Multiple regression and Artificial Neural Network for long-term rainfall forecasting using large scale climate modes

In this study, the application of Artificial Neural Networks (ANN) and Multiple Regression analysis (MR) to forecast long-term seasonal spring rainfall in Victoria, Australia was investigated using lagged El Nino Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) as potential predictors. The use of dual (combined lagged ENSO-IOD) input sets for calibrating and validating ANN and MR Models is proposed to investigate the simultaneous effect of past values of these two major climate modes on long-term spring rainfall prediction. The MR models that did not violate the limits of statistical significance and multicollinearity were selected for future spring rainfall forecast. The ANN was developed in the form of multilayer perceptron using Levenberg-Marquardt algorithm. Both MR and ANN modelling were assessed statistically using mean square error (MSE), mean absolute error (MAE), Pearson correlation (r) and Willmott index of agreement (d).The developed MR and ANN models were tested on out-of-sample test sets; the MR models showed very poor generalization ability for east Victoria with correlation coefficients of -0.99~ -0.90 compared to ANN with correlation coefficients of 0.42~0.93; ANN models also showed better generalization ability for central and west Victoria with correlation coefficients of 0.68~0.85 and 0.58~0.97 respectively. The ability of multiple regression models to forecast out-of-sample sets is compatible with ANN for Daylesford in central Victoria and Kaniva in west Victoria (r=0.92 and 0.67 respectively). The errors of the testing sets for ANN models are generally lower compared to multiple regression models. The statistical analysis suggest the potential of ANN over MR models for rainfall forecasting using large scale climate modes.