RT Journal Article
T1 The influence of mixing on the stratospheric age of air changes in the 21st century
A1 Eichinger, Roland
A1 Dietmüller, Simone
A1 Garny, Hella
A1 Sacha , Petr
A1 Birner, Thomas
A1 Bönisch, Harald
A1 Pitari, Giovanni
A1 Visioni, Daniele
A1 Stenke, Andrea
A1 Rozanov, Eugene
A1 Revell, Laura
A1 Plummer, David A.
A1 Jöckel, Patrick
A1 Oman, Luke
A1 Deushi, Makoto
A1 Kinnison, Douglas E.
A1 Garcia, Rolando
A1 Morgenstern, Olaf
A1 Zeng, Guang
A1 Stone, Kane Adam
A1 Schofield, Robyn
K1 2502 Climatología
K1 2501 Ciencias de la Atmósfera
AB Climate models consistently predict an acceleration of theBrewer–Dobson circulation (BDC) due to climate change in the 21st century.However, the strength of this acceleration varies considerably amongindividual models, which constitutes a notable source of uncertainty forfuture climate projections. To shed more light upon the magnitude of thisuncertainty and on its causes, we analyse the stratospheric mean age of air(AoA) of 10 climate projection simulations from the Chemistry-Climate ModelInitiative phase 1 (CCMI-I), covering the period between 1960 and 2100. Inagreement with previous multi-model studies, we find a large model spread inthe magnitude of the AoA trend over the simulation period. Differencesbetween future and past AoA are found to be predominantly due to differencesin mixing (reduced aging by mixing and recirculation) rather than differencesin residual mean transport. We furthermore analyse the mixing efficiency, ameasure of the relative strength of mixing for given residual mean transport,which was previously hypothesised to be a model constant. Here, the mixingefficiency is found to vary not only across models, but also over time in allmodels. Changes in mixing efficiency are shown to be closely related tochanges in AoA and quantified to roughly contribute 10 % to the long-termAoA decrease over the 21st century. Additionally, mixing efficiencyvariations are shown to considerably enhance model spread in AoA changes. Tounderstand these mixing efficiency variations, we also present a consistentdynamical framework based on diffusive closure, which highlights the role ofbasic state potential vorticity gradients in controlling mixing efficiencyand therefore aging by mixing.
PB Atmospheric Chemistry and Physics
SN 16807324
YR 2019
FD 2019-01-24
LK http://hdl.handle.net/11093/4057
UL http://hdl.handle.net/11093/4057
LA eng
NO Atmospheric Chemistry and Physics, 19(2): 921-940 (2019)
NO Helmholtz Association | Ref. VH-NG-1014
DS Investigo
RD 08-oct-2024