Contact: marcy@ig.utexas.edu.
Speaker: Xian Wu, Assistant Professor, Department of Sustainable Earth Systems Sciences, University of Texas at Dallas
Host: Yuko Okumura
Title: Tropical Pacific decadal prediction: the role of volcanic forcing and ocean initialization
Abstract: Decadal climate predictions for the next 1 to 10 years provide critical information for climate adaptation and resilience planning, bridging the gap between well-established seasonal forecasts and centennial projections. As an initial condition–boundary condition problem, decadal predictions rely on both oceanic initial states and external radiative forcings. However, decadal prediction skill remains very low in the tropical Pacific, where ocean-atmosphere processes act as powerful drivers of global climate variations. Here, I will address whether this low prediction skill in the tropical Pacific arises from forecast system deficiencies or intrinsic limits of climate predictability. I will show that the tropical Pacific decadal prediction skill is unexpectedly degraded by the inclusion of historical volcanic aerosol forcing in the prediction system, due to poor model fidelity in simulating volcanic responses. In contrast, the no-volcano prediction system exhibits high skill, arising from the initial-condition memory associated with oceanic Rossby wave adjustment in the tropical Pacific. Furthermore, I will demonstrate the influence of other ocean basins on tropical Pacific decadal prediction through regional ocean initialization experiments. These findings improve our understanding of prediction system behavior in the tropical Pacific, which is crucial for advancing Earth system predictions.