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Q9 (IAS/2020) Geography › World Physical Geography › Atmospheric pressure winds Official Key

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 10℃ lesser than that of the surroundings. Which of the statements given above is/are correct ?

Result
Your answer: —  ·  Correct: C
Explanation

The correct answer is Option 3 based on the following analysis of the statements:

  • Statement 1 is incorrect: Jet streams are high-altitude westerly winds that occur in both the Northern and Southern Hemispheres. They are driven by atmospheric heating and the Coriolis effect, which are global phenomena.
  • Statement 2 is correct: The "eye" is a characteristic feature of mature tropical cyclones (typhoons or hurricanes). Extra-tropical cyclones and weaker tropical disturbances do not develop this distinct central feature. Therefore, only some specific, intense cyclones possess an eye.
  • Statement 3 is incorrect: The eye of a cyclone is a zone of subsiding air, which warms adiabatically. Consequently, the temperature inside the eye is actually higher (often 10°C or more) than the surrounding environment, not lesser. It is a warm-core phenomenon.

Since only Statement 2 is scientifically accurate, Option 3 is the right choice.

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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. Consider the following statements : 1. Jet streams occur in the Northern Hemisphere only. 2. Only some cyclones develop an eye. 3. The te…
At a glance
Origin: Books + Current Affairs Fairness: Moderate fairness Books / CA: 6.7/10 · 3.3/10
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This is a 'Concept Clarity' check disguised as a factual question. It punishes surface-level reading (knowing cyclones have eyes) while rewarding depth (knowing *which* cyclones have eyes and the thermodynamic 'warm core' structure). It is 90% solvable via standard Physical Geography texts (NCERT/GC Leong/PMF IAS) without needing niche current affairs.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Do atmospheric jet streams occur only in the Northern Hemisphere, or do jet streams exist in both the Northern and Southern Hemispheres?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Upper Tropospheric Westerlies > p. 385
Presence: 5/5
“• Jet streams are produced due to winds flowing from the tropics towards poles in the upper troposphere (just below the tropopause). Both the Northern and Southern hemispheres have jet streams, although the jet streams in the north are more forceful due to greater temperature gradients.• The jet stream produced between polar and temperate air masses is called the polar jet stream or polar jet. The jet stream produced between temperate and tropical air masses is called the subtropical jet stream. In the polar jet streams wind flows from the temperate region towards the polar region, and in the subtropical jet streams, winds flow from subtropics towards the temperate region.• In the upper troposphere, the wind flows from less dense air mass towards the poles due to thermal effect (poles receive less heat and equator receives more heat.”
Why this source?
  • Explicitly states both the Northern and Southern hemispheres have jet streams.
  • Explains jet-stream origin as upper-tropospheric winds from tropics toward poles, a global process applicable in both hemispheres.
  • Notes hemispheric difference in strength (north stronger due to larger temperature gradients), implying presence in both.
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Subtropical Jet Stream (STJ) > p. 387
Presence: 5/5
“• During winter, the STJ is nearly continuous in both hemispheres. It exists all year in the southern hemisphere. However, it is intermittent in the northern hemisphere during summer when it migrates north.• The STJ can be temporarily displaced when strong mid-latitude troughs (remnants of temperate cyclones) extend into subtropical latitudes. When these displacements occur, the subtropical jet can merge with the polar front jet (related to cloudbursts. We will study this in the chapter on Indian Monsoons).• STJ is closely connected to the Indian and African summer monsoons (we will study this in the chapter on Indian Monsoons).”
Why this source?
  • Describes the subtropical jet (STJ) as nearly continuous in both hemispheres during winter.
  • Specifies the STJ exists year-round in the Southern Hemisphere but is intermittent in the Northern Hemisphere, directly comparing both hemispheres.
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > 27. Jet streams > p. 383
Presence: 4/5
“Jet streams are • circumpolar (circle around the earth with poles as their centres),• narrow, concentrated bands of (the air in the stream is directed towards the axis of the stream making it very narrow ― 50-150 km across),• upper tropospheric,• westerly,• geostrophic streams,• flowing at high velocity,”
Why this source?
  • Defines jet streams as circumpolar bands that circle the Earth with the poles as centres, implying jets around both poles.
  • Characterises jet streams as upper-tropospheric westerly flows, a global attribute consistent for both hemispheres.
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