  The initiation of the Indian summer monsoon circulation during late May /
early June arises through large-scale land-sea thermal contrast and setting up
of negative pressure gradient between the Monsoon Trough over the Indo-Gangetic
plains and the Mascarene High over the subtropical Indian Ocean. The meridional
pressure gradient together with the Earth's rotation (Coriolis force) creates
the summer monsoon cross-equatorial flow, while feedbacks between
moisture-laden winds and latent heat release from precipitating systems
maintain the monsoon circulation during the June-September (JJAS) rainy season
(Krishnamurti and Surgi, 1987). This simplified view of the Indian monsoon is a
useful starting point to draw insights into the variability of the large-scale
monsoon circulation.
