Observed temporal evolution of global mean age of stratospheric air for the 2002 to 2010 period

Stiller, G. P.; Clarmann, T. von; Haenel, Florian; Funke, B.; Glatthor, N.; Grabowski, U.; Kellmann, S.; Kiefer, Michael; Linden, A.; Lossow, Stefan; López‐Puertas, Manuel

doi:10.5194/acpd-11-28013-2011

Cited by 45 publications

(81 citation statements)

References 63 publications

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“…2). These results are in good agreement with previous estimations of the mean residence time of stratospheric air using sampling methods like aircrafts, high-altitude balloons and satellite observations 35,38,40 . Radioisotopes introduced in the atmosphere as a consequence of the nuclear bomb tests during the fifties and sixties are still useful tracers to study transport processes.…”

Section: Discussionsupporting

confidence: 92%

“…Our results show that significant fractions of radioactive aerosols (possibly small particles o0.1 mm) remain in the stratosphere for timescales of the order of several decades. Mean residence time of stratospheric air can be obtained from observations of tracer changes in the atmosphere [35][36][37][38][39][40][41] . We used an exponential distribution model (box model) to interpret the trend of Pu and 137 Cs in the stratosphere of Switzerland.…”

Section: Discussionmentioning

confidence: 99%

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Anthropogenic radionuclides in atmospheric air over Switzerland during the last few decades

et al. 2014

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The atmospheric nuclear testing in the 1950s and early 1960s and the burn-up of the SNAP-9A satellite led to large injections of radionuclides into the stratosphere. It is generally accepted that current levels of plutonium and caesium radionuclides in the stratosphere are negligible. Here we show that those radionuclides are present in the stratosphere at higher levels than in the troposphere. The lower content in the troposphere reveals that dry and wet deposition efficiently removes radionuclides within a period of a few weeks to months. Since the stratosphere is thermally stratified and separated from the troposphere by the tropopause, radioactive aerosols remain longer. We estimate a mean residence time for plutonium and caesium radionuclides in the stratosphere of 2.5-5 years. Our results also reveal that strong volcanic eruptions like Eyjafjallajökull in 2010 have an important role in redistributing anthropogenic radionuclides from the stratosphere to the troposphere.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Anthropogenic radionuclides in atmospheric air over Switzerland during the last few decades

et al. 2014

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“…Satellite-based measurements by the MIPAS instrument provide the only global observationally based data set of mean age trends hitherto [Stiller et al, 2012;Haenel et al, 2014]. Clearly, the measurement period of MIPAS (2002MIPAS ( -2012 is rather short, and respective AoA changes are likely affected by decadal variability.…”

Section: Age Of Air Simulation and Observationsmentioning

confidence: 99%

“…MIPAS AoA is deduced from observations of SF 6 , as described in much detail by Stiller et al [2008Stiller et al [ , 2012. The data version shown here is an improved data record of MIPAS age of air, derived from more recent version 5 spectral data with further improvements in the retrieval setup.…”

Section: Age Of Air Simulation and Observationsmentioning

confidence: 99%

Variability of stratospheric mean age of air and of the local effects of residual circulation and eddy mixing

et al. 2015

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We analyze the variability of mean age of air (AoA) and of the local effects of the stratospheric residual circulation and eddy mixing on AoA within the framework of the isentropic zonal mean continuity equation. AoA for the period 1988–2013 has been simulated with the Lagrangian chemistry transport model CLaMS driven by ERA‐Interim winds and diabatic heating rates. Model simulated AoA in the lower stratosphere shows good agreement with both in situ observations and satellite observations from Michelson Interferometer for Passive Atmospheric Sounding, even regarding interannual variability and changes during the last decade. The interannual variability throughout the lower stratosphere is largely affected by the quasi‐biennial‐oscillation‐induced circulation and mixing anomalies, with year‐to‐year AoA changes of about 0.5 years. The decadal 2002–2012 change shows decreasing AoA in the lowest stratosphere, below about 450 K. Above, AoA increases in the Northern Hemisphere and decreases in the Southern Hemisphere. Mixing appears to be crucial for understanding AoA variability, with local AoA changes resulting from a close balance between residual circulation and mixing effects. Locally, mixing increases AoA at low latitudes (40°S–40°N) and decreases AoA at higher latitudes. Strongest mixing occurs below about 500 K, consistent with the separation between shallow and deep circulation branches. The effect of mixing integrated along the air parcel path, however, significantly increases AoA globally, except in the polar lower stratosphere. Changes of local effects of residual circulation and mixing during the last decade are supportive of a strengthening shallow circulation branch in the lowest stratosphere and a southward shifting circulation pattern above.

