Multi-decadal Variability in Indian Summer Monsoon Rainfall: Some New Perspectives


B. Goswami

13:50:00 - 14:40:00

101 , Mathematics Research Center Building (ori. New Math. Bldg.)

Based on the observational data for the 1871-2000 period the Indian Summer Monsoon Rainfall (ISMR) exhibited neither a significant trend nor any impact of climate change, but a quasi-60-year periodicity with alternate epochs (~30 years) of above and below normal rainfall. However, the recent decade of 2001-2010 has changed this scenario significantly. While the ISMR displays a weak decreasing trend for the entire observational data period (1871-2011), the last 6 decades show a strong decreasing trend significant at 99% confidence level. Thus, the existence of a quasi-60-year periodicity is not a robust feature limiting the predictability of multi-decadal variability of ISMR. Possible drivers for the multi-decadal variability of ISMR are explored with special emphasis on understanding the drivers for the recent decreasing trend in the ISMR.

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