Monsoon breaks and subseasonal sea surface temperature variability in the Bay of Bengal

Gabriel Andres Vecchi, D. E. Harrison

Research output: Contribution to journalArticle

166 Scopus citations

Abstract

The Indian southwest monsoon directly affects the lives of over one billion people, providing almost 90% of the annual precipitation to the Indian subcontinent. An important characteristic of the southwest monsoon is variability on subseasonal timescales, with "active" periods of heavy rain interrupted by drier "break" periods. Both the number of monsoon breaks in a season and the timing of these breaks profoundly impact agricultural output from the Indian subcontinent. Most research on monsoon breaks has emphasized possible atmospheric mechanisms. However, new satellite data reveal large-amplitude basin-scale subseasonal sea surface temperature (SST) variability in the Bay of Bengal (BoB), in which northern BoB cooling precedes monsoon breaks by about 1 week. The relationship is statistically significant at the 95% level over the 3 yr examined, and so offers a potential statistical predictor for short-term monsoon variability. The basinwide averaged amplitude of SST changes is 1°-2°C and local changes can exceed 3°C over 2 weeks; these changes are as large as those seen in the local climatological seasonal cycle. This raises the possibility that air-sea interaction may be a significant factor in monsoon variability: the SST variability is coherent with monsoon variability with a phase relationship consistent with a coupled oscillation. A schematic coupled air-sea oscillator mechanism is offered for further study, in which oceanic changes play a dynamical role in monsoon variability.

Original languageEnglish (US)
Pages (from-to)1485-1493
Number of pages9
JournalJournal of Climate
Volume15
Issue number12
DOIs
StatePublished - Jun 15 2002

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

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