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On the anomalous precipitation enhancement over the Himalayan foothills during monsoon breaks

Vellore, RK and Krishnan, R and Pendharkar, J and Choudhury, AD and Sabin, TP (2014) On the anomalous precipitation enhancement over the Himalayan foothills during monsoon breaks. Climate Dynamics, 43 (7-8). pp. 2009-2031.

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An intriguing feature associated with 'breaks' in the Indian summer monsoon is the occurrence of intense/flood-producing precipitation confined to central-eastern parts of the Himalayan (CEH) foothills and north-eastern parts of India. Past studies have documented various large-scale circulation aspects associated with monsoon-breaks, however the dynamical mechanisms responsible for anomalous precipitation enhancement over CEH foothills remain unclear. This problem is investigated using diagnostic analyses of observed and reanalysis products and high-resolution model simulations. The present findings show that the anomalous precipitation enhancement over the CEH foothills during monsoon-breaks emerges as a consequence of interactions between southward intruding mid-latitude westerly troughs and the South Asian monsoon circulation in its weak phase. These interactions facilitate intensification of mid-tropospheric cyclonic vorticity and strong ascending motion over the CEH foothills, so as to promote deep convection and concentrated rainfall activity over the region during monsoon-breaks. Mesoscale orographic effects additionally tend to amplify the vertical motions and precipitation over the CEH foothills as evidenced from the high-resolution model simulations. It is further noted from the model simulations that the coupling between precipitation and circulation during monsoon-breaks can produce nearly a threefold increase of total precipitation over the CEH foothills and neighborhood as opposed to active-monsoon conditions.

Item Type: Article
Additional Information: Copyright of this article belongs to Springer.
Uncontrolled Keywords: Monsoon-breaks;Westerly trough;Himalayan foothills; Flood-producing precipitation
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 04 Dec 2014 09:33
Last Modified: 04 Dec 2014 09:33

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