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Extratropical age of air trends and causative factors in climate projection simulations

Sácha, Petr and Eichinger, Roland and Garny, Hella and Pisoft, Petr and Dietmüller, Simone and de la Torre, Laura and Plummer, David and Jöckel, Patrick and Morgenstern, Olaf and Zeng, Guang and Butchart, Neil and Añel, Juan A. (2019) Extratropical age of air trends and causative factors in climate projection simulations. Atmospheric Chemistry and Physics (ACP), 19 (11), pp. 7627-7647. Copernicus Publications. doi: 10.5194/acp-19-7627-2019. ISSN 1680-7316.

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Official URL: https://www.atmos-chem-phys.net/19/7627/2019/


Climate model simulations show an acceleration of the Brewer–Dobson circulation (BDC) in response to climate change. While the general mechanisms for the BDC strengthening are widely understood, there are still open questions concerning the influence of the details of the wave driving. Mean age of stratospheric air (AoA) is a useful transport diagnostic for assessing changes in the BDC. Analyzing AoA from a subset of Chemistry–Climate Model Initiative part 1 climate projection simulations, we find a remarkable agreement between most of the models in simulating the largest negative AoA trends in the extratropical lower to middle stratosphere of both hemispheres (approximately between 20 and 25 geopotential kilometers (gpkm) and 20–50∘ N and S). We show that the occurrence of AoA trend minima in those regions is directly related to the climatological AoA distribution, which is sensitive to an upward shift of the circulation in response to climate change. Also other factors like a reduction of aging by mixing (AbM) and residual circulation transit times (RCTTs) contribute to the AoA distribution changes by widening the AoA isolines. Furthermore, we analyze the time evolution of AbM and RCTT trends in the extratropics and examine the connection to possible drivers focusing on local residual circulation strength, net tropical upwelling and wave driving. However, after the correction for a vertical shift of pressure levels, we find only seasonally significant trends of residual circulation strength and zonal mean wave forcing (resolved and unresolved) without a clear relation between the trends of the analyzed quantities. This indicates that additional causative factors may influence the AoA, RCTT and AbM trends. In this study, we postulate that the shrinkage of the stratosphere has the potential to influence the RCTT and AbM trends and thereby cause additional AoA changes over time.

Item URL in elib:https://elib.dlr.de/127825/
Document Type:Article
Title:Extratropical age of air trends and causative factors in climate projection simulations
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Sácha, PetrUniv. Prag, Tschechische RepublikUNSPECIFIED
Eichinger, RolandMIM, Univ. München und DLR, IPAUNSPECIFIED
Garny, HellaDLR, IPA und MIM, Univ. MünchenUNSPECIFIED
Pisoft, PetrUniv. Prag, Tschechische RepublikUNSPECIFIED
de la Torre, LauraUniv. de Vigo, Ourense, SpanienUNSPECIFIED
Plummer, DavidEnviron. Canada, Victoria, BC, KanadaUNSPECIFIED
Jöckel, PatrickDLR, IPAhttps://orcid.org/0000-0002-8964-1394
Morgenstern, OlafNIWA, Lauder, NeuseelandUNSPECIFIED
Zeng, GuangNIWA, Lauder, NeuseelandUNSPECIFIED
Butchart, NeilMet Office, Exeter, UKUNSPECIFIED
Añel, Juan A.Universidade de Vigo, Ourense, SpanienUNSPECIFIED
Journal or Publication Title:Atmospheric Chemistry and Physics (ACP)
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:Yes
Page Range:pp. 7627-7647
EditorsEmailEditor's ORCID iD
Publisher:Copernicus Publications
Series Name:Copernicus
Keywords:climate models, age of air, trends, stratosphere, upward shift
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Earth Observation
DLR - Research theme (Project):R - Atmospheric and climate research, R - Project Climatic relevance of atmospheric tracer gases, aerosols and clouds
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Earth System Modelling
Deposited By: Eichinger, Roland
Deposited On:17 Jun 2019 13:39
Last Modified:17 Jun 2019 13:39

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