Analyzing the Role of the Madden–Julian Oscillation and Indian Ocean Dipole in Shaping Rainfall Patterns in West Sumatra

Abstract Weather and climate variability in Indonesia result from complex interactions between global, regional, and local phenomena. One of the phenomena affecting rainfall in Indonesia, particularly in West Sumatra Province, is the Madden Julian Oscillation (MJO) and the Dipole Mode (IOD). To improve the accuracy of daily weather prediction, an analysis of the relationship between weather and MJO and IOD phenomena in West Sumatra was conducted using the wavelet transform method. The study used daily rainfall data recorded by ARG, AWS, and Rain Post instruments distributed across 16 locations in West Sumatra, covering the observation period from 2015 to 2024. The results showed that the MJO influences rainfall in West Sumatra with oscillation periods of 31–50 days in the lowland and coastal areas of the western part of the region. The IOD affects rainfall in the hilly and eastern lowland areas, with longer oscillation periods of 53–66 days. During a negative IOD phase, the MJO increases the effectiveness of convective cloud formation, as observed from the Hovmöller diagram analysis. The correlation between OLR and IOD was found to be 0.54, while the correlation with MJO was negative, ranging from −0.18 to −0.28, indicating that local factors still predominantly influence.