from CTL to EXP are the response to the mean state changes, rather than the cause of the deviation of the mean state. The anomalous eddy fluxes are shown in Figures 7cd, the pattern of which largely agrees with LH01. In the region of positive zonal wind anomalies (around 50$^\circ$), meridional temperature gradient increases at low levels (Figures 7ab), leading to enhanced baroclinic wave generation and stronger eddy heat flux (Figure 7d). Correspondingly, the equatorward propagation of waves enhances the poleward eddy momentum flux at around 45$^\circ$, which reinforces the zonal wind anomaly (Figure 7c). The strength of the eddy feedback can be calculated by projecting the anomalous eddy momentum flux convergence onto the anomalous zonal wind (see Baldwin et al. 2009 for details about projection of data with spatial weighting). The averaged feedback strength of the 10 ensemble simulations (referred to as $b_{LRF}$ hereafter) is around 0.137 day$^{-1}$, which is denoted by the red solid line in Figure 8. The red dashed lines in Figure 8 show the 95$\%$ confidence intervals of $b_{LRF}$, indicating little spread across the ensemble members. $b_{LRF}$ is considered as the ground truth in the idealized GCM.

![image](F04.pdf){width="\textwidth"}

![image](F05.pdf){width="\textwidth"}

The mean-state-independent eddy forcing is not 