Interaction Between the Indian Ocean Dipole and ENSO Associated with Ocean Subsurface Variability

The Indian Ocean dipole (IOD) is an intrinsic coupled mode of variability in the tropical Indian Ocean. It has broad impacts on regional climate. An IOD index is defined as the difference between sea surface temperature (SST) anomalies averaged over the western Indian Ocean (WIO, 50°–70°E, 10°S– 10°N) and eastern Indian Ocean (EIO, 90°– 110°E, 10°S–Eq.). An important issue in the studies of IOD is the relationship between IOD and the El Niño-Southern Oscillation (ENSO) and the potential feedbacks from each other. Previous studies have shown that the development of IOD can be independent of ENSO, but ENSO may exert significant influence. In recent years, it has also been found that IOD can affect ENSO. Clearly, there exists an intimate interaction between IOD and ENSO but the detailed phenology of their mutual evolution has not been reported thus far.