THE CAUSALITY RELATIONSHIP OF EL NIÑO SOUTHERN OSCILLATION (ENSO) AND INDIAN OCEAN DIPOLE (IOD) ON METEOROLOGICAL DROUGHT IN BALI

Drought is a slow-onset disaster with far-reaching impacts. Drought often begins with a deficiency in precipitation, which is called meteorological drought, caused by fluctuations in atmospheric responses to the biosphere. El Niño, a temperature anomaly in the Pacific Ocean, leads to longer dry season in Indonesia, particularly the eastern region. Meanwhile, temperature anomalies in the Indian Ocean, known as positive Indian Ocean Dipole (IOD), induce dry condition in western Indonesia. This study aims to evaluate the influence of the El Nino phenomenon and positive IOD on drought occurrences in Bali, a region situated in the middle part of Indonesia. Monthly precipitation data is collected from a total of 43 rain stations throughout Bali. The Standardized Precipitation Index (SPI-3) on a 3-month time scale is used to quantify dryness level. SPI-3 is linked to the Ocean Niño Index (ONI) and Dipole Mode Index (DMI) using Pearson's correlation coefficient and Linear Granger causality test. The findings of this study show that the correlation between SPI and ONI is stronger than the correlation between SPI and DMI. The drought resulting from the concurrent occurrence of El Niño and Positive IOD was more severe compared to drought caused solely by El Niño. Both El Niño and Positive IOD did happened together in 1997 and 2006-2007 caused the SPI3 value more negative than 2015 and 2019 which El Niño and Positive IOD happened solely respectively.