Utilization of remote sensing data for mapping the effect of Indian Ocean Dipole (IOD) and El Nino Southern Oscillation (ENSO) in Sumatra Island

Abstract

IOD and ENSO are two global phenomena that are quite influencing the territory of Indonesia. Sumatra is one of the islands in Indonesia with unique local characteristics and is located in the westernmost. This study attempts to analyze how much the IOD and ENSO have affected rainfall in the Sumatra Island and which is more dominant, and the distribution that can be used as a reference in forecasting seasons and rainfall. In a period of 37 years (1981-2017), the influence of IOD and ENSO was analyzed using a correlation method which was then mapped. The rainfall data used was obtained from CHIRPS with a scale of 0.05. Data is processed using Climate Data Operator (CDO) and R-statistics to obtain correlation maps. Correlation calculations are carried out on the whole data and in the season period. The effect of IOD was seen to be significant in the southern part of Sumatra, with a maximum correlation of 0.4, while in the north and center, the correlation only -0.25. The effect of ENSO looks more evenly compared to the impact of IOD, with a correlation reaching -0.4 in the northern and southern parts of Sumatra. In contrast, the middle part shows a smaller correlation value with ranges of -0.1 to -0.3. In the DJF and MAM season periods, a positive correlation between rainfall and IOD occurred throughout Sumatra, and in the JJA and SON, a dominant-negative correlation occurred. In comparison, the ENSO shows dominant negative correlation in each period. Based on the correlation, ENSO is more influential on Sumatra compared to IOD in overall data. However, on seasonal data, IOD is more significant than ENSO. The southern part of Sumatra Island is the most affected by ENSO and IOD compared to other parts.