Accurate simulation of summertime convection associated with the Asian monsoon trough over the subtropical western Pacific is important but diffcult to achieve in many general circulation models (GCMs). This study reports a case in which bias could be reduced by introducing a higher-resolution regional atmospheric model (RAM), two-way nested in an atmospheric GCM over the western Pacific. Additional partial-coupling experiments revealed that GCM bias correction was insensitive to the coupling domain. The two-way nesting effect was similar to one phase of a leading mode of natural variability in the system. This is indicative that the two-way nesting model provides more realistic tropical heating that effectively excites a correct phase of the intrinsic dynamical mode to reduce GCM bias.