CNN-Based ENSO Forecasts With a Focus on SSTA Zonal Pattern and Physical Interpretation

Abstract

Deep learning (DL) has achieved notable success in El Niño-Southern Oscillation (ENSO) forecasts. Most DL-based models focused on forecasting ENSO indices while the zonal distribution of sea surface temperature anomalies (SSTA) over the equatorial Pacific was overlooked. To provide accurate predictions for the SSTA zonal pattern, this study developed a model through leveraging the merits of the cosine distance in constructing the convolutional neural network. This model can skillfully predict the SSTA zonal pattern over the equatorial Pacific 1 year in advance, remarkably outperforming current dynamical models. Moreover, the physical interpretation of the model prediction reveals that the sources for ENSO predictability at different lead times are distinct. For the 10-month-lead predictions, the precursors in the north Pacific, south Pacific and tropical Atlantic play critical roles in determining the model behaviors; while for the 16-month-lead predictions, the initial signals in the tropical Pacific associated with the discharge-recharge cycle are essential.