Global-scale interdecadal variability a skillful predictor at decadal-to-multidecadal timescales for Sahelian and Indian Monsoon Rainfall

In the present study, a sea surface temperature-based index named global-scale interdecadal variability (GIV) encompassing the combined variability of Atlantic multidecadal oscillation (AMO) and interdecadal Pacific oscillation (IPO) has been proposed. The warm phase of GIV exhibits a cold AMO-like pattern in the Atlantic basin and a warm IPO-like pattern in the Pacific basin. About 84% (R similar to-0.914) of Sahelian and 42% (R similar to-0.647) of Indian rainfall's temporal variance is attributed to GIV, showing substantial improvement compared to the variance explained by AMO and IPO individually. The physical mechanism for GIV-rainfall teleconnection is related to a modification of the Walker circulation. Although there is a substantial degree of uncertainty in the current generation of state-of-the-art climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), some still replicate the observed GIV's spatial structure, its teleconnection, and associated physical mechanism. The results presented herein advance our knowledge about rainfall's interdecadal variability and have imperative ramifications for developing skillful decadal predictions.

Automated summary

the present study proposes a sea surface temperature-based index called Global-scale Interdecadal Variability (GIV) that combines the variability of Atlantic Multidecadal Oscillation (AMO) and Interdecadal Pacific Oscillation (IPO). GIV is found to be significantly associated with rainfall changes in the Sahelian and Indian region, explaining a larger proportion of the variance compared to AMO and IPO individually. The mechanism behind this rainfall-GIV teleconnection is related to modifications in the Walker circulation. Some state-of-the-art climate models are able to reproduce the spatial structure and physical mechanism of observed GIV.