The representation of the summer Southern African rainfall and its relationship with the Angolan Low and ENSO in the CORDEX models

Models tend to show strong rainfall biases over Southern Africa, especially during the Summer (DJF) months. This study aims to explore and understand why these biases occur. The Angolan Low (AL) and ENSO are two important sources of Summer rainfall variability. Thus, the study explores whether the relationship between the AL, ENSO and rainfall is represented correctly in three different ensembles; the CORDEX-CORE ensemble (CCORE, 0.22 degrees resolution), the lower resolution (0.44 degrees) CORDEX-phase 1 ensemble (C44) and the driving CMIP5 models. From regression analysis and a self organizing map the results show that wetter (drier) than normal DJF seasons usually occur during a strong (weak) AL and a La Nina (El Nino) event. While the models show this to an extent, they also show some differences in these relationships compared to the observed. The study examines some key dynamical features to understand why these differences occur. These results can further the understanding and improvement of the simulated Southern African rainfall in models.