UPSC Prelims 2015 · Question 5 of 98
UPSC Prelims 2015 question on Tropical Cyclones South Atlantic
- ExamUPSC CSE
- Year2015
- PaperGeneral Studies Paper I
- SubjectGeography
- TopicClimatology
- DifficultyHard
- TypeDirect
In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, cyclones does not originate. What is the reason?
Show answer
Answer: A. Sea surface temperatures are low
Verdict
The answer is that sea surface temperatures are low. Tropical cyclones do not form in the South Atlantic and south-eastern Pacific chiefly because the water there is too cool.
Analysis
Cyclogenesis requires a large sea surface warmer than about 27 degrees Celsius, the presence of the Coriolis force, small vertical wind shear, a pre existing low level disturbance and upper level divergence. In these two basins the sea surface tends to run cooler than ideal even in the southern summer, and the basin also carries climatologically high vertical wind shear. The Coriolis option is wrong because Coriolis force weakens near the equator generally, not specifically in these basins. The land option is wrong because cyclones form over ocean, not over land, so absence of land cannot be the obstacle.
Source
NCERT Fundamentals of Physical Geography, Chapter 10, page 94.
How to crack it
Learn the five formation conditions as a checklist and then ask which one is regionally absent, since a question of this type always removes exactly one. Test each option for whether it is a genuine regional peculiarity or a general property. Coriolis weakness is general to all equatorial regions, so it cannot explain a difference between basins, and that single test eliminates the strongest distractor.