ESRL/PSD Seminar Series

More frequent monsoon failure due to inherent instability

LaJacob Schewe
More frequent monsoon failure due to inherent instability


Indian summer monsoon rainfall is vital for a large share of the world's population. Both reliably projecting India's future rainfall and unraveling abrupt monsoon shifts found in paleo-records require improved understanding of its stability properties. Here we project monsoon failure to become considerably more frequent due to global warming, and provide a simple dynamical explanation for this trend as well as for multi-decadal rainfall variability. Based on fundamental properties of observed monsoon dynamics and an associated inherent instability that is modulated by ambient climate merely during the onset period, we develop a statistically predictive model of seasonal rainfall. Forced only by global mean temperature and central-Pacific sea level pressure anomalies in May, this simple model reproduces past and future monsoon trends as found in a comprehensive climate model. We thereby propose a novel perspective on monsoon variability as the result of internal instabilities modulated by pre-seasonal ambient climate conditions.

Wednesday, November 9, 2011

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