Abstract
The Indian Ocean Zonal Mode (IOZM), also referred as Indian Ocean
Dipole Mode, is one dominant pattern of
interannual variabilities of the Indian Ocean. The generation mechanism
of this mode is not well understood. Some hypotheses postulate that
this mode is forced by ENSO, but others suggest that this mode results
from the air-sea interactions of the Indian Ocean itself. These
hypotheses suggest very different ENSO-IOZM relationship. This study
performs experiments with a coupled atmosphere-ocean general
circulation model (CGCM) to investigate this relationship. Two CGCM
simulations are performed. One includes both the Indian and Pacific
Oceans in the ocean model component (i.e., the Indo-Pacific Run). The
other simulation includes only the Indian Ocean in the ocean model
component (i.e., The indian-Ocean Run). The Indo-Pacific Run is
integrated for 100 years and the Indian-Ocean Run is integrated
for 50 years.
The Indo-Pacific Run simulates ENSO events realistically and produces
strong decade-to-decade ENSO changes. Both this run and the
Indian-Ocean Run simulate the Indian Ocean Zonal mode but with
different dominant timescales. These results suggest that the coupled
Indian Ocean-Monsoon system itself is capable of producing the Indian
Ocean dipole mode without the forcing from ENSO. However, ENSO is
capable of changing the dominanted timescales of the Indian Ocean
dipole mode.
Related Publications
Yu, J.-Y. and K. M. Lau,
2004: Contrasting Indian
Ocean SST variability with and without ENSO influence: A coupled
atmosphere-ocean GCM study. Meteorology and Atmospheric
Physics, DOI: 10.1007/s00703-004-0094-7.
Yu, J.-Y., S.-P. Weng, and
J. D. Farrara, 2003: Ocean
Roles in the TBO Transitions of the Indian-Australian Monsoon
System. Journal of Climate, 16, 3072-3080.
Yu, J.-Y., C. R. Mechoso, J. C. McWilliams, and A. Arakawa 2002: Impacts of the Indian Ocean on the ENSO cycle. Geophysical Research
Letters, 29(8), 1204, doi:10.1029/2001GL014098.
