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Quantifying the effect of mixing on the mean age of air in CCMVal-2 and CCMI-1 models

Dietmüller, Simone and Eichinger, Roland and Garny, Hella and Birner, Thomas and Boenisch, Harald and Pitari, Giovanni and Mancini, Eva and Visioni, Daniele and Stenke, Andrea and Revell, Laura and Rozanov, Eugene and Plummer, David A. and Scinocca, John and Jöckel, Patrick and Oman, Luke and Deushi, Makoto and Kiyotaka, Shibata and Kinnison, Douglas E. and Garcia, Rolando R. and Morgenstern, Olaf and Zeng, Guang and Stone, Kane Adam and Schofield, Robyn (2018) Quantifying the effect of mixing on the mean age of air in CCMVal-2 and CCMI-1 models. Atmospheric Chemistry and Physics (ACP), 18 (9), pp. 6699-6720. Copernicus Publications. doi: 10.5194/acp-18-6699-2018. ISSN 1680-7316.

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Official URL: https://www.atmos-chem-phys.net/18/6699/2018/


he stratospheric age of air (AoA) is a useful measure of the overall capabilities of a general circulation model (GCM) to simulate stratospheric transport. Previous studies have reported a large spread in the simulation of AoA by GCMs and coupled chemistry–climate models (CCMs). Compared to observational estimates, simulated AoA is mostly too low. Here we attempt to untangle the processes that lead to the AoA differences between the models and between models and observations. AoA is influenced by both mean transport by the residual circulation and two-way mixing; we quantify the effects of these processes using data from the CCM inter-comparison projects CCMVal-2 (Chemistry–Climate Model Validation Activity 2) and CCMI-1 (Chemistry–Climate Model Initiative, phase 1). Transport along the residual circulation is measured by the residual circulation transit time (RCTT). We interpret the difference between AoA and RCTT as additional aging by mixing. Aging by mixing thus includes mixing on both the resolved and subgrid scale. We find that the spread in AoA between the models is primarily caused by differences in the effects of mixing and only to some extent by differences in residual circulation strength. These effects are quantified by the mixing efficiency, a measure of the relative increase in AoA by mixing. The mixing efficiency varies strongly between the models from 0.24 to 1.02. We show that the mixing efficiency is not only controlled by horizontal mixing, but by vertical mixing and vertical diffusion as well. Possible causes for the differences in the models' mixing efficiencies are discussed. Differences in subgrid-scale mixing (including differences in advection schemes and model resolutions) likely contribute to the differences in mixing efficiency. However, differences in the relative contribution of resolved versus parameterized wave forcing do not appear to be related to differences in mixing efficiency or AoA.

Item URL in elib:https://elib.dlr.de/119969/
Document Type:Article
Title:Quantifying the effect of mixing on the mean age of air in CCMVal-2 and CCMI-1 models
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Birner, ThomasLMU MünchenUNSPECIFIED
Boenisch, HaraldKarlsruhe Institutee of Technology (KIT)UNSPECIFIED
Pitari, GiovanniUniv. l'Aquila, IUNSPECIFIED
Mancini, EvaUniv. L'Aquila, IUNSPECIFIED
Visioni, DanieleUniv. L'Aquila, IUNSPECIFIED
Stenke, AndreaETH Zürich, CHUNSPECIFIED
Revell, LauraBodeker Science, New ZealandUNSPECIFIED
Rozanov, EugenePhysikalisch-Meteorol. Observatorium Davos, CHUNSPECIFIED
Plummer, David A.Environment and Climate Change Canada, Climate resarch DivisionUNSPECIFIED
Scinocca, JohnEnvironment and Climate Change Canada, Climate resarch DivisionUNSPECIFIED
Jöckel, PatrickDLR, IPAhttps://orcid.org/0000-0002-8964-1394
Oman, LukeNASA Goddard Space Flight Center, Greenbelt, MD, USAUNSPECIFIED
Deushi, MakotoMeteorological Research Inst., Tsukuba, JUNSPECIFIED
Kiyotaka, ShibataSchool of Environmeantal Science and Enineering, JapanUNSPECIFIED
Kinnison, Douglas E.NCAR, Boulder, CO, USAUNSPECIFIED
Garcia, Rolando R.NCAR, Boulder, CO, USAUNSPECIFIED
Morgenstern, OlafNational Inst. of Water and Atmos. Research, Lauder, NZUNSPECIFIED
Zeng, GuangNational Institute of Water and Atmospheric Research, Lauder, New ZealandUNSPECIFIED
Stone, Kane AdamSchool of Earth science, University of MelbourneUNSPECIFIED
Schofield, RobynARC Centre of Excellence for Climate System Science, SydneyUNSPECIFIED
Date:14 May 2018
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
DOI :10.5194/acp-18-6699-2018
Page Range:pp. 6699-6720
EditorsEmailEditor's ORCID iD
Publisher:Copernicus Publications
Keywords:stratospheric transport, age of air, model inter-comparison
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
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Earth System Modelling
Deposited By: Dietmüller, Simone
Deposited On:22 May 2018 09:33
Last Modified:02 May 2019 13:59

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