On the hiatus in the acceleration of tropical upwelling since the beginning of the 21st century

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dc.contributor.authorAschmann, J.
dc.contributor.authorBurrows, J. P.
dc.contributor.authorGebhardt, C.
dc.contributor.authorRozanov, A.
dc.contributor.authorHommel, R.
dc.contributor.authorWeber, M.
dc.contributor.authorThompson, Anne M.
dc.date.accessioned2024-06-20T17:32:14Z
dc.date.available2024-06-20T17:32:14Z
dc.date.issued2014-12-05
dc.description.abstractChemistry–climate models predict an acceleration of the upwelling branch of the Brewer–Dobson circulation as a consequence of increasing global surface temperatures, resulting from elevated levels of atmospheric greenhouse gases. The observed decrease of ozone in the tropical lower stratosphere during the last decades of the 20th century is consistent with the anticipated acceleration of upwelling. However, more recent satellite observations of ozone reveal that this decrease has unexpectedly stopped in the first decade of the 21st century, challenging the implicit assumption of a continuous acceleration of tropical upwelling. In this study we use three decades of chemistry-transport-model simulations (1980–2013) to investigate this phenomenon and resolve this apparent contradiction. Aside from a high-bias between 1985–1990, our model is able to reproduce the observed tropical lower stratosphere ozone record. A regression analysis identifies a significant decrease in the early period followed by a statistically robust trend-change after 2002, in qualitative agreement with the observations. We demonstrate that this trend-change is correlated with structural changes in the vertical transport, represented in the model by diabatic heating rates taken from the reanalysis product Era-Interim. These changes lead to a hiatus in the acceleration of tropical upwelling between 70–30 hPa and a southward shift of the tropical pipe at 30 and 100 hPa during the past decade, which appear to be the primary causes for the observed trend-change in ozone.
dc.description.sponsorshipThis study has been funded in part by the University and State of Bremen, the DFG Research Unit 1095 Stratospheric Change and its Role for Climate Prediction, SHARP, and the German Federal Ministry of Education and Research, research project Role Of the Middle atmosphere In Climate (ROMIC). SHADOZ, the Southern Hemisphere Additional Ozonesondes network, is funded by NASA’s Upper Atmosphere Research Program. We thank G. Stiller and the three anonymous referees for their help in improving the manuscript.
dc.description.urihttps://acp.copernicus.org/articles/14/12803/2014/
dc.format.extent12 pages
dc.genrejournal articles
dc.identifierdoi:10.13016/m2pfaf-jrit
dc.identifier.citationAschmann, J., J. P. Burrows, C. Gebhardt, A. Rozanov, R. Hommel, M. Weber, and A. M. Thompson. “On the Hiatus in the Acceleration of Tropical Upwelling since the Beginning of the 21st Century.” Atmospheric Chemistry and Physics 14, no. 23 (December 5, 2014): 12803–14. https://doi.org/10.5194/acp-14-12803-2014.
dc.identifier.urihttps://doi.org/10.5194/acp-14-12803-2014
dc.identifier.urihttp://hdl.handle.net/11603/34749
dc.language.isoen_US
dc.publisherEGU
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Faculty Collection
dc.relation.ispartofUMBC GESTAR II
dc.rightsThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
dc.rightsPublic Domain
dc.rights.urihttps://creativecommons.org/publicdomain/mark/1.0/
dc.titleOn the hiatus in the acceleration of tropical upwelling since the beginning of the 21st century
dc.typeText
dcterms.creatorhttps://orcid.org/0000-0002-7829-0920

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