Fig. 4 | Nature Communications

Fig. 4

From: A model for super El Niños

Fig. 4

Amplitude of convective variations during selected IOD and El Niño events. The shaded curve shows root mean amplitude of squared outgoing longwave radiation (OLR) anomaly over the Indian Ocean for a 1997, b 2015, c 2006, and d 1994; the solid lines are the same, but for the Pacific Ocean. We used daily anomalies that were were low-pass filtered to retain only periodicities longer than 90 days. At each grid point, these anomalies were squared. Then, their area averages were computed over the tropical (20°S–20°N) Indian (40°E–120°E) and Pacific (140°E–280°E) Oceans—the square root of these areal averages is shown. During ENSO and IOD events, convective anomalies are not of a single sign, neither over the tropical Pacific Ocean, nor over the tropical Indian Ocean. For example, a positive IOD event is associated with negative OLR anomaly over the central tropical Indian Ocean and positive OLR anomaly over the eastern tropical Indian Ocean. The use of squared OLR anomalies capture the amplitude of both phases of OLR variations during IOD or ENSO events in a single OLR index

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