What is Monsoon and what causes it?

What is monsoon

Monsoon is seasonal wind. It can be both dry and wet, although the later is more widely known.

What causes monsoon?

Basic concept: Hadley cells and ITCZ

Hadley cell is tropical atmospheric circulation and intertropical convergence zone (ITCZ) is a low air pressure zone. ITCZ is very clear in a map of cloud or precipitation.

A schematic figure from Wikipedia

Another figure from IPCC AR6

Monsoon is seasonal shift of air pressure bands.

In boreal summer, land is warming faster than ocean, which leads to the northward movement of ITCZ. This brings the trade wind with moisture which convert to precipitation.

In austral summer, ITCZ moves southward. This causes the wet season of Southern Australia and the dry season of Indian subcontinent.