In this study, we investigate the coupled model induced bias of the East African rainfall annual cycle common in CMIP3/5 that overestimates the short rains (OND) and underestimates the long rains (MAM), by comparing the historical (CMIP-style) and the corresponding AMIP (AMIP-style) runs for each model, with particular emphasis on the MRI-CGCM3. The framework of convective instability (CI) and moist static energy (MSE) link this bias to other tropical or global scale biases that have been found in previous studies \citep{Cai_2013,WangChunzai_2014}. The following conclusions have been reached: