Fig. \ref{fig:prMon} shows the historical\(-\)AMIP monthly climatology rainfall difference of MRI-CGCM3 over East Africa and surrounding areas. It is largely negative over East Africa from January to May and the absolute value is greatest in April, consistent with the multimodel mean result in Fig. \ref{fig:boxplotDif}. It is noted that the January–May negative values over East Africa are accompanied by a large scale pattern of dry north and wet south over the Indian Ocean, suggesting that the dry biases might be associated with large scale dynamics and the associated southward shifts of the ITCZ in the historical runs. Starting from June, a strong wet bias develops over the western Indian Ocean, abruptly shifting the biases over the Indian Ocean into a new pattern of wet west and dry east and keeping this new pattern until the end of the year. This large scale shift of the historical\(-\)AMIP precipitation difference has important impacts over East Africa, turning the previous negative precipitation biases into positive from June to November. The positive bias over East Africa peaks in September and October and turn slightly negative in December, consistent with the multimodel mean result in Fig. \ref{fig:boxplotDif}.