eddy forcing. The role of the medium-scale waves on the annular mode is emphasized in the present study, which shows that less than half of the total eddy forcing can be captured using daily wind anomalies at interannual timescales as reported before in Kuroda and Mukougawa (2011). Without accounting for the medium-scales waves, the eddy feedback strength is underestimated by around 40$\%$.]{}

The present study focuses on an equinoctial mean state in the idealized GCM. While a number of previous studies [e.g., @Barnes2010; @Byrne2016; @Sheshadri2016] have brought attention to the seasonality of the annular mode. Seasonal variations of the persistence of the annular mode and eddy-jet feedback will be explored using the present methodology in a future study.

The statistical methods proposed by LH01 and S13 are evaluated against the result from the LRF. By fitting the cross-correlations between the zonal index and eddy forcing as in LH01, the estimated feedback strength is fairly close to the result from the LRF, but it is difficult to determine *a priori* an optimal value of decorrelation timescales, a parameter needed to calculate the best-fit. Following S13, the output from lag-regression varies with lag days, and the feedback strength is largely underestimated, which 