Geography Question in UPSC PRELIMS 2025 on Isotherm bending January.
Q. 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?
✅ Correct Answer: A
Explanation:
Statement I: Correct. In January, the Northern Hemisphere’s large landmasses cool down rapidly, leading to lower temperatures. Isotherms shift southward (towards the equator) over the continents. In contrast, oceans retain heat longer, so the isotherms bend northward (poleward) when passing over oceans like the North Atlantic, where warm currents like the Gulf Stream increase the surrounding air temperature.
Statement II: Statement II is correct and explains Statement I. Due to the high specific heat capacity of water, oceans cool down more slowly than land. Therefore, in winter (January), the marine areas remain warmer than the adjacent continental interiors. Because of this temperature contrast, the isotherms bend equatorward while crossing the landmasses and poleward while crossing the oceans in the month of January in the northern hemisphere.
Source: Chapter – NCERT-class 11- Fundamentals of Physical Geography
