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
- 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
Correct answer
Explanation
The correct answer is A, both statements are correct and Statement II explains Statement I. In the northern winter the oceans stay warmer than the land, and that temperature contrast is what bends the isotherms.
Isotherms are lines joining places of equal temperature. Land heats and cools quickly, while water has a high specific heat and holds its warmth. In January it is winter in the Northern Hemisphere, so the continents become very cold and the oceans remain relatively warm. A given temperature is therefore found farther south over land, so the isotherm dips towards the equator, and farther north over the sea, so it bends towards the pole. The North Atlantic Drift makes the poleward bend over the North Atlantic especially sharp. In July the pattern reverses.
B is wrong because Statement II does explain Statement I.
C is wrong because Statement II is correct.
D is wrong because Statement I is correct.
Exam tip: January in the north: isotherms bend equatorward over land and poleward over the warmer ocean; in July the bends reverse.
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