Troposphere response to SST anomalies in the Antarctic Circumpolar Wave in the Southern Ocean

We diagnose potential temperature and vorticity budgets in the troposphere associated with the Antarctic circumpolar wave (ACW) along its path around the Southern Ocean utilizing National Centers for Climate Prediction (NCEP) sea surface temperature (SST), sea level pressure (SLP), troposphere air temperature (AT) and wind, air-sea heat flux (Q), and precipitation (PCP) anomalies from 1982 to 1999. We find warm SST anomalies during autumn/winter associated with outgoing air-sea latent heat flux (QE), wet PCP, and warm AT anomalies following the ACW across the Indian and western and central Pacific sectors of the Southern Ocean, indicating that SST anomalies drive anomalous mid-level diabatic heating there. In this region the path of the ACW coincides with that of autumn/winter cyclogenesis (Simmonds and Keay, 2000), along which warm SST anomalies are aligned with low-level convergence and upper-level divergence anomalies, both yielding anomalous mid-level ascent. Thus, diagnosis of the potential temperature budget finds anomalous SST-induced mid-level diabatic heating balanced principally by anomalous vertical heat advection. Diagnosing the potential vorticity budget, anomalous low level convergence is balanced by anomalous meridional advection of planetary vorticity while upper-level divergence is balanced by westward advection of anomalous relative vorticity, together yielding vertical coherence in the baroclinic wind response to SST-induced mid-level diabatic heating. This contrasts with the ACW in the eastern Pacific and Atlantic sectors of the Southern Ocean, the path lying south of the zone of autumn-winter cyclogenesis, where the anomalous SST tendency is driven by equivalent barotropic structures in the troposphere induced by meridional atmospheric teleconnections associated with the El Nino-Southern Oscillation.