Which of the following statements regarding cyclones and anti-cyclones is/are correct? 1. In the Northern Hemisphere, cyclones rotate counter clockwise and anticyclones rotate clockwise. 2. Cyclones are often associated with cloudy or rainy weather, whereas anticyclones are often associated with fair weather. 3. In the Southern Hemisphere, the cyclonic spiral will be clockwise because the Coriolis force acts to the left. Select the answer using the code given below:
- (a)1 only
- (b)1 and 2 only
- (c)2 and 3 only
- (d)1, 2 and 3
Correct — D, all three statements. In the Northern Hemisphere the Coriolis force deflects moving air to its right; air spiralling inward toward a low-pressure cyclone therefore turns counter-clockwise, while air spiralling outward from a high-pressure anticyclone turns clockwise, so statement 1 is true. A cyclone is a low-pressure system with converging, rising air that cools, condenses and produces cloud and rain, whereas an anticyclone is a high-pressure system with descending, warming air that suppresses cloud and brings settled, fair weather, so statement 2 is true. In the Southern Hemisphere the Coriolis force acts to the left, which reverses the sense of rotation and makes the cyclonic spiral clockwise, so statement 3 is true. With every statement correct, the answer is (d).
- (a)1 only — Statements 2 and 3 are also correct — cyclones do bring rainy weather while anticyclones bring fair weather, and Southern-Hemisphere cyclones do spiral clockwise, so this understates the truth.
- (b)1 and 2 only — Leaves out the true statement 3 — in the Southern Hemisphere the leftward Coriolis deflection makes the cyclonic spiral clockwise.
- (c)2 and 3 only — Leaves out the true statement 1 — in the Northern Hemisphere cyclones really do rotate counter-clockwise and anticyclones clockwise.
A cyclone is a system of low atmospheric pressure with winds spiralling inward and upward; an anticyclone is a system of high pressure with winds spiralling outward and downward. The direction of the spiral is set by the Coriolis force, which deflects moving air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, so the rotation sense reverses between the two hemispheres.
The reasoning key is the Coriolis rule of deflection — right in the north, left in the south. Apply it to inflow around a low and outflow around a high and every rotation direction follows. The weather contrast comes from vertical motion — rising air in a cyclone makes cloud and rain, sinking air in an anticyclone clears the sky.
- The Coriolis force deflects moving air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, and is zero at the Equator.
- In the Northern Hemisphere cyclonic winds blow counter-clockwise and anticyclonic winds clockwise; both senses reverse in the Southern Hemisphere.
- Cyclones are low-pressure systems of converging, rising air giving cloud and precipitation; anticyclones are high-pressure systems of subsiding air giving clear, fair weather.
- Because the Coriolis force vanishes near the Equator, tropical cyclones do not form within roughly 5 degrees of the Equator.
Pressure sets the weather and the Coriolis deflection sets the direction of spin — all three statements hold, so the answer is (d).
- Forgetting that the rotation sense flips between hemispheres because the Coriolis force acts to the right in the north but to the left in the south.
- Confusing a cyclone (low pressure, bad weather) with an anticyclone (high pressure, fair weather).
Asked as a statement-code question testing the Coriolis-driven rotation of cyclones and anticyclones in both hemispheres and their contrasting weather.
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 true and R explains A — the Coriolis effect governs the hemispheric reversal of wind rotation direction.
Tests the same principle — the Coriolis force sets opposite senses of wind rotation in the two hemispheres — which is exactly why cyclones spin counter-clockwise in the north and clockwise in the south here.
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(b) Both A and R are true but R is not the correct explanation of A — winds spiral inward because of the pressure gradient and Coriolis deflection, not because air descends in the eye.
Deals with the inward-spiralling wind structure of a cyclone — the same low-pressure, converging circulation whose direction of spin this NDA question asks about.
- practice — not a real PYQ
In the Southern Hemisphere, the Coriolis force deflects moving air to its:
- (a)right
- (b)left
- (c)front
- (d)it causes no deflection
Answer(b) left — the leftward deflection in the Southern Hemisphere makes cyclonic winds there spiral clockwise.
- practice — not a real PYQ
Fair, settled and cloud-free weather is most typically associated with:
- (a)a cyclone
- (b)an anticyclone
- (c)a cold front
- (d)a depression
Answer(b) an anticyclone — its descending, warming air suppresses cloud formation and brings clear, fair weather.