Influences El Nino Southern Oscillation (ENSO) on Rainfall in East Kalimantan-Indonesia

Abstract

The El Nino Southern Oscillation (ENSO) is a global hydro-climate phenomenon that affects temperature [1] rainfall [2], discharge, and evaporation. The aims of the study are to examine influences ENSO on rainfall in East Kalimantan, Indonesia. This research uses Southern Oscillation Index (SOI) as ENSO parameters. The data set starts from 1986 to 2012 and consist of 24 rainfall stations. The correlation analysis uses Pearson Product-Moment Correlation. Correlation was calculated by dividing it into 4 seasons: January-February-March (JFM), April-May-June (AMJ), July-August-September (JAS), and October-November-December (OND). Testing were conducted from lag-0 to lag-3. The highest correlations were identified in seasons JAS and OND in lag 0, almost all of the stations indicated positive correlations with r greater than 0.3. These showed that the high correlation between ENSO and rainfall occurred in July to December during lag 0. In lag 1, several stations still have a positive correlation. Some stations maintained a correlation coefficient almost identical to the lag 0. The correlation was lower in lag 2 and lag 3. These lags generally have a negative correlation with r -0.3 to 0 (weak correlation). From the results, we could conclude that ENSO events have a direct impact on rainfall in East Kalimantan, Indonesia. The highest influence occurred in JAS and OND with moderate correlation strength. Rainfall was decreasing in El Nino event and increasing in La Nina event. The result also indicate that ENSO still have impact in three, six, and nine months lag time on rainfall. However, it had just a weak effect.