Question 89 from UPSC CSE 2015 - Geography

Question

In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, cyclones do not originate. What is the reason?

IASCODEX · Accepted Answer

Correct Option: A. Sea surface temperatures are low

Strategy: Focus on the fundamental requirement for cyclone formation: warm sea surface temperatures. Compare this requirement against the conditions in the South Atlantic and South-East Pacific, noting their cooler waters. Eliminate other options as they are not the primary limiting factor in these specific regions. The correct answer is the one that directly addresses this temperature deficit.

Key Info: Tropical cyclones require sea surface temperatures of at least **27°C** to provide the necessary moisture and energy. The South Atlantic and South-Eastern Pacific regions are influenced by cold ocean currents, such as the Benguela and Humboldt Currents, which keep water temperatures below this critical threshold for most of the year.

While other factors like high vertical wind shear can inhibit cyclones, they are supplementary. The Coriolis force is adequate at these latitudes, and the absence of land is not a prohibitive factor. The seasonal presence of the Inter-tropical Convergence Zone (ITCZ) does not overcome the fundamental barrier of cool water.

Consequently, the rarity of tropical cyclones in these basins is primarily due to insufficient ocean temperatures to sustain their development. Occasional exceptions, like Hurricane Catarina in 2004, are extremely rare and typically linked to anomalous temperature spikes.

IASCODEX · Answer

Option B: Inter-tropical Convergence Zone seldom occurs

IASCODEX · Answer

Option C: Coriolis force is too weak

IASCODEX · Answer

Option D: Absence of land in those regions