Modulation of ETCCDI-based extreme rainfall indices by ENSO and the Indian Ocean Dipole over topographically complex North Sumatra, Indonesia
DOI: https://doi.org/10.3846/gac.2026.26129Abstract
This study examines the characteristics of extreme rainfall in North Sumatra Province, Indonesia, and its teleconnections with the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). The analysis uses a blended daily rainfall dataset from 1990 to 2024, combining station observations from the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG) with the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) satellite data. Validation of CHIRPS against 61 station records shows strong reliability, with an average Pearson correlation (r) of 0.83 and a Root Mean Square Error (RMSE) of 53.1 mm over 20 years. Analysis of extreme rainfall indices from the Expert Team on Climate Change Detection and Indices (ETCCDI) reveals a significant influence from global climate phenomena. The La Niña phase of ENSO and the negative phase of the IOD are consistently associated with wetter conditions, characterized by higher annual rainfall totals (PRCPTOT), increased maximum 1-day (RX1day) and 5-day (RX5day) precipitation, and longer Consecutive Wet Days (CWD). Conversely, the El Niño and positive IOD phases lead to drier conditions and an increased risk of meteorological drought, as evidenced by significantly higher counts of Consecutive Dry Days (CDD). Notably, a sharp decline in extreme-frequency events observed since 2020 contradicts typical La Niña patterns, suggesting a shift in teleconnections. Spatially, the highest rainfall intensity and duration are concentrated in the western and southern coastal and mountainous regions, while the northeastern lowlands are comparatively drier. These findings underscore the strong modulation of regional hydro-climatic extremes by large-scale climate drivers and provide a quantitative basis for enhancing climate change adaptation and disaster mitigation strategies in one of Indonesia’s most vulnerable provinces.
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extreme rainfall, CHIRPS, hazard, El Niño, climate, weatherHow to Cite
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