Q. Consider the following statements:
1. Jet streams occur in the Northern Hemisphere only.
2. Only some cyclones develop an eye.
3. The temperature inside the eye of a cyclone is nearly 10ºC lesser than that of the surroundings.
Which of the statements given above is/are correct?
a) 1 only
b) 2 and 3 only
c) 2 only
d) 1 and 3 only
Correct Answer : b) 2 only
Question from UPSC Prelims 2020 GS Paper
Explanation:
1. Jet streams occur in both the Northern Hemisphere and the Southern Hemisphere.
Jet streams are fast flowing, narrow air currents found in the atmospheres of some planets, including Earth. On Earth, the main jet streams are located near the altitude of the tropopause and are westerly winds (flowing west to east). They occur in both the Northern Hemisphere and the Southern Hemisphere. Therefore, the assertion that jet streams occur only in the Northern Hemisphere is false.
2. Only some cyclones develop an eye.
The eye of a cyclone is a region at the center of a cyclone in which the weather is calm and the sky is clear or only partially covered by clouds. Not all cyclones develop a well-defined eye; it is characteristic of strong tropical cyclones (notably, hurricanes and typhoons). The formation of an eye is associated with the maturity of the cyclone, and weaker cyclones may not develop an eye at all.
3. The temperature inside the eye of a cyclone is nearly 10ºC lesser than that of the surroundings.
This statement is incorrect. In fact, the temperature inside the eye of a cyclone is warmer than its surroundings. The eye is warmer partly because of the sinking air within it, which compresses and warms up. The temperature difference can contribute to the cyclone’s intensity. The exact temperature difference can vary, but the key point is that the eye is warmer, not cooler, than its surroundings.
