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The effects of mixing on age of air

Garny, Hella and Birner, Thomas and Bönisch, Harald and Bunzel, Felix (2014) The effects of mixing on age of air. JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 119 (12), pp. 7015-7034. Wiley. DOI: 10.1002/2013JD021417 ISSN 2169-897X

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Official URL: http://onlinelibrary.wiley.com/doi/10.1002/2013JD021417/pdf

Abstract

Mean age of air (AoA) measures the mean transit time of air parcels along the Brewer-Dobson circulation (BDC) starting from their entry into the stratosphere. AoA is determined both by transport along the residual circulation and by two-way mass exchange (mixing). The relative roles of residual circulation transport and two-way mixing for AoA, and for projected AoA changes are not well understood. Here effects of mixing on AoA are quantified by contrasting AoA with the transit time of hypothetical transport solely by the residual circulation. Based on climate model simulations, we find additional aging by mixing throughout most of the lower stratosphere, except in the extratropical lowermost stratosphere where mixing reduces AoA. We use a simple Lagrangian model to reconstruct the distribution of AoA in the GCM and to illustrate the effects of mixing at different locations in the stratosphere. Predicted future reduction in AoA associated with an intensified BDC is equally due to faster transport along the residual circulation as well as reduced aging by mixing. A tropical leaky pipe model is used to derive a mixing efficiency, measured by the ratio of the two-way mixing mass flux and the net (residual) mass flux across the subtropical boundary. The mixing efficiency remains close to constant in a future climate, suggesting that the strength of two-way mixing is tightly coupled to the strength of the residual circulation in the lower stratosphere. This implies that mixing generally amplifies changes in AoA due to uniform changes in the residual circulation.

Item URL in elib:https://elib.dlr.de/90734/
Document Type:Article
Title:The effects of mixing on age of air
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Garny, HellaDLR, IPAUNSPECIFIED
Birner, ThomasColorado State University, Ft. Collins, USAUNSPECIFIED
Bönisch, HaraldInstitute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, DUNSPECIFIED
Bunzel, FelixMPI für Meteorologie, Hamburg, DUNSPECIFIED
Date:2014
Journal or Publication Title:JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:Yes
Volume:119
DOI :10.1002/2013JD021417
Page Range:pp. 7015-7034
Editors:
EditorsEmail
UNSPECIFIEDAmerican Geophysical Union
Publisher:Wiley
ISSN:2169-897X
Status:Published
Keywords:mixing, age of air, residual circulation
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Erdbeobachtung
DLR - Research theme (Project):R - Vorhaben Atmosphären- und Klimaforschung
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics
Deposited By: Ponater, Dr.rer.nat. Michael
Deposited On:25 Sep 2014 14:38
Last Modified:31 Jul 2019 19:48

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