Decrease of the carbon tetrachloride (CCl4) loading above Jungfraujoch, based on high resolution infrared solar spectra recorded between 1999 and 2011

Rinsland, C. P.; Mahieu, Emmanuel; Demoulin, Philippe; Zander, Rodolphe; Servais, Christian; Hartmann, Jean‐Michel

doi:10.1016/j.jqsrt.2012.02.016

Cited by 12 publications

(10 citation statements)

References 39 publications

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“…AGAGE and the University of California, Irvine (UCI) networks report rates of decline of 1.2-1.3 % yr −1 from 2011 to 2012, whereas the rate of decline reported by the NOAA/HATS network was 1.6 % yr −1 . These relative declines in mole fractions at the Earth's surface are comparable to declines in column abundances of 1.1-1.2 % yr −1 (Brown et al, 2011;Rinsland et al, 2012).…”

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confidence: 69%

CCl<sub>4</sub> distribution derived from MIPAS ESA v7 data: intercomparisons, trend, and lifetime estimation

et al. 2017

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Abstract. Atmospheric emissions of carbon tetrachloride (CCl 4 ) are regulated by the Montreal Protocol due to its role as a strong ozone-depleting substance. The molecule has been the subject of recent increased interest as a consequence of the so-called "mystery of CCl 4 ", the discrepancy between atmospheric observations and reported production and consumption. Surface measurements of CCl 4 atmospheric concentrations have declined at a rate almost 3 times lower than its lifetime-limited rate, suggesting persistent atmospheric emissions despite the ban. In this paper, we study CCl 4 vertical and zonal distributions in the upper troposphere and lower stratosphere (including the photolytic loss region, 70-20 hPa), its trend, and its stratospheric lifetime using measurements from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), which operated onboard the ENVISAT satellite from 2002 to 2012. Specifically, we use the MIPAS data product generated with Version 7 of the Level 2 algorithm operated by the European Space Agency.The CCl 4 zonal means show features typical of long-lived species of anthropogenic origin that are destroyed primarily in the stratosphere, with larger quantities in the troposphere and a monotonic decrease with increasing altitude in the stratosphere. MIPAS CCl 4 measurements have been compared with independent measurements from other satellite and balloon-borne remote sounders, showing a good agreement between the different datasets.CCl 4 trends are calculated as a function of both latitude and altitude. Negative trends of about −10 to −15 pptv decade −1 (−10 to −30 % decade −1 ) are found at all latitudes in the upper troposphere-lower stratosphere region, apart from a region in the southern midlatitudes between 50 and 10 hPa where the trend is positive with values around 5-10 pptv decade −1 (15-20 % decade −1 ). At the lowest altitudes sounded by MIPAS, we find trends consistent with those determined on the basis of long-term ground-based measurements (−10 to −13 pptv decade −1 ). For higher altitudes, the trend shows a pronounced asymmetry between the Northern and Southern hemispheres, and the magnitude of the decline rate increases with altitude. We use a simplified model assuming tracer-tracer linear correlations to determine CCl 4 lifetime in the lower stratosphere. The calculation provides a global average lifetime of 47 (39-61) years, considering CFC-11 as the reference tracer. This value is consistent with the most recent literature result of 44 (36-58) years.

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confidence: 69%

CCl<sub>4</sub> distribution derived from MIPAS ESA v7 data: intercomparisons, trend, and lifetime estimation

et al. 2017

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“…A total column time series spanning the 1999-2015 period, updated to be consistent with Rinsland et al (2012), is available from the Jungfraujoch station (Swiss Alps, 46.5 • N, 8 • E, 3580 m a.s.l.) and will be used here, but an effort is ongoing to retrieve CCl 4 from other NDACC sites (Network for the Detection of Atmospheric Composition Change; see http://www.ndacc.org).…”

Section: Ndacc Column CCL 4 Observationsmentioning

confidence: 99%

“…and will be used here, but an effort is ongoing to retrieve CCl 4 from other NDACC sites (Network for the Detection of Atmospheric Composition Change; see http://www.ndacc.org). Rinsland et al (2012) provide a thorough description of the approach which allows the retrieval of CCl 4 total columns from ground-based FTIR (Fourier transform infrared) solar absorption spectra. Briefly, the strong CCl 4 ν 3 band at 794 cm −1 is used, and a broad window spanning the 785-807 cm −1 spectral range is fitted, accounting for main interferences by H 2 O, CO 2 and O 3 , as well as by a dozen second-and third-order absorbers.…”

Section: Ndacc Column CCL 4 Observationsmentioning

confidence: 99%

“…An initial comparison between the observed and modelled columns indicated a bias of about 15 %, with TOMCAT lying below the FTIR data. Since the latter could be affected by a systematic uncertainty of up to 10-11 % (see Table 1 in Rinsland et al, 2012), we allowed for a × 0.9 scaling of the column amounts. Figure 3 shows the model still tends to underestimate the scaled FTIR column by about 0.05 × 10 15 molecules cm −2 (about 5 %).…”

