Extended Data Fig. 3: The time series of climate indices.
a–d, The time series of the IOD index (difference of the area-averaged SST over 50–70° E, 10° S–10° N from that over 90–110° E, 15°–0° S) during the SON season (a), the Indian Ocean Basin-wide warming (IOBW) index (area-averaged SST over 40–110° E, 15° S–10° N) during the JFM season (b), the Western Hemispheric Warm Pool (WHWP) index (area-averaged SST over 60–105° E, 10–35° N) during the MJJ season (c), and the Pacific Meridional Mode (PMM) index (first Maximum Covariance Analysis (MCA) principal components over the 175° E–95° W, 21° S–32° N using SST and 10-m winds) during the DJF season (d). The values preceding the 1997/98 El Niño event are denoted by the red star when the value is positive and the blue star when the value is negative.
