DRAFT The Monsoon as a Self-regulating Coupled Ocean-Atmosphere System

Observational studies have shown that the Asian-Australasian monsoon system exhibits variability over a wide-range of space and time scales. These variations range from intraseasonal (20–40 days), annual, biennial (about 2 years), longer term interannual (3–5 years) and interdecadal. Despite this range of variability, the South Asian monsoon (at least as described by Indian precipitation) exhibits a smaller range of variability during its summer pluvial phase than variability exhibited in other climate systems of the tropics. For example, drought or flood rarely extend to multiple years, with rainfall oscillating biennially from slightly above average to slightly below average precipitation. We argue that variability of the monsoon is regulated by negative feedbacks between the ocean and the atmosphere. The annual cycle of the heat balance of the Indian Ocean is such that there is an ocean heat transport from the summer hemisphere from the summer hemisphere resulting principally from wind-driven Ekman transport. Given the configuration of the low-level monsoon winds, the Ekman transport is in the opposite sense to the lower tropospheric divergent wind. The cross-equatorial ocean heat transport is large with amplitude