Forecasting tropical ENSO-induced drought conditions using sea surface height in the Western Pacific

The interannual variability of rainfall caused by the El Niño-Southern Oscillation (ENSO) results in significant changes in hydrologic conditions. Forecasting ENSO and its impacts are mainly based on Central Pacific Sea surface temperature (SST) anomalies which satisfactorily correlate with timing and, to a lesser extent, the intensity of drought conditions in the Philippines and the Western Pacific during the El Niño phase. Changes in sea surface height (SSH) are also brought upon by ENSO through seawater density changes with temperature and oceanographic processes. Here, we report that the associative nature of SSH and drought, as measured by surface runoff, has a better correlation (r > 0.693, p < 0.05) in terms of the expected timing (1 to 3 month lag) and intensity compared to using SST indices. Furthermore, since SSH is co-located with its corresponding forecasted decrease in runoff, a localised prediction can be made which further increases the accuracy of this predictive tool and can be used in tandem with SST-based ENSO indices. In the wake of a changing climate, the ability to forecast the timing and volume of rainfall and surface water availability is of utmost importance, especially within the context of food and water security.