Uncertainty and resolution dependence of the atmospheric response to decadal variability of the Kuroshio Extension
The both reanalysis and AGCM simulations show that the response of lower-tropospheric meridional heat flux due to sub-weekly eddies (as a measure of storm track activity) to the decadal variability of KE’s dynamical state is characterized by a northward (southward) shift of the storm track when the KE is stable (unstable). While ensemble-averaged response in the AGCM simulations agrees well with the response detected in the reanalysis, a large spread exists in the response across ensemble members: there is large uncertainty due to atmospheric internal variability in the observational estimate of the atmospheric circulation response to extra-tropical SST anomalies. For the ensemble-averaged response in lower-tropospheric storm track activity, our simulations do not show much difference between 50km and 100km resolutions. We further identify the leading mode of the forced variability of near-surface baroclinicity in the KE region with SVD analysis between the reanalysis and ensemble model simulations. The leading mode is characterized by the strengthening/weakening of the baroclinicity over the KE region, which is nonetheless under the strong influence of remote tropical variability and is not enhanced in the higher-resolution AGCM. Meanwhile, a benefit of the higher resolution is hinted in local vertical motion response to the KE’s dynamical state.