The sun shines almost vertically on the equator throughout the year.
As a result the air gets warm and rises over the equatorial region and produce equatorial low pressure.
This belt extends from equator to 100N and 100S latitudes.
Due to excessive heating horizontal movement of air is absent here and only conventional currents are there.
Therefore this belt is called doldrums (the zone of calm) due to virtual absence of surface winds.
These are the regions of convergence because the winds flowing from sub tropical high pressure belts converge here.
This belt is also known as-Inter Tropical Convergence Zone (ITCZ).