The head of the Bay of Bengal
Explanation
The spatial distribution and intensity of rainfall during the Southwest Monsoon season are significantly influenced by the frequency and path of low-pressure systems, known as tropical depressions or monsoon depressions.
Detailed Analysis:
- Formation at the Head of the Bay of Bengal: These depressions typically originate at the head of the Bay of Bengal. Their formation is linked to the position of the Inter-Tropical Convergence Zone (ITCZ), also known as the monsoon trough, over the Gangetic plains.
- Movement and Rainfall Distribution: After forming, these depressions generally move in a west-northwest direction across the Indian mainland. As they travel along the monsoon trough, they bring substantial rainfall to the central and northern regions of India.
- Role of Other Regions:
- Arabian Sea: While cyclonic systems do form in the Arabian Sea, the specific "monsoon depressions" that traverse the Indian landmass and sustain the monsoon rains primarily originate in the Bay of Bengal.
- Indian Ocean South of the Equator: This region is the source of the high-pressure cell (Mascarene High) that drives the monsoon winds, but it is not the genesis ground for the depressions affecting the Indian mainland.
Key Takeaway:
The tropical depressions that govern the active phase of the monsoon rains generally form at the head of the Bay of Bengal and move northwestwards across the country.