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“…Confirming predict an acceleration of this global mass circulation of tropospheric air through the stratosphere. Stratospheric age of air and its temporal trend have been determined from SF 6 measurements from the MIPAS satellite (Stiller et al, 2012). Using a suite of stratospheric observations, Fu et al (2015) quantified the acceleration of the Brewer-Dobson circulation as 2.1% per decade for 1980-2009.…”

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confidence: 99%

Age of Air as a diagnostic for transport time-scales in global models

Krol¹,

Bruine²,

Killaars³

et al. 2017

Preprint

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Abstract. This paper presents the first results of an age of air (AoA) inter-comparison of six global transport models. Following a protocol, three global circulation models and three chemistry transport models simulated five tracers with boundary conditions that grow linearly in time. This allows for an evaluation of the AoA and transport times associated with inter-hemispheric transport, vertical mixing in the troposphere, transport to and in the stratosphere, and transport of air masses between land and ocean. Since AoA is not a directly measurable quantity in the atmosphere, simulations of 222 Rn and SF 6 were also requested. 5We focus this first analysis on averages over the period 2000-2010, taken from longer simulations covering the 1988 -2014 period. We find that two models, NIES and TOMCAT, show substantially slower vertical mixing in the troposphere compared to other models (LMDZ, TM5, EMAC, and ACTM). However, while the TOMCAT model, as used here, has slow transport between the hemispheres and between land and ocean, the NIES model shows efficient horizontal mixing and a smaller latitudinal gradient in SF 6 compared to the other models and observations. We find consistent differences between models concerning 10 vertical mixing of the troposphere, expressed as AoA differences and modeled 222Rn gradients between 950 and 500 hPa.All models agree, however, on an interesting asymmetry in inter-hemispheric mixing, with faster transport from the Northern hemisphere surface to the Southern hemisphere than vice versa. This is attributed to a rectifier caused by a stronger seasonal cycle in boundary layer venting over Northern hemispheric landmasses, and possibly to a related asymmetric position of the inter-tropical convergence zone. The calculated AoA in the upper stratosphere varies considerably among the models (4 -7 15 years). Finally, we find that the inter-model differences are generally larger than differences in AoA that result from using the same model with a different resolution or convective parameterisation. Taken together, the AoA model inter-comparison provides a useful addition to traditional approaches to evaluate transport time scales. Results highlight that inter-model differences 1 Geosci. Model Dev. Discuss., https://doi.org/10.5194/gmd-2017-262 Manuscript under review for journal Geosci. Model Dev. Discussion started: 7 November 2017 c Author(s) 2017. CC BY 4.0 License. associated with resolved transport (advection) and parameterised transport (convection, boundary layer mixing) are still large, and require further analysis. For this purpose, all model output and analysis software is available.

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Observed temporal evolution of global mean age of stratospheric air for the 2002 to 2010 period

Cited by 45 publications

References 63 publications

Anthropogenic radionuclides in atmospheric air over Switzerland during the last few decades

Anthropogenic radionuclides in atmospheric air over Switzerland during the last few decades

Variability of stratospheric mean age of air and of the local effects of residual circulation and eddy mixing

Age of Air as a diagnostic for transport time-scales in global models

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