The Ozone Hole Indirect Effect: Cloud-Radiative Anomalies Accompanying the Poleward Shift of the Eddy-Driven Jet in the Southern Hemisphere

Previous studies have shown that the development of the Antarctic ozone hole is linked to a poleward shift in the Southern Hemisphere (SH) mid-latitude jet, storm track, and precipitation patterns during summer months. This study provides the first attempt to quantify the changes in the clouds and the radiative budget of the SH associated with the poleward shift in the tropospheric circulation induced by the formation of the ozone hole. We perform single forcing climate model integrations using the Community Atmosphere Model, in which only stratospheric ozone depletion is specified. The results indicate that 1) high and mid-level clouds closely follow the poleward shift in the SH mid-latitude jet and that 2) low-level clouds decrease across most of the Southern Ocean. Similar cloud changes are found in International Satellite Cloud Climatology Project (ISCCP) observations during periods when the SH mid-latitude jet is anomalously poleward. The hemispherically averaged radiation anomaly associated with the cloud changes is calculated to be approximately +0.4 W m^-2, which arises largely from the reduction of the total cloud fraction at mid-latitudes. These dynamically induced cloud and radiation changes are therefore considerable and may play an important role in observed SH climate trends.