Transport, Radiative, and Dynamical Effects of the Antarctic Ozone Hole: A GFDL “SKYHI” Model Experiment

Abstract

The GFDL “SKYHI” general circulation model has been used to simulate the effect of the Antarctic “ozone hole” phenomenon on the radiative and dynamical environment of the lower stratosphere. Both the polar ozone destruction and photochemical restoration chemistries are calculated by parameterized simplifications of the still somewhat uncertain chemical processes. The modeled total column ozone depletions are near 25% in spring over Antarctica, with 1% depletion reaching equatorial latitudes by the end of the 4½–year model experiment. In the lower stratosphere, ozone reductions of 5% reach to the equator. Large coolings of about 8 K are simulated in the lower stratosphere over Antarctica in late spring, while a general cooling of about 1–1.5 K is present throughout the Southern Hemisphere lower stratosphere. The model atmosphere experiences a long-term positive temperature-chemical feedback because significant ozone reductions carry over into the next winter. The overall temperature response to the reduced ozone is essentially radiative in character. However, substantial dynamical changes are induced by the ozone hole effect. The Antarctic middle stratosphere in late spring warms by about 6 K over Antarctica and the lower midlatitude stratosphere warms by approximately 1 K. These warming spots are produced mainly by an increased residual circulation intensity. Also, the Antarctic vortex becomes tighter and more confined as a result of the reduced ozone. These two dynamical effects combine to steepen the meridional slope of quasi-conservative trace constituent isolines. Thus, the entire transport, radiative, and dynamical climatology of the springtime stratosphere is affected to an important degree by the ozone hole phenomenon. Over the entire year, however, these dynamical effects are considerably smaller.