The monsoon system: Land–sea breeze or the ITCZ?

• Published in: Journal of Earth System Science Vol. 127; no. 1; pp. 1 - 29
• Main Author: Gadgil, Sulochana
• Format: Journal Article
• Language: English
• Published: New Delhi Springer India 01.02.2018; Springer Nature B.V
• Subjects: Earth and Environmental Science; Earth Sciences; Equatorial trough; Hypotheses; Intertropical convergence zone; Land-sea breezes; Migration; Monsoons; Precipitation; Sea breezes; Seasons; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Summer; Summer monsoon; Surface temperature; Variability; Wind; India; intertropical convergence zone; monsoonal regions; equatorial trough; Indian summer monsoon; heat lows
• ISSN: 0253-4126; 0973-774X
• DOI: 10.1007/s12040-017-0916-x

For well over 300 years, the monsoon has been considered to be a gigantic land–sea breeze driven by the land–ocean contrast in surface temperature. In this paper, this hypothesis and its implications for the variability of the monsoon are discussed and it is shown that the observations of monsoon variability do not support this popular theory of the monsoon. An alternative hypothesis (whose origins can be traced to Blanford’s ( 1886 ) remarkably perceptive analysis) in which the basic system responsible for the Indian summer monsoon is considered to be the Intertropical Convergence Zone (ITCZ) or the equatorial trough, is then examined and shown to be consistent with the observations. The implications of considering the monsoon as a manifestation of the seasonal migration of the ITCZ for the variability of the Indian summer monsoon and for identification of the monsoonal regions of the world are briefly discussed.