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A mechanism for the west-north-west movement of monsoon depressions

Goswami, BN (1987) A mechanism for the west-north-west movement of monsoon depressions. In: Nature, 326 (6111). pp. 376-378.

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The monsoon depressions intensify over the Bay of Bengal, move in a west-north-west (WNW) direction and dissipate over the Indian continent. No convincing physical explanation for their observed movement has so far been arrived at, but here, I suggest why the maximum precipitation occurs in the western sector of the depression and propose a feedback mechanism for the WNW movement of the depressions. We assume that a heat source is created over the Bay of Bengal due to organization of cumulus convection by the initial instability. In a linear sense, heating at this latitude (20° N), produces an atmospheric response mainly in the form of a stationary Rossby–gravity wave to the west of the heat source. The low-level vorticity (hence the frictional convergence) and the vertical velocity associated with the steady-state response is such that the maximum moisture convergence (and precipitation) is expected to occur in the WNW sector at a later time. Thus, the heat source moves to the WNW sector at a later time and the feedback continues resulting in the WNW movement of the depressions.

Item Type: Journal Article
Publication: Nature
Publisher: Macmillan
Additional Information: Copy right of this article belongs to Macmillan.
Department/Centre: Division of Mechanical Sciences > Centre for Atmospheric & Oceanic Sciences
Date Deposited: 19 Jan 2010 07:56
Last Modified: 19 Sep 2010 05:37
URI: http://eprints.iisc.ac.in/id/eprint/21528

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