Abstract Author: Annalisa Bracco, Fred Kucharski, Jin Ho Yoo and Franco Molteni
Abstract Title: Modulation of Indian Summer rainfall by tropical Atlantic forcing
Abstract: The interannual variability of the Indian Monsoon is modulated by the El Nino Southern Oscillation (ENSO), with a drier than normal monsoon season usually preceding peak El Nino conditions, possibly causing severe droughts over the Indian subcontinent, and vice versa for La Nina phase.
Pacific sea surface temperature (SST) anomalies, however, are not the only player: Atmospheric teleconnections between the tropical Atlantic and the Indian basin contribute to the modulation of the monsoon variability. Using two observational data sets and two ensembles of simulations over the period 1950-1999 we show that the residual in the Indian Monsoon Rainfall (IMR) time series for observed and modeled data, obtained by subtracting the ENSO-forced component of the IMR that is linearly related to the NINO34 index, is significantly correlated with south equatorial Atlantic SSTs and we discuss the physical motivation for such correlation. Our results have important implications for seasonal forecast efforts.