Mechanism of Onset of Indian Monsoon

1. Differential Heating of Land and Water- Since Indian continent lies near too equator and is surrounded by water on three sides. During summers, land is heated due faster as compared to water creating a low pressure and a high pressure system respectively.

1. Inter Tropical Convergence Zone- Inter Tropical Convergence Zone (ITCZ) is the region near equator where trade winds from both the hemispheres collide. During summer season the ITCZ moves northwards approaching the Indian subcontinent, bringing large amount of water from the Indian Ocean. This movement of ITCZ plays a significant role in onset of monsoon.

1. Heating of Tibetan Plateau- The extreme heating of Tibetan plateau leads to formation of low pressure over the same and a permanent high pressure in southern part of Indian Ocean.

1. Jet Streams- The movement of ITCZ is associated with withdrawal of westerly jet stream from its position. This causes the onset of Somali Jet along 15°N at the former place of westerly jet.

Due to occurrence of above mentioned phenomena, the monsoon wind system originates. After hitting the tip of peninsula it breaks into two branches i.e. Arabian Sea branch (south-west monsoon) and Bay of Bengal branch (north-east branch).

ENSO stands for El Nino-Southern Oscillation. It is a recurring climatic phenomenon. During El Nino years, droughts are observed while El Nina years bring above average rainfall.