Atmospheric Pressure & Planetary Winds – NDA Geography PYQs

Question 1 [NDA 2009-I]
Coriolis Force arises due to:
(a) Revolution of Earth
(b) Rotation of Earth
(c) Gravitational force of Moon
(d) Unequal heating of Earth

Answer: (b) Rotation of Earth
The Coriolis Force is a deflecting force caused by the Earth’s rotation. As the Earth spins, objects moving across its surface are deflected — to the right in the Northern Hemisphere and to the left in the Southern. This force does not arise from revolution (the annual orbit around the Sun), gravity, or temperature differences.

Question 2 [NDA 2009-II]
Which of the following statements regarding the various pressure belts are correct?

1. Equatorial low pressure belt is thermally induced.
2. Sub-tropical high pressure belt is dynamically induced.
3. Sub-polar low pressure belt is thermally induced.
4. Polar high pressure is thermally induced.

(a) 1, 2 and 3 only
(b) 1, 2 and 4 only
(c) 2, 3 and 4 only
(d) 1, 2, 3 and 4

Answer: (b) 1, 2 and 4 only
Statement 1 is correct — equatorial low is thermally induced by intense surface heating. Statement 2 is correct — subtropical high is dynamically induced by sinking air in the atmospheric circulation. Statement 3 is wrong — sub-polar low is dynamically induced by the meeting of contrasting air masses and the forced ascent of air, not by thermal heating. Statement 4 is correct — polar high is thermally induced by extreme cold and dense sinking air.

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Question 3 [NDA 2011-I]
Which of the following statements are correct regarding Southern hemisphere winds?

1. The Roaring Forties are found between 40 and 50 degrees South.
2. Westerlies blow from the South to the North.

(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

Answer: (a) 1 only
Statement 1 is correct — the Roaring Forties are the strong westerly winds that blow between 40°S and 50°S over the open Southern Ocean. Statement 2 is wrong — westerlies in the Southern Hemisphere blow from the northwest to the southeast (or broadly from west to east) — not from south to north.

Question 4 [NDA 2012-II]
Which of the following statements about jet streams is/are correct?

1. They are found in the upper troposphere.
2. Their speed varies between 110 and 184 km/h.
3. They generally move from west to east.
4. They influence the movement of cyclones.

(a) 1 only
(b) 1 and 3 only
(c) 1, 2 and 3 only
(d) 1, 2, 3 and 4

Answer: (d) 1, 2, 3 and 4
All four statements correctly describe jet streams. Jet streams are fast-moving bands in the upper troposphere. Their speeds average between 110 and 184 km/h though they can reach much higher. They generally move from west to east. The polar front jet stream influences the path of mid-latitude cyclones and therefore significantly affects weather patterns.

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Practice Question 1 (Important for NDA)
Consider the following statements about Intertropical Convergence Zone:

1. It is a region near the equator where trade winds from both hemispheres converge.
2. It migrates north and south following the position of the overhead Sun.
3. It always lies exactly on the geographical equator throughout the year.

Which of the statements given above are correct?
(a) 1 only
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1, 2 and 3

Answer: (b) 1 and 2 only
Statement 1 is correct — the ITCZ is where northeast and southeast trade winds converge near the equator. Statement 2 is correct — the ITCZ migrates north and south with the seasons following the Sun. Statement 3 is wrong — the ITCZ does NOT always lie exactly on the geographical equator. It shifts north in summer and south in winter.