answer: (c) A is true but R is false
Explanation
Assertion-Reason: surface winds in a cyclone
| Statement | Verdict |
|---|---|
| Assertion: the surface winds spiral inwards upon the centre of the cyclone | True — winds converge towards the low-pressure centre |
| Reason: air descends in the centre of the cyclone | False — air rises at the centre of a cyclone (it descends in an anticyclone) |
| Mechanism | Converging surface air ascends at the centre, giving cloud and rain |
| Result | A is true but R is false |
In a cyclone the surface winds blow inwards and spiral towards the low-pressure centre, where the air rises. The reason, which says air descends in the centre, is wrong, so A is true and R is false. The stored key (b) is wrong.
Answer: (c) A is true but R is false.
Why each option is right or wrong
- (a) Incorrect. R is false, so it cannot explain A.
- (b) Incorrect. The stored key is wrong; R is false, not true.
- (c) CORRECT. A is true; R is false because air rises at the centre.
- (d) Incorrect. A is true; winds spiral inwards.
Key point
Cyclone: low pressure, converging and ascending air (anticlockwise in the north); anticyclone: diverging and descending air.
Remember
Cyclone: air converges and rises; anticyclone: air descends.
Common mistakes
- Trusting the stored key and treating R as true.
- Confusing cyclones with anticyclones.
- Forgetting the descent only in the calm eye of a tropical cyclone.
Exam tip
Inflow at the surface must go up, so air rises at the centre.
Sources
- NCERT Class XI — Fundamentals of Physical Geography (Cyclones)
- Savindra Singh — Climatology