UPSC Prelims 2015 Question:

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

Explanation:

• Cyclones are low-pressure systems that are powered by warm ocean waters.
  
  
• In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, sea surface temperatures are slightly lower than those required for tropical cyclone formation. Vertical wind shear values are high across that basin all year, even in summer. There are lesser pre-existing centers of rotation in the area.
  
  
• The Intertropical Convergence Zone (ITZC), which shifts north in the northern summer and south in the southern summer, typically remains at or near the equator. The tropospheric vertical wind shear is far too high, and there is rarely an inter-tropical convergence zone (ITCZ) over the ocean. It is extremely difficult to generate tropical cyclones without an ITCZ to provide synoptic vorticity and convergence, resulting in large-scale spin and thunderstorm activity, as well as strong wind shear.
  
  

Therefore, option (2) is the correct answer.

Subject: Geography | Climate Weather and Atmosphere