\subsection{Surface temperature and heat flux}
The fact that the historical$-$AMIP CI bias, or equivalently the near surface moist static energy bias, agrees well with the rainfall bias raises the question of what controls the near surface moist static energy anomaly. \cite{Yang_2015} proposed that SSTs over the western Indian Ocean play an important role in modulating the East African rainfall annual cycle via controlling the near surface moist static energy of the air flowing onto the continent. We therefore examine if this mechanism can be applied to explain the rainfall difference between the historical run and the AMIP run. Fig. \ref{fig:TsMon} shows the historical$-$AMIP monthly climatology surface temperature (which is SST over the ocean) for the MRI-CGCM3. This is very similar to the spatial patterns of CI in Fig. \ref{fig:ciMon} or the moisture component of near surface moist static energy in Fig. \ref{fig:LvqMon} over the Indian Ocean. The SST bias has a pattern of cold north and warm south from January to May, with the coldest bias over the Arabian Sea. A pattern of warm west and cold east develops after May and maintains until October. This new pattern starts to decay from November and restores to the January--May north-south pattern in December. Therefore, the SST difference between the historical and AMIP run can largely explain the CI and the consequent rainfall biases over East Africa.