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Difficulty: Very hardClimate, Weather Systems, and Monsoon of India

With reference to the atmospheric driving forces and mechanisms of the Indian Southwest Monsoon, consider the following statements:

1. The seasonal northward movement of the Inter-Tropical Convergence Zone (ITCZ) over the Ganga Plain establishes the thermal monsoon trough essential for drawing cross-equatorial winds.
2. The Tropical Easterly Jet (TEJ), positioned over the Indian Peninsula near 13∘N13^\circ\text{N} latitude during summer, facilitates upper-level divergence that reinforces the lower-level surface low-pressure system.
3. The intensification and position of the Mascarene High near the East African coast directly strengthen the cross-equatorial Somali Jet and the resultant moisture transport to the Indian subcontinent.
4. The Somali Jet is an upper-tropospheric westerly wind stream that impedes the inflow of moisture-laden Arabian Sea winds towards the Western Ghats.

Which of the statements given above are correct?

  1. 1, 2, and 3 onlyAnswer
  2. B
    1 and 2 only
  3. C
    2, 3, and 4 only
  4. D
    1, 3, and 4 only

Answer

Statements 1, 2, and 3 are correct, while statement 4 is incorrect because the Somali Jet is a low-level (not upper-tropospheric) cross-equatorial jet stream that transports massive moisture to India.
The option selecting statements 1, 2, and 3 only is correct because the northward movement of the ITCZ, upper-air divergence from the Tropical Easterly Jet, and the strong pressure gradient from the Mascarene High collectively establish the Indian southwest monsoon. The option incorrectly stating that the Somali Jet is an upper-tropospheric jet that impedes moisture is false, as the Somali Jet is low-level and strengthens monsoon rainfall.

Step-by-Step Solution

1
Analyze Statement 1 regarding ITCZ shift
Statement 1 is correct.
During northern summer, the ITCZ shifts northward over the Ganga plain (around 20∘N20^\circ\text{N}–25∘N25^\circ\text{N}), forming the equatorial trough of low pressure known as the monsoon trough.
2
Analyze Statement 2 regarding Tropical Easterly Jet (TEJ)
Statement 2 is correct.
The heating of the Tibetan Plateau gives rise to the Tropical Easterly Jet stream in the upper troposphere, creating upper-level divergence over South India which draws lower-level monsoon winds.
3
Analyze Statement 3 regarding Mascarene High
Statement 3 is correct.
A high-pressure cell near Madagascar (30∘S30^\circ\text{S}, 60∘E60^\circ\text{E}) acts as the Southern Hemisphere pressure origin; its strength correlates directly with strong cross-equatorial pressure gradients and monsoon rainfall.
4
Analyze Statement 4 regarding the Somali Jet
Statement 4 is incorrect.
The Somali (Findlater) Jet is a low-level jet stream (around 1.5 km1.5\text{ km} or 850 hPa850\text{ hPa}) off the horn of Africa, driving intense moisture-laden Arabian Sea winds towards western India, not an upper-tropospheric jet impeding moisture flow.

Key Concept

Modern Thermal and Dynamic Theories of the Indian Southwest Monsoon
Estimated Time:2m 0s
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Topics

Climate, Weather Systems, and Monsoon of India

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