What is sea surface temperature rise? How does it affect the formation of tropical cyclones?
Approach · directive: “what / how”
What it asks · Define the warming of the ocean's upper layer and explain the physical link between warmer seas and the genesis, intensity and frequency of tropical cyclones.
The question has 2 parts — answer each
- Define sea surface temperature rise and what drives it
- Explain how SST rise affects the formation of tropical cyclones: energy supply, intensity, frequency and location, and the other conditions still required
Open with · Tropical cyclones are heat engines fuelled by warm ocean water — sea surface temperature of roughly 26–27°C and above is a classic precondition for their formation.
Cover
- Meaning: sea surface temperature (SST) is the temperature of the ocean's top layer; its rise reflects greenhouse warming, marine heatwaves and ENSO/IOD phases.
- Energy supply: warmer water raises evaporation; latent heat released in rising air strengthens convection and deepens the low-pressure centre.
- Intensity: high SST with deep ocean heat content allows rapid intensification — Ockhi (2017) and Tauktae (2021) jumped categories quickly.
- Frequency and location: a warmer Arabian Sea now supports more and longer-lived cyclones; seasons may lengthen.
- Other conditions still needed: Coriolis force away from the equator, low vertical wind shear, a pre-existing disturbance and upper-level divergence.
- Impacts: heavier rainfall, stronger winds and higher storm surge, made worse by sea-level rise along low coasts.
Close with · Warmer seas are loading cyclones with more energy; forecasting, coastal zoning, shelters and mangrove buffers must keep pace.
Add value (verified)
- Ministry of Earth Sciences told Parliament (2021) that cyclonic storm formation shows a decreasing trend over the Bay of Bengal but an increasing trend over the Arabian Sea. Study on Cyclones — PIB, Ministry of Earth Sciences, 15 March 2021 ↗“Studies show a decreasing trend in the frequency of formation of Cyclonic Storms over the Bay of Bengal and an increasing trend over the Arabian Sea”
Question: UPSC's CS (Main) 2024, GS Paper I — paper ↗. Approach: Minimalist IAS, checked 30 Sept 2026 (how we verify) — UPSC publishes no model answers. ·
Model answer · 228 words (UPSC limit 150) · Minimalist IAS
Tropical cyclones are heat engines fuelled by warm ocean water; a sea surface temperature of about 26–27°C through a deep layer is a precondition for their formation.
What SST rise means
- Sea surface temperature is the temperature of the ocean's top layer.
- Its rise reflects greenhouse warming, marine heatwaves and warm phases of ENSO and the Indian Ocean Dipole, and it deepens the ocean's heat content.
How it affects cyclone formation
- More fuel: warmer water raises evaporation; latent heat released as vapour condenses in rising air deepens the low-pressure core and drives the vortex.
- Wider window: the threshold is met over larger areas and for longer, extending the season and zone of genesis.
- Intensity: deep warm layers stop storms from stirring up cold water, allowing rapid intensification — Ockhi (2017), Amphan (2020) and Tauktae (2021) jumped categories within a day.
- Location: a warming Arabian Sea breeds more and longer-lived cyclones (Biparjoy, 2023); in 2021 the Ministry of Earth Sciences reported a rising trend there and a falling one over the Bay of Bengal.
- Not sufficient alone: genesis still needs Coriolis force, low vertical wind shear, a pre-existing disturbance and upper-level divergence, so frequency responds unevenly across basins.
- Impacts: heavier rain, stronger winds and higher storm surge, compounded by sea-level rise.
Warmer seas are loading cyclones with more energy; forecasting, coastal zoning, shelters and mangrove buffers must keep pace.
Written by Minimalist IAS from facts checked at source (how we verify) — a little fuller than exam length, so every part of the question is covered; in the hall, keep the structure and trim the detail. UPSC publishes no model answers: compare your structure and coverage with this, then write your own.