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The physics of ENSO-monsoon connection

Goswami, BN (1998) The physics of ENSO-monsoon connection. In: Indian Journal of Marine Sciences, 27 (01). pp. 82-89.

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The physical mechanism through which Ei-Nino and Southern Oscillation (ENSO) tends to produce deficient precipitation over Indian continent is investigated using both observations as well as a general circulation model. Both analysis of observations and atmospheric general circulation model (AGCM) study show that the planetary scale response associated with ENSO primarily influences the equatorial Indian Ocean region. Through this interaction it tends to favour the equatorial heat source, enhance precipitation over the equatorial Indian Ocean and indirectly cause a decrease in continental precipitation through induced subsidence. This situation is further complicated by the fact the regional tropospheric quasi biennial oscillation (QBO) has a bimodal structure over this region with large amplitude over the Indian continent. While the ENSO response has a quasi-four year periodicity and tends peak during beginning of the calendar year, the QBO mode tends to peak during northern summer. Thus, the QBO mode exerts a stronger influence on the interannual variability of the monsoon. The strength of the Indian monsoon in a given year depends on the combined effect of the ENSO and the QBO mode. Sines the two oscillations have disparate time scales, exact phase information of the two modes during northern summer is important in determining the Indian summer monsoon. The physical mechanism of the interannual variations of the Indian monsoon precipitation associated with ENSO presented here is similar to the physical process that cause intraseasonal 'active', 'break' oscillations of the monsoon.

Item Type: Journal Article
Publication: Indian Journal of Marine Sciences
Publisher: National Institute of Science Communication and Information Resources
Additional Information: Copyright of this article belongs to National Institute of Science Communication and Information Resources.
Department/Centre: Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited: 09 Dec 2009 12:14
Last Modified: 09 Dec 2009 12:14
URI: http://eprints.iisc.ac.in/id/eprint/19413

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