ITCZ stands for the Inter-Tropical Convergence Zone and is also known as the doldrums. It is the zone of convergence of the northeast and southeast trade winds. The region is a low pressure zone between the tropics and moves north and south of equator with the apparent shift in the position of the sun. The heating by the sun causes the air to rise which is replaced by the trade winds. The region is characterised by light winds and heavy rainfall.
While the Indian monsoon is primarily attributed to differential heating of land and ocean, the alternative theory lays more emphasis on the shifting of the ITCZ according to the position of the sun. The low pressure zone north of the equator during the summer in the northern hemisphere sees the convergence of trade winds. The south-east trade winds carry moisture and are deflected to their right in the northern hemisphere due to Coriolis effect. This translates into moist south-west winds that cause monsoon rainfall over the Indian subcontinent.