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Decline in Antarctic Ozone Depletion and Lower Stratospheric Chlorine Determined From Aura Microwave Limb Sounder Observations
Author(s) -
Strahan Susan E.,
Douglass Anne R.
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl074830
Subject(s) - microwave limb sounder , ozone depletion , stratosphere , ozone , atmospheric sciences , ozone layer , chlorine , environmental science , chlorofluorocarbon , climatology , chemistry , meteorology , geology , physics , organic chemistry
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 N 2 O 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, ~0.8%/yr, agrees with the expected rate based on chlorofluorocarbon lifetimes. N 2 O 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.