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Observed Hemispheric Asymmetry in Stratospheric Transport Trends From 1994 to 2018
Author(s) -
Strahan Susan E.,
Smale Dan,
Douglass Anne R.,
Blumenstock Thomas,
Hannigan James W.,
Hase Frank,
Jones Nicholas B.,
Mahieu Emmanuel,
Notholt Justus,
Oman Luke D.,
Ortega Ivan,
Palm Mathias,
Prig Maxime,
Robinson John,
Schneider Matthias,
Sussmann Ralf,
Velazco Voltaire A.
Publication year - 2020
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 - 10.1029/2020gl088567
Subject(s) - stratosphere , northern hemisphere , atmospheric sciences , climatology , environmental science , southern hemisphere , extratropical cyclone , trace gas , ozone , atmospheric circulation , geology , meteorology , geography
Total columns of the trace gases nitric acid (HNO 3 ) and hydrogen chloride (HCl) are sensitive to variations in the lower stratospheric age of air, a quantity that describes transport time scales in the stratosphere. Analyses of HNO 3 and HCl columns from the Network for the Detection of Atmospheric Composition Change panning 77°S to 79°N have detected changes in the extratropical stratospheric transport circulation from 1994 to 2018. The HNO 3 and HCl analyses combined with the age of air from a simulation using the MERRA2 reanalysis show that the Southern Hemisphere lower stratosphere has become 1 month/decade younger relative to the Northern Hemisphere, largely driven by the Southern Hemisphere transport circulation. The analyses reveal multiyear anomalies with a 5‐ to 7‐year period driven by interactions between the circulation and the quasi‐biennial oscillation in tropical winds. This hitherto unrecognized variability is large relative to hemispheric transport trends and may bias ozone trend regressions.