HR: 10:50h
AN: A32C-02    [Abstracts]
TI: Ensemble simulations of the decline and recovery of polar ozone
AU: * Wilson, R J
EM: john.wilson@noaa.gov
AF: Geophysical Fluid Dynamics Lab., PO Box 308, Princeton, NJ 08540 United States
AU: Austin, J
EM: john.austin@noaa.gov
AF: Geophysical Fluid Dynamics Lab., PO Box 308, Princeton, NJ 08540 United States
AB: An ensemble of simulations of a coupled chemistry-climate model is completed for the period 1960 to 2100. The simulations are divided into two periods, 1960-2005 and 1990-2100. For the past, the model is forced with observed sea surface temperatures, the observed concentrations of chlorofluorocarbons and greenhouse gases, observed aerosol amounts and the observed solar cycle. For the future, the model is forced with the sea surface temperatures taken from a coupled atmosphere-ocean climate simulation for the same model, while the other forcings are taken from a variety of sources. The 15-year overlap between the `past' runs and the `future' runs allowed the results to be tested for the sensitivity to the forcing data. The Antarctic ozone hole developed rapidly in the model from about the late 1970s and the minimum ozone agrees well with observations, albeit with a slight low bias. The ozone hole area is smaller than observed and scales approximately linearly with minimum ozone. Absolute Minimum ozone is attained during the period 2000-2015, but the ozone hole disappears somewhat more slowly than it initially took to form. The ozone hole does not generally dissappear until about 2065, almost two decades later than current expectations. However, depending on the precise definition chosen, and depending on interannual variability and ensemble member, some results as early as 2050 may be devoid of the Antarctic ozone hole, while other results beyond 2075 may have a small ozone hole. In contrast the Arctic recovered to 1980 conditions by about 2040, but with an even larger range of possible dates. No equivalent of the Antarctic ozone hole was simulated in the Arctic. Allowing for model bias, the minimum ozone was about 200 DU, with bias-corrected values below 225DU attained during the period 1995-2020. The depth of the Antarctic ozone hole is driven primarily by changes in halogen amounts, whereas in the Arctic halogen amounts, although important, have a weaker impact. The results suggest that the difference in timing in ozone recovery is due to the differing impact of climate change for the two polar regions.
UR: http://www.gfdl.noaa.gov/~jaa/Results2.html
DE: 0340 Middle atmosphere: composition and chemistry
DE: 0341 Middle atmosphere: constituent transport and chemistry (3334)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005