Diverse impact of 2023 El Niño on weather patterns over the Indonesian Maritime Continent

Abstract

The El Niño–Southern Oscillation (ENSO) significantly affects climate extremes, particularly causing the driest conditions across the Indonesian Maritime Continent (IMC). However, the specific impacts of the 2023 ENSO on weather pattern anomalies in the IMC have not been thoroughly explored. This study examines the 2023 El Niño, one of the strongest El Niño conditions during the warmest climate decade, and its effects on weather anomalies (i.e. hot and humid) to fill gaps in our understanding of the diverse impacts of ENSO in the IMC. Composite analysis (1991–2023) from the European Centre for Medium-Range Weather Forecasts Reanalysis v5 (ERA5) and National Oceanic and Atmospheric Administration datasets demonstrated that the 2023 El Niño strengthened westerly winds across the Pacific Ocean and influenced intraseasonal rainfall patterns over the IMC. Distinct contrasts were observed between northern (DOM1) and southern (DOM2) IMC. During the onset and mature periods of El Niño (April–September 2023), DOM2 experienced reduced rainfall and significant drought, especially during the dry season (June–September 2023), affecting vital agricultural regions in Java and southern Sumatra. The positive Indian Ocean Dipole and vigorous Australian monsoon likely intensified this drought. Conversely, DOM1 experienced increased rainfall, triggering severe flood events in several regions in Sumatra and Kalimantan (i.e. northern Sumatra and western, northern and central Kalimantan). Our findings highlighted that the enhanced rainfall, driven by middle and high cloud activities, is linked to ENSO and South China Sea warming. This study deepens our understanding of the varied impacts of El Niño on intraseasonal weather patterns in Indonesia, ultimately aiding in improving sub-seasonal-to-seasonal climate predictions over the IMC.