Question map
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 ?
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.
PROVENANCE & STUDY PATTERN
Full viewThis 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.
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?
- Statement 2: Do only some cyclones (tropical cyclones/hurricanes/typhoons) develop an eye, or do all cyclones develop an eye?
- Statement 3: Is the temperature inside the eye of a tropical cyclone approximately 10°C lower than the temperature of the surrounding eyewall and environment?
- 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.
- 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.
- 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.
- Explicitly states that not all cyclones have an eye, directly contradicting the idea that all do
- Distinguishes the eye as a feature of some cyclones (narrow interpretation) versus the cyclone centre (broader interpretation)
- Links eye development to storm intensity (cyclones with maximum sustained wind speed > 119 kmph tend to develop an eye)
- Implies eye formation is conditional on reaching sufficiently high wind speeds rather than universal
- Explains the physical mechanism (centripetal/tangential forces) that produces an eye in a strong vortex
- States eye diameter depends on wind speed, implying weaker systems may not form a distinct eye
- Explicitly states the storm has a warm-core structure, meaning the center is warmer than the surrounding environment.
- Directly contradicts the claim that the eye is colder by ~10°C; instead it says the center is warmer at a given height.
- Describes the eye as 'warm and moist' and identifies warm temperature anomalies within the eye.
- Explains the warming mechanisms (subsidence and adiabatic warming) that make the eye warmer than the eyewall/environment, not colder.
States that air in the eye is slowly sinking and heated adiabatically; the eye temperature may be 10°C warmer (at 12 km) and only 0–2°C warmer at the surface versus the surrounding environment.
A student could use the adiabatic warming principle plus typical vertical profiles to judge that the eye is generally warmer, not ~10°C colder, comparing reported eye vs eyewall temperatures at surface and aloft.
Notes the central 'eye' has the highest temperature due to descending air currents.
Combine this rule with basic thermodynamics (subsidence warms) to infer the eye should be warmer than surrounding eyewall, so a ~10°C colder eye is unlikely.
Describes the eye as an area of comparatively light winds, fair weather, and little or no precipitation — consistent with subsidence and warming.
Use the association of clear, subsiding air with warming to predict the eye's temperature relative to convective eyewall regions.
Gives eye size and notes winds are light in the eye while strongest winds occur just outside the eye (eyewall), implying contrasting dynamic and thermodynamic conditions between eye and eyewall.
A student could infer that intense eyewall convection (cooler by latent cooling) contrasts with a calmer, subsiding (warmer) eye, arguing against a much colder eye.
Explains eye formation via vortex dynamics (centripetal/tangential forces) producing a calm central region — a mechanical basis for the distinct microclimate of the eye.
Combine this dynamical explanation with knowledge that calm central regions often involve subsidence and warming to assess temperature differences between eye and eyewall.
- [THE VERDICT]: Conceptual Trap + Standard Books. Statement 1 is a 'Sitter' (basic error), but Statement 3 is a 'Trap' (reversing the warm-core logic).
- [THE CONCEPTUAL TRIGGER]: Climatology > Atmospheric Circulation > Tropical vs. Temperate Cyclones & Jet Streams.
- [THE HORIZONTAL EXPANSION]: 1. Jet Stream Types: Polar Front, Subtropical, and the temporary Tropical Easterly Jet (TEJ). 2. Cyclone Structure: Eye (calm, warm), Eyewall (max wind, rain), Spiral Bands. 3. 'Warm Core' vs 'Cold Core' distinction. 4. Eyewall Replacement Cycles (why intensity fluctuates).
- [THE STRATEGIC METACOGNITION]: When studying physical phenomena, always ask: 'Is this symmetrical?' (Does it happen in the South?) and 'What is the energy source?' (Latent heat = Warm Core). Never memorize a feature (like 'The Eye') without its boundary conditions (only in intense storms).
There are two principal jet types — polar and subtropical — occupying different latitude boundaries and influencing weather.
High-yield for questions on jet classification, latitude/location of jets, and their roles in mid-latitude vs. tropical weather; connects to monsoon dynamics and cyclone development and enables comparative questions on jet impacts.
