The correlation is the statistical relationship between two variables. The correlation calculated is called the coefficient correlation. There are several statistical methods, depending on criteria. In an analysis of the bivariate correlation, we call the independent variables as predictor and also called dependent variable as criterion variable.
The indicators used to measure the anomaly of the ENSO such as Oceanic Nino Index (ONI), Multivariate ENSO Index (MEI), Japan Meteorological Agency Sea Surface Temperature Index (JMA SST Index), The Southern Oscillation Index (SOI), and Outgoing Long Wave Radiation (OLR) etc. The details are shown in Table 2.2.
In this study, the Oceanic Nino Index (ONI) is used indicators. The ONI is an index calculated from the sea surface temperature (SST). The ONI values are calculated from the Niño 3 area during the region 5°North to5°South ,150°West-90°West and the Niño 3.4 area during 5°N to 5°S, and 170°W to 120°W. The value of Nino is used to predict ENSO phenomenon and evaluate the strength of the spectacle.