Impact of Atlantic and Pacific Decadal Sea Surface Temperature on precipitation extremes over the European and African continents

We quantify the impact of interdecadal sea surface temperature (SST) variability on precipitation extremes over continental Europe and central Africa using the OpenIFS atmospheric general circulation model. We performed 45-member ensemble experiments in which we removed SST anomalies obtained from linear regression with either the Interdecadal Pacific Variability (IPV) or the Atlantic Multidecadal Variability (AMV) from the daily SST in the Pacific Ocean and the Atlantic Ocean over the period 1950–2013. We also used coupled model simulations, particularly the Component C of the Decadal Climate Prediction Project (DCPP-C) as part of the Coupled Model Intercomparison Phase 6 (CMIP6). We find that precipitation extremes amplify over western and central Africa during the positive phase of AMV and reduce there during the negative phase of AMV. The positive phase of IPV reduces the precipitation extremes over western and central Africa and amplifies them during the negative phase. However, AMV and IPV do not show a significant impact over Europe except in some parts of Eastern Europe, where AMV causes more extreme precipitation during the positive phases and the IPV causes more over the Turkish region. Results from the atmosphere model are mostly consistent with the coupled model simulations from DCPP-C.

We also compute time of emergence for climate change signals over the period 1950-2013 and estimate that it takes approximately 700 years for a significant change in European precipitation extremes changes to emerge from the natural climate noise. The time of emergence reduces somewhat when AMV and IPV are removed, but is still on the order of centuries. The preliminary results of this study suggest that the potential importance of the internal variability of the Pacific and Atlantic Oceans is more crucial for the African continents than for the European regions.