monsoon

Expressed indistinctly in singular and plural (monsoons), it is the bimodal wind regime that blows in some regions of the tropical and subtropical realm, linked to the seasonal shifting of the ITCZ (Intertropical Convergence Zone) and to the appearance in South Asia of the equatorial jet (easterly current) in the upper troposphere (between 15 and 17 km of altitude at the equator). These persistent winds are a consequence of the differential heating experienced by continental areas and neighboring oceanic ones, and they reverse direction - blowing alternately from the southwest and northeast - depending on whether it is summer or winter. The word monsoon derives from the Arabic term mausim, meaning season, precisely because of the referenced seasonal change of direction. It is very common to identify the monsoon with the rainy season in India, which corresponds only to the summer monsoon in that country. The southwest winds, heavily laden with moisture as a consequence of their maritime path over the Bay of Bengal, on reaching land bring torrential and persistent rains to northeast India and Bangladesh, causing floods. The monsoon regime also extends to other areas of Southeast Asia, as well as of America, Africa, and Oceania. In all these places, there is an alternation between the summer monsoon (southwest winds) and the winter monsoon (northeast winds). Monsoon rains fall mainly over dry land during the summer season.