Trenberth, K. E. (1997) The Definition of El Niño

Bull. Amer. Meteor. Soc., 78, 2771-2777.


Figure 1 shows time series plots of the Niño 3 (upper) and Niño 3.4 (lower) SST indices as five month running means using data from NOAA and relative to a base period climatology from 1950-1979. Values above thresholds of ±0.5°C for Niño 3 and ±0.4°C for Niño 3.4 are stippled to indicate ENSO events. The Niño 3 Region is bounded by 90°W-150°W and 5°S- 5°N. The Niño 3.4 Region is bounded by 120°W-170°W and 5°S- 5°N.