Explanation: The air at the Inter Tropical Convergence Zone (ITCZ) rises because of convection caused by high insolation and a low pressure is created.

• The winds from the tropics converge at this low pressure zone. The converged air rises along with the convective cell.
• It reaches the top of the troposphere up to an altitude of 14 km. and moves towards the poles. This causes accumulation of air at about 30o N and S.
• Part of the accumulated air sinks to the ground and forms a subtropical high.
• Another reason for sinking is the cooling of air when it reaches 30o N and S latitudes. Down below near the land surface the air flows towards the equator as the easterlies.
• The easterlies from either side of the equator converge in the Inter Tropical Convergence Zone (ITCZ).
• Such circulations from the surface upwards and vice-versa are called cells. Such a cell in the tropics is called Hadley Cell.

Source: NCERT – Fundamental of Physical Geography