Understanding Indian Monsoon Breaks and Rainfall Patterns

This solution explains the typical weather patterns observed during a 'break' in the Indian monsoon, specifically focusing on which regions continue to receive significant rainfall. A monsoon break signifies a period where the monsoon's intensity decreases, leading to reduced rainfall, particularly over the central and southern parts of India.

What is a Monsoon Break?

• A 'break' in the Indian monsoon refers to a weather phenomenon characterized by a significant reduction in rainfall over most parts of the Indian plains and the peninsula.
• During these breaks, the intensity of the monsoon weather system weakens considerably.
• These breaks can last for a few days to a couple of weeks.

The Role of the Monsoon Trough

The Indian monsoon system is closely associated with the monsoon trough, a low-pressure line that generally runs from the Pakistani coast, through the plains of Northwest India, towards the Bay of Bengal. The position and intensity of this trough largely determine the distribution of rainfall across the country.

• Active Monsoon Phase: When the trough is active and positioned south of its usual location (over the plains), it draws moisture from the Arabian Sea, leading to heavy rainfall along the west coast (Konkan, Western Ghats) and widespread rain over the northern plains.
• Monsoon Break Phase: During a break, the monsoon trough tends to weaken and shift its position. Often, it moves northwards towards the Himalayan foothills.

Rainfall Distribution During a Northward Shift

When the monsoon trough shifts northwards towards the Himalayas, the atmospheric conditions change:

• Rainfall decreases significantly over the plains and peninsular regions because they are no longer under the influence of the main trough.
• However, the areas near the shifted trough, specifically the Himalayan Foothills and adjoining regions like parts of Northeast India, often experience increased or continued rainfall. This is because the trough's northern position facilitates moisture convergence and uplift in these areas.
• Northeast India also receives moisture from the Bay of Bengal branch of the monsoon, which can sometimes maintain rainfall even when the Arabian Sea branch (affecting the west coast and central India) weakens during a break.

Analysis of Options

Let's examine why certain areas receive less rain and others continue to get rain during a monsoon break characterized by a northward shift:

• The Konkan Coast and Western Ghats: These areas are heavily dependent on the Arabian Sea branch of the monsoon. During a break, especially with a northward trough shift, rainfall here significantly reduces.
• The Southern Interior Karnataka Plateau: This region is often drier compared to the west coast. While it receives monsoon rains, it is not typically the area that sees increased rainfall during a monsoon break when the trough moves north.
• The semi-arid regions of Gujarat and Rajasthan: These regions generally receive less monsoon rainfall compared to the core monsoon areas. A northward shift of the trough usually means less moisture reaching these western parts of the country, leading to reduced rainfall.
• The Himalayan Foothills and parts of Northeast India: This region aligns with the meteorological conditions during a monsoon break when the trough shifts north. The convergence of moist winds along the foothills and the Bay of Bengal's influence on Northeast India results in continued rainfall here, even as other parts of the country dry up.

Conclusion

Therefore, during an Indian monsoon break, marked by reduced rainfall over the plains and peninsular India and a northward shift of the monsoon trough, the Himalayan Foothills and parts of Northeast India are the regions that typically continue to experience notable rainfall.