Correct Option (b):
Tropical cyclones require specific atmospheric and oceanic conditions for their formation and intensification. A crucial factor is the presence of a pre-existing low-pressure disturbance, which often originates within the Inter-Tropical Convergence Zone (ITCZ). The ITCZ provides the necessary convergence, atmospheric instability, and cyclonic vorticity to initiate the development of tropical depressions.
In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, the ITCZ is typically weak, ill-defined, or absent for significant periods. This lack of a robust ITCZ means there is insufficient organized convection and cyclonic rotation to foster the genesis of tropical cyclones. Furthermore, these regions often experience strong vertical wind shear, which disrupts the vertical organization of developing storm systems, preventing them from strengthening into mature cyclones.
Incorrect Options:
(a) Sea surface temperatures are low: While cold ocean currents (e.g., Benguela Current in the South Atlantic, Peru Current in the South-Eastern Pacific) can lead to comparatively cooler sea surface temperatures in parts of these regions, these temperatures are not consistently low enough across the entire tropical belt to be the primary or sole reason for the complete absence of cyclones. Other factors, particularly the ITCZ's absence, are more dominant.
(c) Coriolis force is too weak: The Coriolis force is essential for initiating the rotational motion of cyclones. It is weak at the equator but increases with latitude. In tropical latitudes away from the equator, the Coriolis force is sufficiently strong to support cyclone formation. Its weakness is not a limiting factor in these specific regions.
(d) Absence of land in those regions: Tropical cyclones are oceanic phenomena. They form and intensify over warm ocean waters and do not require the presence of land for their genesis. In fact, land interaction typically weakens or dissipates cyclones.