The Complementary Influences of the Indian Ocean Dipole and the ENSO on the Variability of the Indian Summer Monsoon Rainfall
K. Ashok, Z. Guan and T. Yamagata
Frontier Research System for Global Change (FRSGC)
Tokyo, Japan
From the analysis of the observed rainfall over India from 1958-1997, we discovered the interesting fact that the ENSO and the Indian Ocean Dipole (IOD) influence the Indian Summer Monsoon Rainfall (ISMR) in a complementary fashion. When the ENSO-ISMR correlation was strong till the late eighties, the correlation between the ISMR and the IOD was weak. As the ENSO-ISMR correlation became weaker, that between the IOD-ISMR has become stronger. We found that IOD can modulate the ENSO influence on ISMR, depending on its (IOD's) intensity and sign. Our sensitivity experiments carried out using the AGCM show that IOD can influence the ISMR by modulating the cross-equatorial Hadley circulation.
