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Impact of Lagrangian transport on lower-stratospheric transport timescales in a climate model

Charlesworth, E. J. and Dugstad, A.-K. and Fritsch, Frauke and Jöckel, Patrick and Plöger, F. (2020) Impact of Lagrangian transport on lower-stratospheric transport timescales in a climate model. Atmospheric Chemistry and Physics (ACP), 20 (23), pp. 15227-15245. Copernicus Publications. doi: 10.5194/acp-20-15227-2020. ISSN 1680-7316.

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Official URL: https://acp.copernicus.org/articles/20/15227/2020/


We investigate the impact of model trace gas transport schemes on the representation of transport processes in the upper troposphere and lower stratosphere. Towards this end, the Chemical Lagrangian Model of the Stratosphere (CLaMS) was coupled to the ECHAM/MESSy Atmospheric Chemistry (EMAC) model and results from the two transport schemes (Lagrangian critical Lyapunov scheme and flux-form semi-Lagrangian, respectively) were compared. Advection in CLaMS was driven by the EMAC simulation winds, and thereby the only differences in transport between the two sets of results were caused by differences in the transport schemes. To analyze the timescales of large-scale transport, multiple tropical-surface-emitted tracer pulses were performed to calculate age of air spectra, while smaller-scale transport was analyzed via idealized, radioactively decaying tracers emitted in smaller regions (nine grid cells) within the stratosphere. The results show that stratospheric transport barriers are significantly stronger for Lagrangian EMAC-CLaMS transport due to reduced numerical diffusion. In particular, stronger tracer gradients emerge around the polar vortex, at the subtropical jets, and at the edge of the tropical pipe. Inside the polar vortex, the more diffusive EMAC flux-form semi-Lagrangian transport scheme results in a substantially higher amount of air with ages from 0 to 2 years (up to a factor of 5 higher). In the lowermost stratosphere, mean age of air is much smaller in EMAC, owing to stronger diffusive cross-tropopause transport. Conversely, EMAC-CLaMS shows a summertime lowermost stratosphere age inversion – a layer of older air residing below younger air (an “eave”). This pattern is caused by strong poleward transport above the subtropical jet and is entirely blurred by diffusive cross-tropopause transport in EMAC. Potential consequences from the choice of the transport scheme on chemistry–climate and geoengineering simulations are discussed.

Item URL in elib:https://elib.dlr.de/139350/
Document Type:Article
Title:Impact of Lagrangian transport on lower-stratospheric transport timescales in a climate model
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Charlesworth, E. J.Forschungszentrum Jülich, IEK-7 Stratosphäre, Jülich, Germanyhttps://orcid.org/0000-0002-1323-8881
Dugstad, A.-K.Forschungszentrum Jülich, IEK-7 Stratosphäre, Jülich, GermanyUNSPECIFIED
Fritsch, FraukeDLR, IPAhttps://orcid.org/0000-0001-6414-9726
Jöckel, PatrickDLR, IPAhttps://orcid.org/0000-0002-8964-1394
Plöger, F.Forschungszentrum Jülich, IEK-7 Stratosphäre, Jülich, GermanyUNSPECIFIED
Date:8 December 2020
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. 15227-15245
Publisher:Copernicus Publications
Keywords:Lagrangian Modelling, EMAC, MESSy, Modular Earth Submodel System, CLaMS, atmospheric transport, UTLS, age of air, age of air spectra
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Transport
HGF - Program Themes:Transport System
DLR - Research area:Transport
DLR - Program:V VS - Verkehrssystem
DLR - Research theme (Project):V - Transport und Klima
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Earth System Modelling
Deposited By: Jöckel, Dr. Patrick
Deposited On:09 Dec 2020 08:16
Last Modified:13 Jan 2021 16:09

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