Drought Characteristics In Sumatra Based On Historical and Future Projection

Abstract

Drought represents a serious challenge for Sumatra, particularly in the context of climate change and further amplified by large-scale climate phenomena such as the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD). This study investigates drought characteristics using monthly ERA5 rainfall data (1981–2023) and bias-corrected CMIP6 projections (2015–2096). The analysis applies the Standardized Precipitation Index (SPI) at 3-, 6-, and 12-month scales, representing meteorological, agricultural, and hydrological droughts, respectively. Bias correction was performed using the Quantile Delta Mapping method on both historical and future datasets, accompanied by rainfall trend evaluation. The results reveal that droughts in Sumatra are spatially heterogeneous, with southern and lowland regions experiencing more frequent and prolonged meteorological droughts lasting up to five months. ENSO and IOD exhibits stronger influence in the southern hemisphere and lowland areas. When El Niño coincides with a positive IOD, this teleconnection delays monsoon onset, intensifies drought conditions for up to eight months, and accelerates the propagation of agricultural and hydrological droughts. However, not all meteorological droughts develop into agricultural or hydrological droughts; a persistence of 3–4 months is generally required before propagation occurs, with faster onset observed in southern and lowland regions. Future projections under the SSP5-8.5 scenario indicate a substantial increase in drought risk, with meteorological drought-affected areas expanding by about 40% (from 45% to 85%) and drought frequency increasing by up to 90%, particularly in southern Sumatra. In addition, rainfall trends show a shift toward drier conditions, especially during the dry season (JJA and SON). Under these conditions, intensified climate teleconnections are likely to further exacerbate drought risks and increase fire susceptibility in peat-rich lowlands. This study underscores the urgent need for region-specific adaptation strategies that account for topographic contrasts, hemispheric differences, and climate teleconnection influences to mitigate drought impacts and reduce fire hazards.