GS Paper I — Q4
What is sea surface temperature rise? How does it affect the formation of tropical cyclones? (Answer in 150 words)
हिंदी में प्रश्न पढ़ें
समुद्री सतह के तापमान में वृद्धि क्या है? यह उष्णकटिबंधीय चक्रवातों के निर्माण को कैसे प्रभावित करता है? (उत्तर 150 शब्दों में दीजिए)
Model answer
Drafted with AI by UPSC Answer Check against this question's marking rubric, to the 150-word length. UPSC does not publish answers for Mains — this is one way to score well, not an official key. How we build rubrics and answers.
Sea surface temperature (SST) rise refers to the warming of the ocean’s upper 1–3 metres, driven by anthropogenic global warming as oceans absorb over 90% of excess planetary heat.
Causal Mechanism on Cyclone Formation
Thermodynamic Trigger: Cyclogenesis requires SST above about 26.5°C, with the warm layer extending to roughly 50 m so that churning does not bring up cool water. Higher SST enhances moisture evaporation and latent heat flux, fueling deep convective instability that powers the system's low-pressure warm core.
Rapid Intensification: Expanded marine heat content accelerates rapid intensification (RI), prolongs cyclone lifespan, and shifts genesis tracks poleward as tropical warm pools expand.
Indian Ocean Specifics: Warming of the Arabian Sea and Bay of Bengal has favoured severe, fast-intensifying events like Cyclones Amphan, Tauktae and Michaung; cyclone frequency over the Arabian Sea rose by about 52% in 2001–2019 compared with 1982–2000 (Deshpande et al., 2021).
Feedback Dynamics: While cyclone-driven ocean upwelling traditionally cools surface waters, elevated background SST overrides this negative feedback, so a larger share of cyclones reach the most intense categories (IPCC AR6), even if the total number does not rise. Strengthened early warning systems remain vital for coastal climate resilience.
How this answer will be evaluated
Framework: GS1 Geography: Mechanism and Linkage
What earns full marks: Clear definition followed by a precise explanation of the latent heat mechanism and intensity link.
Evaluation rubric
Each sub-part is marked on its own, against the marks and word limit printed on the paper.
- The answer Explain sea surface temperature rise and how it affects tropical cyclone formation. 10 marks · 150 words
explain— definition/context → points in order → small example → short close
Must cover
- SST rise: warming of the ocean's upper layer as oceans absorb over 90% of excess heat from global warming
- Genesis condition: SST above about 26.5°C with warm water extending to roughly 50 m (ocean heat content), plus Coriolis force, low vertical wind shear and pre-existing disturbance
- Mechanism: more evaporation and latent heat release feed convection and the warm core, lowering central pressure
- Effects: rapid intensification, higher peak intensity and rainfall, longer life, poleward and seasonal shifts; Indian examples (Amphan, Tauktae, Biparjoy) and rising Arabian Sea activity
Loses marks
- Claiming SST alone forms cyclones
- Confusing SST with atmospheric temperature
Earns more
- Cold wake/upwelling as a negative feedback weakened by deeper warm layers
- IPCC AR6: higher proportion of intense cyclones, frequency change uncertain
Extra mark
- Diagram of cyclone structure and energy flow
What "Explain" is asking you to do
Make the working of something clear — what sets it off, what follows from what, and what it produces. Explain is the Commission's mechanism word: it dominates the technical papers and the “explain why” stems, where the marks sit in the causal chain and not in the label.
Structure that answers it
State what it is → the initiating condition → the chain of cause, step by step → an instance where it plays out → what the chain produces
Where marks are lost
Describing what something looks like instead of why it works that way. Naming the stages without linking them reads as description too.
Practice this exact question
Write your answer and it is marked point by point against the model answer above — what you covered, what you missed, what you got wrong.
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