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It is now well recognized that the El Niño/Southern Oscillation (ENSO) phenomenon is the single most important cause of year-to-year climatic variability. Several studies have documented that a majority of the warm extremes (El Niño events) cause below-normal rainfall over Indonesia, while cold extremes (La Niña events) cause above-normal rainfall over India.
During the current ongoing El Niño episode, temperature anomalies in the Niño 1+2, Niño 3, and Niño 3.4 regions have been the largest values observed in the last 50 years. The pattern of anomalous tropical convection with enhanced activity across the central and eastern equatorial Pacific and suppressed convection over the Indonesian and western Pacific has prevailed since March 1997. This has resulted in drought over Indonesia. Much of Indonesia is suffering its worst drought in 50 years as a result of the effects of the latest El Niño system on weather. However, during this episode, the June–September Indian monsoon rainfall (IMR) was normal—102% of the long-term average. In fact, some regions experienced severe floods. We propose a new hypothesis to explain this.