CMIP5 model biases in the climatological mean state of the western Pacific warm pool

Biases in coupled general circulation models represent important limits for climate prediction. Based on historical runs of 26 coupled climate models of the Fifth Phase of the Coupled Model Intercomparison Project, the error of the climatological mean of the western Pacific warm pool (WPWP) is investigated. The results show that simulation of the morphology of the WPWP is significantly influenced by ocean currents. The upper-ocean heat budget analysis also indicates that heat advection plays a key role in determining the shape of the WPWP during the simulation. For the shrinkage of the tropical region and south section of smaller WPWPs, both the zonal heat advection bias caused by zonal ocean currents bias and meridional heat advection bias caused by the meridional sea temperature gradient bias are the crucial factors, while for the extension of larger WPWPs, the zonal heat advection bias is more important. For the northern section of WPWPs, the horizontal heat advection biases are still responsible for the shrinkage and extension in the region from 4°N to 7°N, while in the north of 7°N, the biases of WPWP are related to that of short wave radiation. In addition, in the equator and south section of the WPWP, the advective feedback plays a key role in the development of biases.