资源环境科技发展态势分析平台

Attribution of Antarctic ozone recovery to the Montreal protocol requires evidence that (1) Antarctic chlorine levels are declining and (2) there is a reduction in ozone depletion in response to a chlorine decline. We use Aura Microwave Limb Sounder measurements of O-3, HCl, and N2O to demonstrate that inorganic chlorine (Cl-y) from 2013 to 2016 was 223 +/- 93 parts per trillion lower in the Antarctic lower stratosphere than from 2004 to 2007 and that column ozone depletion declined in response. The mean Cl-y decline rate, similar to 0.8%/yr, agrees with the expected rate based on chlorofluorocarbon lifetimes. N2O measurements are crucial for identifying changes in stratospheric Cl-y loading independent of dynamical variability. From 2005 to 2016, the ozone depletion and Cl-y time series show matching periods of decline, stability, and increase. The observed sensitivity of O-3 depletion to changing Cl-y agrees with the sensitivity simulated by the Global Modeling Initiative chemistry transport model integrated with Modern Era Retrospective Analysis for Research and Applications 2 meteorology.

Plain Language Summary The Antarctic ozone hole is healing slowly because levels of the man-made chemicals causing the hole have long lifetimes. We use Microwave Limb Sounder (MLS) satellite data to measure O-3 over Antarctica at the beginning of winter and then compare it to O-3 near the end of winter to calculate depletion. During this period, nearly all O-3 change is due to depletion. MLS also measures HCl, and when ozone levels are very low, nearly all the reactive chlorine species (Cl-y) are converted to HCl. Cl-y varies a lot from year to year from atmospheric motions. Fortunately, MLS measures nitrous oxide (N2O), a long-lived gas that also varies with the motions. Using the ratio of Cl-y to N2O, we find that there is less chlorine now than 9 years ago and that Cl-y has decreased on average about 25 parts per trillion/yr (0.8%/yr). The O-3 depletion we calculate from MLS data responds to changes in the Cly levels, and the ratio of the change in ozone loss to the change in Cl-y matches model calculations. All of this is evidence that the Montreal Protocol is working-the Cl-y is decreasing in the Antarctic stratosphere and the ozone destruction is decreasing along with it.