Can Arctic Oscillation predict the southern Indian Ocean dipole at 8-month ahead?

Prediction of the southern Indian Ocean dipole (SIOD) used to rely on the tropical variabilities in previous studies, while the extratropical climate systems in the Northern Hemisphere may be unrepresented. This study finds the significant cross-seasonal influence of summertime Arctic Oscillation (AO) on the SIOD in the subsequent boreal spring. During positive AO phases, anomalous high sea level pressure is accompanied by the anticyclonic anomalies in the North Pacific y. As a response, the enhanced easterly wind anomalies along the tropical Pacific increase the local zonal gradient of sea surface temperature (SST) anomalies though the Walker circulation. Consequently, the surplus precipitation over the western Pacific sustains from boreal summer to fall, which sets the advantageous stage for SIOD initiation through exciting the cyclone (anticyclone) over the eastern (western) pole of the SIOD. The SIOD begins to grow in boreal winter in the context of the reinforcement of the heat fluxes and ocean processes, and finally peaks in the following spring. On this basis, an empirical model using the preceding summer AO to predict the subsequent spring SIOD is established. The correlation coefficient between the predicted and observed SIOD is 0.5, albeit slightly lower than that in the dynamical models from the North American multi-model ensemble project (0.53), whereas the prediction skills of the former are much higher than the latter in predicting individual SIOD events in terms of the hit rate and false alarm rate. This finding provides the new insight to improve the potential predictability of AO.