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Upper Tropospheric Westerlies > p. 385
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Subtropical Jet Stream (STJ) > p. 387
Jet streams differ in strength and continuity between hemispheres (north generally stronger; STJ continuous in south, intermittent in north).
Important for comparative geography questions and for explaining regional climate contrasts (e.g., why Northern Hemisphere jets can be more forceful); links to temperature gradients, seasonality, and monsoon interactions.
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Upper Tropospheric Westerlies > p. 385
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Subtropical Jet Stream (STJ) > p. 387
Jet streams arise from large-scale thermal/pressure contrasts between air masses and the Coriolis effect shaping high-altitude westerly flows.
Core physical mechanism useful for mechanistic explanations in answers about wind systems, Rossby waves, and atmospheric circulation; equips aspirants to tackle cause-effect and process-based questions.
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Upper Tropospheric Westerlies > p. 385
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > 27. Jet streams > p. 384
The presence and size of a cyclone's eye are controlled by wind speed and vortex dynamics, so only sufficiently intense storms develop a clear eye.
High-yield for UPSC geography and disaster management: explains why only stronger tropical cyclones produce an eye, links cyclone structure to intensity classification and impacts at landfall. Helps answer questions on cyclone anatomy, severity indicators, and warning criteria.
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 26: Tropical Cyclones > Eye Formation > p. 364
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 26: Tropical Cyclones > Stage 4: Tropical Cyclone (Maximum Sustained Wind Speed > 119 Kmph) > p. 363
The eye is the central low-pressure region with calm, light or variable winds and reduced cloudiness compared to the eyewall.
Fundamental fact frequently tested in objective and descriptive questions; helps differentiate tropical from temperate cyclones, and is essential for understanding storm surge, eyewall hazards, and forecasting implications.
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 8: Natural Hazards and Disaster Management > Te following conditions are required for the origin and development of a tropical cyclone: > p. 49
- Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 4: Climate of India > TROPICAL CYCLONES > p. 27
- Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 6: Pressure, Winds, Storms, and Cyclones > 6.6 Cyclone > p. 92
Cyclone intensity thresholds (e.g., sustained winds ≈119 kmph) mark transitions in structure, including the tendency to develop an eye.
Useful for MCQs and mains answers linking meteorological thresholds to hazard severity, preparedness measures, and classification terms (tropical storm vs cyclone/hurricane). Enables reasoning about which systems warrant higher warnings and why.
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 26: Tropical Cyclones > Stage 4: Tropical Cyclone (Maximum Sustained Wind Speed > 119 Kmph) > p. 363
Descending air in the cyclone eye warms by adiabatic compression, raising temperatures in the eye center.
High-yield for explaining why the eye can be warmer than its surroundings; connects atmospheric thermodynamics (adiabatic processes, lapse rate) with cyclone structure. Mastery helps answer questions on temperature profiles, stability, and vertical motion in cyclones.
- Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 26: Tropical Cyclones > Characteristics of The Eye > p. 366
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 8: Natural Hazards and Disaster Management > Te following conditions are required for the origin and development of a tropical cyclone: > p. 49
The Tropical Easterly Jet (TEJ). While standard jets exist in both hemispheres, the TEJ is a seasonal, Northern Hemisphere-specific phenomenon linked to the Tibetan Plateau heating. UPSC will likely ask about this 'exception' to the symmetry rule next.
Apply the 'Engine Logic'. Tropical cyclones are heat engines driven by latent heat release. Heat = Energy. If the core were 10°C *colder* (Statement 3), the low pressure would collapse, and the engine would die. The core *must* be warmer to sustain the system. Also, Statement 1 ('Only Northern Hemisphere') violates the basic symmetry of a rotating sphere (Earth); physics applies to the South too.
GS-3 Disaster Management: The 'Eye' is a deceptive killer. The calm center often lures people out of shelters before the rear eyewall hits (the 'second attack'). Understanding this structure is critical for designing public warning protocols (e.g., 'Wait for the all-clear signal').