Model Answer
0 min readIntroduction
The Indian Monsoon, a defining feature of the Indian climate, profoundly impacts the socio-economic life of the country. It is not simply a wind system but a complex interplay of atmospheric and oceanic processes. The term ‘Monsoon’ is derived from the Arabic word ‘Mausim’, meaning seasonal winds. The monsoon contributes approximately 75-90% of the total rainfall in India, making its understanding crucial for agricultural planning, water resource management, and disaster preparedness. This answer will discuss the mechanism behind this vital climatic phenomenon, detailing its origin, progression, and influencing factors.
The Genesis of the Indian Monsoon
The Indian Monsoon is essentially a land and sea breeze on a large scale. Its origin can be traced to the differential heating of land and sea. During summer, the Indian subcontinent heats up rapidly, creating a low-pressure area. Simultaneously, the surrounding seas, particularly the Arabian Sea and the Bay of Bengal, heat up more slowly and remain relatively cooler, creating high-pressure areas.
Key Influencing Factors
1. Thermal Differences:
The intense heating of the Indian subcontinent leads to a significant pressure gradient, drawing in moisture-laden winds from the surrounding oceans. This differential heating is the primary driver of the monsoon circulation.
2. Shift of the Intertropical Convergence Zone (ITCZ):
The ITCZ, a low-pressure zone near the equator where trade winds converge, shifts northwards during the summer months following the apparent movement of the sun. This shift brings the ITCZ over the Indian subcontinent, attracting the south-westerly monsoon winds.
3. High-Pressure Systems:
The presence of the Mascarene High (over the South Indian Ocean) and the Tibetan High (over the Tibetan Plateau) plays a crucial role. The Mascarene High steers the south-westerly monsoon winds towards India, while the Tibetan High strengthens the upper air circulation and inhibits monsoon activity after September.
4. Jet Streams:
Subtropical Jet Stream: This jet stream flows over North India, causing tropical disturbances to move towards the east. Its weakening during summer allows the monsoon to establish itself. Tropical Easterly Jet Stream: This jet stream develops over peninsular India during summer and is crucial for the onset and maintenance of the monsoon.
5. Somali Jet:
The Somali Jet, a low-level jet stream over the Somali coast, is a crucial precursor to the onset of the monsoon. It strengthens as the land heats up and draws in moisture-laden winds from the Arabian Sea towards the Indian subcontinent.
The Monsoon Winds and their Branches
The south-west monsoon winds, originating from the Arabian Sea and the Bay of Bengal, split into four main branches upon reaching the Indian coast:
- The Arabian Sea Branch: Strikes the western coast of India (Kerala, Karnataka, Goa, Maharashtra) and brings heavy rainfall.
- The Bay of Bengal Branch: Splits into two branches – one moving towards West Bengal and the other towards Assam. The Assam branch causes heavy rainfall in the North-Eastern states.
- The Land Breeze Branch: After losing moisture, the Arabian Sea branch moves over the dry land and causes rainfall in Rajasthan, Haryana, and Punjab.
- The Eastern Branch: This branch moves along the eastern coast and causes rainfall in Odisha, Andhra Pradesh, and Tamil Nadu.
Seasonal Progression of the Monsoon
The monsoon arrives in India in stages:
- Onset (June): The monsoon typically arrives in Kerala around June 1st, gradually progressing northward.
- Advance (June-July): The monsoon covers most of India during this period, bringing widespread rainfall.
- Peak (July-August): The monsoon reaches its peak intensity, with heavy rainfall across the country.
- Retreat (September-October): The monsoon begins to withdraw from North-West India, leading to a decrease in rainfall. The retreating monsoon causes cyclonic disturbances along the eastern coast.
Monsoon Variability
The Indian Monsoon is known for its variability. Factors like El Niño-Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the Madden-Julian Oscillation (MJO) can significantly influence monsoon rainfall. A strong El Niño often leads to a deficient monsoon, while a positive IOD can enhance rainfall.
Conclusion
The Indian Monsoon is a complex climatic phenomenon driven by a combination of thermal differences, atmospheric pressure systems, and jet streams. Understanding its mechanism is vital for predicting rainfall patterns and mitigating the impacts of monsoon-related disasters. Increasingly, climate change is impacting monsoon patterns, leading to more frequent and intense extreme weather events. Therefore, continued research and improved forecasting capabilities are crucial for ensuring water security and sustainable development in India.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.