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UPSC Prelims 2025GS1GeographyIsotherms and Temperature Distribution

Q47. Consider the following statements:
Statement I: In January, in the Northern Hemisphere, the isotherms bend equatorward while crossing the landmasses, and poleward while crossing the oceans.
Statement II: In January, the air over the oceans is warmer than that over the landmasses in the Northern Hemisphere.

Which one of the following is correct in respect of the above statements?

A. Both Statement I and Statement II are correct and Statement II explains Statement I✓ Correct
B. Both Statement I and Statement II are correct but Statement II does not explain Statement I
C. Statement I is correct but Statement II is not correct
D. Statement I is not correct but Statement II is correct

Detailed Solution

✓ Correct Answer: Option A
✓ Statement I is correct
In January, during the Northern Hemisphere winter, landmasses cool down much faster and to a greater extent than oceans. This causes isotherms (lines of equal temperature) to bend equatorward (southward) over continents, indicating colder temperatures. Conversely, oceans retain heat longer, making them relatively warmer, which causes isotherms to bend poleward (northward) over oceanic areas.
✓ Statement II is correct
This differential heating and cooling capacity is precisely why the isotherms behave as described in Statement I. In winter, the air over oceans is indeed warmer than over landmasses in the Northern Hemisphere due to the high specific heat capacity of water and the influence of warm ocean currents (like the Gulf Stream and North Atlantic Drift). Therefore, Statement II correctly explains Statement I. Understanding global temperature distribution and the factors influencing isotherms is fundamental for UPSC Geography.

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