Previous Year Question
Consider the following statements.
Jet streams occur in the Northern Hemisphere only.
Only some cyclones develop an eye.
The temperature inside the eye of a cyclone is nearly 10°C lesser than that of the surroundings.
Which of the statements given above is/are correct?
Correct Answer: C
Detailed Solution
Statement 1 is incorrect: Jet streams occur in both the Northern and Southern Hemispheres, not only in the Northern Hemisphere.
They are narrow bands of very strong winds flowing close to the tropopause.
Major jet streams in both hemispheres include the subtropical westerly jet and the polar-front jet.
Because of Earth’s rotation and horizontal temperature gradients, their predominant movement is from west to east.
Their position, velocity and course change with the seasons.
Statement 2 is correct: A clearly defined eye develops only in some well-organised cyclones.
The eye is principally associated with powerful and well-organised tropical cyclones.
Weak tropical disturbances, depressions and generally extra-tropical cyclones do not possess a distinct eye.
The eye is a roughly circular central region with comparatively calm conditions and little precipitation.
It is surrounded by the eyewall, which contains the cyclone’s strongest winds and heaviest rainfall.
Statement 3 is incorrect: A tropical cyclone is a warm-core system.
Air inside the eye descends and becomes warmer through adiabatic compression.
At the same altitude, the eye is therefore warmer than the surrounding eyewall, not approximately 10°C colder.
Surface winds may be relatively weak inside the eye, while the surrounding eyewall contains the cyclone’s maximum wind speeds.