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 with respect to the above statements? (UPSC Prelims 2025)

Question

The correct answer is [A] Both Statement I and Statement II are correct and Statement II explains Statement I. This question focuses on the seasonal distribution of temperature and how isotherms (lines joining places of equal temperature) behave over land and water.

Statement I (Correct): In January, which is winter in the Northern Hemisphere, isotherms show a distinct shift. As they move from the ocean to a landmass, they bend equatorward (southward). Conversely, when they move from land to the ocean, they bend poleward (northward). This happens because land cools down much faster than water.
Statement II (Correct): During winter, landmasses lose heat rapidly while oceans retain heat due to the high specific heat capacity of water. Consequently, the air over the oceans is warmer than the air over the landmasses at the same latitude. This temperature difference is the physical reason why isotherms must shift their position to maintain a constant temperature reading.

Explanation of the Link: Since the ocean is warmer in January, a specific isotherm (e.g., 10°C) will be found at a higher latitude (further north) over the water. As that same 10°C line reaches the cold landmass, it must \"dip\" south toward the equator to find a location warm enough to maintain that 10°C value. Thus, Statement II is the direct cause of the phenomenon described in Statement I.In the Southern Hemisphere during January (summer), the effect is reversed: isotherms bend poleward over land and equatorward over the oceans.

GKToday Admin · Accepted Answer

Both Statement I and Statement II are correct and Statement II explains Statement I The correct answer is [A] Both Statement I and Statement II are correct and Statement II explains Statement I. This question focuses on the seasonal distribution of temperature and how isotherms (lines joining places of equal temperature) behave over land and water.

Statement I (Correct): In January, which is winter in the Northern Hemisphere, isotherms show a distinct shift. As they move from the ocean to a landmass, they bend equatorward (southward). Conversely, when they move from land to the ocean, they bend poleward (northward). This happens because land cools down much faster than water.
Statement II (Correct): During winter, landmasses lose heat rapidly while oceans retain heat due to the high specific heat capacity of water. Consequently, the air over the oceans is warmer than the air over the landmasses at the same latitude. This temperature difference is the physical reason why isotherms must shift their position to maintain a constant temperature reading.

Explanation of the Link: Since the ocean is warmer in January, a specific isotherm (e.g., 10°C) will be found at a higher latitude (further north) over the water. As that same 10°C line reaches the cold landmass, it must \"dip\" south toward the equator to find a location warm enough to maintain that 10°C value. Thus, Statement II is the direct cause of the phenomenon described in Statement I.In the Southern Hemisphere during January (summer), the effect is reversed: isotherms bend poleward over land and equatorward over the oceans.

Current Affairs

Daily MCQs

Monthly MCQs

Topic Wise CA MCQs

CA MCQs in Other Languages

GK MCQs Section

SSC/RRB/States Level MCQs