A Comparative study of the effects of the Indian ocean dipole and the El Niño in 2019 and 2023 on agricultural drought in Karawang Regency, Indonesia

Abstract

This study examines the effects of El Niño and the Indian Ocean Dipole (IOD) in 2019 and 2023 on drought conditions in rice fields in Karawang Regency. Both IOD and El Niño influence agricultural drought indirectly through meteorological drought. The IOD in 2019 was classified as extreme, while the El Niño in 2023 was considered strong. The Oceanic Niño Index (ONI) and Dipole Mode Index served as indicators for El Niño and IOD. Meteorological drought was evaluated using the Standardized Precipitation Index (SPI), while agricultural drought was measured with the Normalized Difference Drought Index (NDDI). The results revealed that the most severe meteorological droughts in both years occurred in August and September, with the 2023 drought being more widespread due to elevated IOD and ONI indices. There was a two-month delay between these droughts and the related IOD and El Niño events. Agricultural drought showed significant variation between 2019 and 2023, with 2019 experiencing an earlier and more extensive drought in the northern and central regions, while 2023 saw a later and more intense drought in specific locations. This agricultural drought lagged behind the meteorological drought by about two (three) months in 2019 (2023), likely due to differences in soil water retention, peaking in October of both years after a decline in July of 2019 (August in 2023) influenced by reservoir-fed irrigation.