Evolution of Tripole Pattern of Sea-Level Anomalies in the Indian Ocean During Concurrent ENSO-IOD Episodes

This study examines the sea-level variability over the Indian Ocean by using Empirical Orthogonal Function (EOF) analysis and concentrates on the first two leading modes of variability over the region. The first mode shows the dipole pattern, whereas the second mode has a tripole pattern. It is observed that the principal component corresponding to the first mode (PC1) leads the principal component of the second mode (PC2) by five months. Seasonal reliant EOF and cross-correlation analysis support this relationship between PC1 and PC2. The second EOF mode is temporally emerging from the first mode in conditional climate variability. It is found that during concurrent El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events, EOF-2 mode appears from EOF-1 and hence is conditionally dependent.