Consider the following statements :

Statement I : In January, in the NorthernHemisphere, 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 NorthernHemisphere.

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
(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

The correct answer is (a) Both Statement I and Statement II are correct and Statement II explains Statement I.

Explanation

Analyze Statement II (The Cause): “In January, the air over the oceans is warmer than that over the landmasses in the Northern Hemisphere.”
- This statement is correct. January is winter in the Northern Hemisphere. Land has a low specific heat capacity, meaning it heats up and cools down very quickly. Water (oceans) has a high specific heat capacity, so it cools down much more slowly.
- Therefore, in winter, the landmasses become significantly colder than the oceans at the same latitude.
Analyze Statement I (The Effect): “In January, in the Northern Hemisphere, the isotherms bend equatorward while crossing the landmasses, and poleward while crossing the oceans.”
- This statement is correct. An isotherm is a line connecting points of equal temperature.
- Over land: Because the land is very cold (as per Statement II), the isotherm must bend equatorward (south) to find the same temperature.
- Over oceans: Because the ocean is relatively warm (as per Statement II), the isotherm bends poleward (north) to find the same temperature.
Analyze the Relationship:
- Statement II provides the precise physical reason (differential heating/cooling of land and water) for the behavior of the isotherms described in Statement I. The fact that oceans are warmer than land in winter causes the isotherms to bend.
- Therefore, both statements are correct, and Statement II is the correct explanation for Statement I.