directly observable and cannot be separated from the mean-state-dependent eddy forcing in the reanalysis data, but can be computed in the idealized GCM as $\tilde{M} = M - b_{LRF}Z$. The power spectrum of the mean-state-independent eddy forcing is shown in Figure 9. At timescales shorter than around 50 days, the mean-state-independent eddy forcing dominates the total eddy forcing. In particular, it is confirmed that the mean-state-independent eddy forcing is responsible for the broad peak of total eddy forcing at synoptic timescales. At timescales longer than 50 days, the strength of the mean-state-independent eddy forcing decreases with decreasing frequency, while the strength of the total eddy forcing rises as frequency decreases.

![image](F06.pdf){width="22pc"}

[At intraseasonal to interannual timescales, the total eddy forcing is dominated by mean-state-dependent eddy forcing. Here, the role of the medium-scale waves, whose period is shorter than 2 days, in the annular mode dynamics is emphasized. It has been shown that the amplitude of the medium-scale waves, which is weak in the climatology, is strongly modified by the annular mode, and the fluxes resulting from these waves have a substantial contribution to the annular mode dynamics]{} [@Kuroda2011]. At interannual timescales, the total eddy forcing calculated from daily wind anomalies 