Stratospheric Mean Ages and Transport Rates from Observations of Carbon Dioxide and Nitrous Oxide

Boering, K. A.; Wofsy, Steven C.; Daube, Bruce C.; Schneider, Hans R.; Loewenstein, M.; Podolske, James R.

doi:10.1126/science.274.5291.1340

Cited by 220 publications

(218 citation statements)

References 25 publications

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“…For completeness, we compare the CLaMS simulated mean age of air with this data set. Figure A1 compares latitudinal profiles of CLaMS simulated mean age of air at 20 km, AoA based on MIPAS observations of SF 6 [Haenel et al, 2014] and on airborne in situ observations of SF 6 and CO 2 (same data as shown in Waugh and Hall [2002], based on various measurements, [Boering et al, 1996;Andrews et al, 2001;Elkins et al, 1996;Ray et al, 1999;Harnisch et al, 1996]). The shadings show the range of monthly mean values for CLaMS and MIPAS, while the error bars show the range between minimum and maximum in situ observations in each latitude bin.…”

Section: Appendix A: Comparison Of Simulated Mean Age To 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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Section: Appendix A: Comparison Of Simulated Mean Age To 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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“…Although this comparison cannot diagnose the adequacy of the components of transport, such as vertical advection, vertical mixing, and inward mixing, the agreement between the model and observations suggests that the balance of these processes may be good in the model. Unfortunately, the wide range of theta values covered by these N20 bins smears out the high spatial resolution seen in CO2/theta profiles [see Boering et al, 1996]. Meaningful information can be obtained with 5-K-wide theta bins, whereas it is not possible to use an N20 bin narrow enough (i.e., <1 ppb) to give the equivalent spatial resolution, in part due to measurement precision.…”

Section: Diagnosis Of Model Transport and Comparison With Observationmentioning

confidence: 99%

“…Observations show that this large-amplitude seasonal cycle can be transported away from its source in the northern hemisphere (NH), for example, to the southern hemisphere (SH) upper troposphere or upward through the tropical tropopause. The time to transport this signal and the amount of attenuation it undergoes due to mixing are useful for diagnosing transport in the upper troposphere and lower stratosphere (UT/LS) [Nakazawa et al, 1991; Boering et al, 1996]. Nakazawa et al [1991] studied CO2 seasonal cycles in the UT/LS.…”

Section: Introductionmentioning

confidence: 99%

The CO₂ seasonal cycle as a tracer of transport

Strahan¹,

Douglass²,

Nielsen³

et al. 1998

J. Geophys. Res.

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Abstract. CO2 time series in the lower stratosphere have been constructed as a function of latitude and altitude using ER-2 aircraft observations. A seasonally varying signal derived from tropical surface CO 2 data was fit to these data in a manner similar to that of Boering et al. [1996]. This analysis shows how the tropospheric CO2 seasonal cycle in air entering the tropical lower stratosphere ascends and gradually loses amplitude. The midlatitude results show that in the 370-to 400-K range the tropical signal is transported poleward rapidly with only a small loss in amplitude. The signal also reaches the midlatitudes rapidly at higher altitudes but with markedly less amplitude. Above --•440 K the midlatitude CO 2 data best fit a line whose slope is the secular increase in CO2. This observational analysis is used as a basis for diagnosing transport in a CO2 simulation produced using GEOS-1 Data Assimilation System (DAS) winds in an off-line chemistry and transport model. The model is forced at the lowest levels by a 5-year zonal mean CO2 data set derived from surface observations. The analysis of model results as a function of height and latitude determines whether (1) the seasonally varying CO2 cycle forced in the troposphere survives in the tropical lower stratosphere and whether (2) the CO2 cycle in the tropical lower stratosphere propagates realistically to the midlatitudes. We find that the model transports a CO2 seasonal cycle from the surface to the tropical upper troposphere that agrees with the phase and amplitude of tropospheric aircraft measurements. The cycle input into the model tropical lower stratosphere attenuates with height in a reasonable way compared with observations. The phase and amplitude of the cycle transported from the tropics to the midlatitudes agree well with the data up to about 440 K, but above that the model transports more of the tropical signal to the midlatitudes than is suggested by the ER-2 data. Overall, there is remarkable consistency between the model and observations in the upper troposphere/lower stratosphere, which supports the use of assimilated winds in assessments of the effects of aircraft exhaust.

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“…Even the averaged amplitude of about ±3 ppmv in the tropical lower troposphere is twice as large as the yearly growth rate. Thus, the tropospheric seasonal cycle is a dominant appearance which propagates upwards through the tropopause into the LS and spreads out merdionally, as shown by, e.g., Boering et al [1994Boering et al [ , 1996; ST98 and Andrews et al [1999Andrews et al [ , 2001a.…”

Section: Characterization Of Co 2 and Sfmentioning

confidence: 99%

“…Their study is further referred to as ST98. ST98 applied the conceptual framework of Boering et al [1994Boering et al [ , 1996 with the benefit that CO 2 is chemically inert in the troposphere and stratosphere and thus relatively simple to implement in models. Passive tracers offer the great advantage that their distributions are only controlled by transport processes and that no chemistry is involved.…”

Section: Introductionmentioning

confidence: 99%

Model evaluation of CO₂ and SF₆ in the extratropical UT/LS region

et al. 2008

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[1] We evaluate the transport of three-dimensional chemical transport models in the upper troposphere and lower stratosphere applying observed distributions of CO 2 and SF 6 . The data consist of high-resolution in situ observations, obtained during all seasons at subtropical, middle and high latitudes over Western Europe within the SPURT (Spurenstofftransport in der Tropopausenregion) project (2001)(2002)(2003). We show that the combination of the two passive tracers SF 6 and CO 2 with their different tropospheric characteristics and the propagation of the temporal trends of these two gases into the lower stratosphere is a powerful diagnostic for evaluation of model transport. The model evaluation shows that all models are able to capture the general features in the tracer distributions including the vertical and horizontal propagation of the CO 2 seasonal cycle. However, the modeled CO 2 cycles are a few months out of phase in the lowermost stratosphere due to tropospheric mixing. Two models show a too strong Brewer-Dobson circulation causing an overestimation of the tracers in the lowermost stratosphere during winter and spring. One model displays a too strong tropical isolation leading to an underestimation of the tracers in the lowermost stratosphere during winter. All models suffer to some extend from diffusion and/or too strong mixing across the tropopause. In addition, the models show too weak vertical upward transport into the upper troposphere during the boreal summer. Sensitivity studies show that our initial conditions and boundary constraints are realistic and that a horizontal resolution higher than 2 degrees and an increase of the meteorology update frequency (from 6 to 3-hourly) have negligible impact on the modeled CO 2 and SF 6 distributions.

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Stratospheric Mean Ages and Transport Rates from Observations of Carbon Dioxide and Nitrous Oxide

Cited by 220 publications

References 25 publications

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

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

The CO₂ seasonal cycle as a tracer of transport

Model evaluation of CO₂ and SF₆ in the extratropical UT/LS region

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Stratospheric Mean Ages and Transport Rates from Observations of Carbon Dioxide and Nitrous Oxide

Cited by 220 publications

References 25 publications

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

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

The CO2 seasonal cycle as a tracer of transport

Model evaluation of CO2 and SF6 in the extratropical UT/LS region

Contact Info

Product

Resources

About

The CO₂ seasonal cycle as a tracer of transport

Model evaluation of CO₂ and SF₆ in the extratropical UT/LS region