  The linear response function (LRF) of an idealized GCM, the dry dynamical
core with Held-Suarez physics, is used to accurately compute how eddy momentum
and heat fluxes change in response to the zonal wind and temperature anomalies
of the annular mode at the low-frequency limit. Using these results and knowing
the parameterizations of surface friction and thermal radiation in Held-Suarez
physics, the contribution of each physical process (meridional and vertical
eddy fluxes, surface friction, thermal radiation, and meridional advection) to
the annular mode dynamics is quantified. Examining the quasi-geostrophic
potential vorticity balance, it is shown that the eddy feedback is positive and
increases the persistence of the annular mode by a factor of more than two.
Furthermore, how eddy fluxes change in response to only the barotropic
component of the annular mode, i.e., vertically averaged zonal wind (and no
temperature) anomaly, is also calculated similarly. The response of eddy fluxes
to the barotropic-only component of the annular mode is found to be drastically
different from the response to the full (barotropic+baroclinic) annular mode
anomaly. In the former, the barotropic governor effect significantly suppresses
the eddy generation leading to a negative eddy feedback that decreases the
persistence of the annular mode by nearly a factor of three. These results
suggest that the baroclinic component of the annular mode anomaly, i.e., the
increased low-level baroclinicity, is essential for the persistence of the
annular mode, consistent with the baroclinic mechanism but not the barotropic
mechanism proposed in the previous studies.
