The composite averages of rainfall anomalies over Thailand for weak-ENSO periods, strong-ENSO periods and their differences are presented in figure 5. There was high rainfall in the cold phase (La Nina) [30] especially in the southern part of Thailand during the weak and strong periods, as shown in figures 5(a) and 5(b). There was low rainfall in the warm phase (El Nino) [30] especially in the southern part of Thailand during the weak and strong periods, as shown in figures 5(c) and 5(d). The differences between the La Nina and El Nino rainfall anomalies during the weak and strong periods are shown in figures 5(e) and 5(f). These differences were higher during the weak-ENSO periods than during the strong-ENSO periods.
Nino 3.4
NOAA uses SST index for identifying El Niño (warm) and La Niña (cool) events in the tropical Pacific. It is the seasonal mean SST anomaly for the Niño3 region (5°N to 5°S and 150°W to 90° W) and the Niño3.4 region (5°N to 5°S and 170°W to 120°W). Events are defined above the +0.4°C anomaly for warm (El Niño) events and at or below the -0.4°C anomaly for cold (La Niña) events for Niño 3. Events are defined above the +0.5°C anomaly for warm (El Niño) events and at or below the -0.5°C anomaly for cold (La Niña) events for Niño 3.4.The threshold is further broken down into Weak (with a 0.5°C to 0.9°C SST anomaly), Moderate (1.0°C to 1.4°C) and Strong (≥ 1.5°C) events. For the purpose of this report for an event to be categorized as weak, moderate or strong (Jan Null, 2015).