Evaluation of the Co-Behavior of Regional Climate Drivers in the CMIP5 Ensemble Over Southern Africa

The study uses co-behavior analysis to examine the combinatory influence of large-scale processes over southern African climate. The evaluation of Global Climate Model (GCM) representation of the influence of multiple process interactions on regional climates is fundamental to assessing GCM performance. Such evaluations are used qualitatively to assess the plausibility of future climate projections for a particular region, as well as quantitatively in model selections or ensemble weighting approaches. While many studies have evaluated models based on their representation of the mean state of the climate, and with respect to societally relevant surface variables, evaluation of model representations of key physical processes underlying these surface responses are lacking. A process-based evaluation arguably provides a more holistic approach to examine the mechanisms driving regional climate responses. The ability of models to represent co-behavior of key processes may improve confidence in future projections and thereby assist in climate change adaptation planning. In this study, we apply a previously developed methodology for examining the interacting influence of large-scale atmospheric processes (co-behavior) to evaluate GCM historical simulations representations of key southern African regional climate processes and co-behavior. The evaluated GCMs represent similarly the co-behavior of El Niño Southern Oscillation (ENSO) and Antarctic Oscillation (AAO) large-scale processes with regional circulation processes. However, the GCMs show large variability when compared to the reanalysis in representing the variability and co-behaviour of the Inter-tropical Convergence Zone (ITCZ). The results confirm and build on previous work as well as providing further insights into the co-behavior framing and analysis approach. Again this understanding will be useful for decision- and policy makers in adapting to a changing climate.