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Published February 2017 | Published + Supplemental Material
Journal Article Open

Intraseasonal rainfall variability in the Bay of Bengal during the Summer Monsoon: coupling with the ocean and modulation by the Indian Ocean Dipole

Abstract

The Indian Summer Monsoon rainfall exhibits pronounced intraseasonal variability in the Bay of Bengal (BoB). This study examines the intraseasonal rainfall variability with foci on the coupling with sea surface temperatures (SST) and its interannual modulation. The lagged composite analysis reveals that, in the northern BoB, SST warming leads the onset of intraseasonal rainfall by 5 days. Latent heat flux is reduced before the rain event but is greatly amplified during the rainfall maxima. Further analysis reveals that this intraseasonal rainfall-SST relationship through latent heating is strengthened in negative Indian Ocean Dipole (IOD) years when the bay-wide local SST is anomalously warm. Latent heat flux is further increased during the intraseasonal rainfall maxima leading to strengthened rainfall variability. The moisture budget analysis shows this is primarily due to stronger low-level moisture convergence in negative IOD years. The results provide important predictive information on the monsoon rainfall and its active/break cycles.

Additional Information

© 2017 The Authors. Atmospheric Science Letters published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Issue online: 1 February 2017; Version of record online: 24 January 2017; Manuscript Accepted: 15 December 2016; Manuscript Revised: 9 December 2016; Manuscript Received: 26 August 2016. This project is part of SJ's Summer Student Fellowship (SSF) program at Woods Hole Oceanographic Institution (WHOI) sponsored by the National Science Foundation Research Experience for Undergraduates Program (NSF-REU). HS acknowledges grants from the Office of Naval Research (N00014-15-1-2588) and National Oceanic and Atmospheric Administration (NA15OAR4310176). CCU acknowledges support from the National Science Foundation under AGS-1304245. The authors thank two anonymous reviewers for their constructive comments, which helped to substantially improve the manuscript.

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Published - Jongaramrungruang_et_al-2017-Atmospheric_Science_Letters.pdf

Supplemental Material - asl2729-sup-0001-AppendixS1.pdf

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