Previous Year Question
Given below are two statements, one is labelled as Assertion (A) and the other as Reason (R).
Assertion (A): Jet streams discovered during World War II are high altitude easterly winds.
Reason (R): Jet streams flow with a speed of 300–500 km/hour.
Select the correct answer from the codes given below:
Both (A) and (R) are true and (R) is the correct explanation of (A).
(A) is false, but (R) is true.
Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(A) is true, but (R) is false.
Correct Answer: B
Detailed Solution
Jet Streams are very fast and narrow air currents found in the upper atmosphere. The Earth's major Polar and Subtropical Jet Streams generally flow from west to east, and are therefore regarded as Westerly winds. The Assertion describes them as Easterly winds, making the Assertion incorrect.
Jet Streams generally occur in the upper troposphere, roughly around 8–14 km above the Earth's surface. Their position and speed vary according to season and temperature gradients.
Reason (R) is correct in the examination context. Strong Jet Streams can attain speeds of around 300–500 km/h. However, this is not their constant speed; their normal speed may be lower. Very strong winter polar jets can exceed 400 km/h.
Jet Streams also play an important role in transporting weather systems from one region to another. Changes in their position can therefore influence patterns of temperature, rainfall and storms.