On the relationship between the strength of the Brewer‐Dobson circulation and the age of stratospheric air

Austin, J.; Li, Feng

doi:10.1029/2006gl026867

Cited by 109 publications

(166 citation statements)

References 15 publications

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“…In the transient simulations presented here, the mass upwelling also increases and there is also a simple relationship with the inverse age of air (Austin and Li, 2006). The consequences are that over time chemical constituents had a shorter stratospheric timescale and the large scale tropical ascent rate increased.…”

Section: S To 25mentioning

confidence: 85%

Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model

2007

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Abstract.The results from three 45-year simulations of a coupled chemistry climate model are analysed for solar cycle influences on ozone and temperature. The simulations include UV forcing at the top of the atmosphere, which includes a generic 27-day solar rotation effect as well as the observed monthly values of the solar fluxes. The results are analysed for the 27-day and 11-year cycles in temperature and ozone. In accordance with previous results, the 27-day cycle results are in good qualitative agreement with observations, particularly for ozone. However, the results show significant variations, typically a factor of two or more in sensitivity to solar flux, depending on the solar cycle.In the lower and middle stratosphere we show good agreement also between the modelled and observed 11-year cycle results for the ozone vertical profile averaged over low latitudes. In particular, the minimum in solar response near 20 hPa is well simulated. In comparison, experiments of the model with fixed solar phase (solar maximum/solar mean) and climatological sea surface temperatures lead to a poorer simulation of the solar response in the ozone vertical profile, indicating the need for variable phase simulations in solar sensitivity experiments. The role of sea surface temperatures and tropical upwelling in simulating the ozone minimum response are also discussed.

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Section: S To 25mentioning

confidence: 85%

Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model

2007

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“…The decrease in CO 2 values above the tropopause is mainly caused by the high values of CO 2 in the Northern Hemisphere troposphere during spring, while the air above the tropopause partly entered through the tropical tropopause and partly during late summer of the preceding year when tropospheric CO 2 values were lower due to the seasonal cycle (Bönisch et al, 2009). CH 4 and CO 2 show some fine structures in the stratosphere during both flights.…”

Section: Lindenberg 2016mentioning

confidence: 95%

“…Long-term trends in mean age have been used to investigate long-term changes in the overall overturning circulation of the stratosphere (Brewer-Dobson circulation, BDC). An increase in the strength of the BDC is expected from model calculation with increasing greenhouse gas concentrations (Austin and Li, 2006;Butchart et al, 2006;Butchart, 2014). This is reflected in overall shorter transit times, thus also lower mean age values in the models.…”

Section: Introductionmentioning

confidence: 99%

“…The error in mean age due to this simplification is less than half a month. CO 2 has a seasonal cycle in the troposphere which can propagate into the lower stratosphere (Andrews et al, 2001a, b;Hintsa et al, 1998;Bönisch et al, 2009;Engel et al, 2006a). Rosenlof et al (1997) found that the seasonal cycle in water vapour is observable up to potential temper- atures of about 450 K and termed this region the tropically controlled transition layer.…”

Section: Age Of Air From Aircorementioning

confidence: 99%

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Mean age of stratospheric air derived from AirCore observations

et al. 2017

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Abstract. Mean age of stratospheric air can be derived from observations of sufficiently long-lived trace gases with approximately linear trends in the troposphere. Mean age can serve as a tracer to investigate stratospheric transport and long-term changes in the strength of the overturning BrewerDobson circulation of the stratosphere. For this purpose, a low-cost method is required in order to allow for regular observations up to altitudes of about 30 km. Despite the desired low costs, high precision and accuracy are required in order to determine mean age. We present balloonborne AirCore observations from two midlatitude sites: Timmins in Ontario/Canada and Lindenberg in Germany. During the Timmins campaign, five AirCores sampled air in parallel with a large stratospheric balloon and were analysed for CO 2 , CH 4 and partly CO. We show that there is good agreement between the different AirCores (better than 0.1 %), especially when vertical gradients are small. The measurements from Lindenberg were performed using small low-cost balloons and yielded very comparable results. We have used the observations to extend our long-term data set of mean age observations at Northern Hemisphere midlatitudes. The time series now covers more than 40 years and shows a small, statistically non-significant positive trend of 0.15 ± 0.18 years decade −1 . This trend is slightly smaller than the previous estimate of 0.24 ± 0.22 years decade −1 which was based on observations up to the year 2006. These observations are still in contrast to strong negative trends of mean age as derived from some model calculations.

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“…An acceleration of the Brewer-Dobson circulation (BDC) as a consequence of global warming has been predicted by climate models (Austin et al, 2007;Austin and Li, 2006;Garcia and Randel, 2008;McLandress and Shepherd, 2009;Oman et al, 2009;SPARC CCMVal, 2010). The mean age of stratospheric air (AoA), used as a diagnostic of the strength of the BDC (Waugh and Hall, 2002), is expected to decrease since an air parcel would need less time from the stratospheric entry point at the tropical tropopause to its actual location (Waugh, 2009).…”

Section: Introductionmentioning

confidence: 99%

Shift of subtropical transport barriers explains observed hemispheric asymmetry of decadal trends of age of air

Stiller

Fierli

Ploeger³

et al. 2017

Atmos. Chem. Phys.

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Abstract. In response to global warming, the BrewerDobson circulation in the stratosphere is expected to accelerate and the mean transport time of air along this circulation to decrease. This would imply a negative stratospheric age of air trend, i.e. an air parcel would need less time to travel from the tropopause to any point in the stratosphere. Age of air as inferred from tracer observations, however, shows zero to positive trends in the northern mid-latitude stratosphere and zonally asymmetric patterns. Using satellite observations and model calculations we show that the observed latitudinal and vertical patterns of the decadal changes of age of air in the lower to middle stratosphere during the period 2002-2012 are predominantly caused by a southward shift of the circulation pattern by about 5 • . After correction for this shift, the observations reveal a hemispherically almost symmetric decrease of age of air in the lower to middle stratosphere up to 800 K of up to −0.25 years over the 2002-2012 period with strongest decrease in the northern tropics. This net change is consistent with long-term trends from model predictions.

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On the relationship between the strength of the Brewer‐Dobson circulation and the age of stratospheric air

Cited by 109 publications

References 15 publications

Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model

Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model

Mean age of stratospheric air derived from AirCore observations

Shift of subtropical transport barriers explains observed hemispheric asymmetry of decadal trends of age of air

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