Asymmetric response of the atmosphere to SST anomalies associated with Kuroshio Extension decadal variability

Abstract

Abstract Using regional climate Model version 4.6, two sets of numerical experiments were designed to investigate the response of atmospheric circulation to symmetric sea surface temperature anomalies (SSTAs) associated with the decadal variability in the Kuroshio Extension (KE) under different atmospheric backgrounds in winter. The results show that the response of the atmosphere to symmetric SSTAs exhibits an asymmetric baroclinic structure related to the stable state of the KE and an equivalent barotropic structure related to the unstable state of the KE under the background of climatology. The diabatic heating associated with cumulus convection and barotropic processes, including irreversible potential vorticity mixing and wave breaking, exerts evident atmospheric circulation and is the main reason for the formation of the asymmetric atmospheric circulation structure. While using a given atmospheric field background in 2008 instead of the climatological background, the response of the atmosphere to SSTAs related to the KE unstable state is similar to the response of the atmosphere to SSTAs related to the KE stable state. The response pattern primarily results from the barotropic processes of nonlinear wave breaking, not the SSTAs coming from the internal variability of the atmosphere at midlatitudes.