Section: Comparison With Observationsmentioning

confidence: 99%

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Model sensitivity studies of the decrease in atmospheric carbon tetrachloride

et al. 2016

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Abstract. Carbon tetrachloride (CCl 4 ) is an ozone-depleting substance, which is controlled by the Montreal Protocol and for which the atmospheric abundance is decreasing. However, the current observed rate of this decrease is known to be slower than expected based on reported CCl 4 emissions and its estimated overall atmospheric lifetime. Here we use a three-dimensional (3-D) chemical transport model to investigate the impact on its predicted decay of uncertainties in the rates at which CCl 4 is removed from the atmosphere by photolysis, by ocean uptake and by degradation in soils. The largest sink is atmospheric photolysis (74 % of total), but a reported 10 % uncertainty in its combined photolysis cross section and quantum yield has only a modest impact on the modelled rate of CCl 4 decay. This is partly due to the limiting effect of the rate of transport of CCl 4 from the main tropospheric reservoir to the stratosphere, where photolytic loss occurs. The model suggests large interannual variability in the magnitude of this stratospheric photolysis sink caused by variations in transport. The impact of uncertainty in the minor soil sink (9 % of total) is also relatively small. In contrast,Published by Copernicus Publications on behalf of the European Geosciences Union. 15742 M. P. Chipperfield et al.: Model sensitivity studies of the decrease in atmospheric carbon tetrachloride the model shows that uncertainty in ocean loss (17 % of total) has the largest impact on modelled CCl 4 decay due to its sizeable contribution to CCl 4 loss and large lifetime uncertainty range (147 to 241 years). With an assumed CCl 4 emission rate of 39 Gg year −1 , the reference simulation with the best estimate of loss processes still underestimates the observed CCl 4 (overestimates the decay) over the past 2 decades but to a smaller extent than previous studies. Changes to the rate of CCl 4 loss processes, in line with known uncertainties, could bring the model into agreement with in situ surface and remote-sensing measurements, as could an increase in emissions to around 47 Gg year −1 . Further progress in constraining the CCl 4 budget is partly limited by systematic biases between observational datasets. For example, surface observations from the National Oceanic and Atmospheric Administration (NOAA) network are larger than from the Advanced Global Atmospheric Gases Experiment (AGAGE) network but have shown a steeper decreasing trend over the past 2 decades. These differences imply a difference in emissions which is significant relative to uncertainties in the magnitudes of the CCl 4 sinks.

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“…For the photolysis sink, monthly-mean photolysis rates were calculated using a stand-alone version of the TOM-CAT/SLIMCAT stratospheric chemistry scheme and kinetic data from Sander et al (2011). Hourly model output was averaged to produce monthly-mean photolysis rates as a function of latitude and altitude.…”

Section: Tomcat 3-d Chemical Transport Modelmentioning

confidence: 99%

Response to Reviewer 2

Chipperfield¹

2016

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Carbon tetrachloride (CCl 4 ) is an ozone-depleting substance, which is controlled by the Montreal Protocol and for which the atmospheric abundance is decreasing. However, the current observed rate of this decrease is known to be slower than expected based on reported CCl 4 emissions and its estimated overall atmospheric lifetime. Here we use a three-dimensional (3-D) chemical transport model to investigate the impact on its predicted decay of uncertainties in the rates at which CCl 4 is removed from the atmosphere by photolysis, by ocean uptake and by degradation in soils. The largest sink is atmospheric photolysis (74 % of total), but a reported 10 % uncertainty in its combined photolysis cross section and quantum yield has only a modest impact on the modelled rate of CCl 4 decay. This is partly due to the limiting effect of the rate of transport of CCl 4 from the main tropospheric reservoir to the stratosphere, where photolytic loss occurs. The model suggests large interannual variability in the magnitude of this stratospheric photolysis sink caused by variations in transport. The impact of uncertainty in the minor soil sink (9 % of total) is also relatively small. In contrast,Published by Copernicus Publications on behalf of the European Geosciences Union.

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Decrease of the carbon tetrachloride (CCl4) loading above Jungfraujoch, based on high resolution infrared solar spectra recorded between 1999 and 2011

Cited by 12 publications

References 39 publications

CCl<sub>4</sub> distribution derived from MIPAS ESA v7 data: intercomparisons, trend, and lifetime estimation

CCl<sub>4</sub> distribution derived from MIPAS ESA v7 data: intercomparisons, trend, and lifetime estimation

Model sensitivity studies of the decrease in atmospheric carbon tetrachloride

Response to Reviewer 2

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Decrease of the carbon tetrachloride (CCl4) loading above Jungfraujoch, based on high resolution infrared solar spectra recorded between 1999 and 2011

Cited by 12 publications

References 39 publications

CCl&lt;sub&gt;4&lt;/sub&gt; distribution derived from MIPAS ESA v7 data: intercomparisons, trend, and lifetime estimation

CCl&lt;sub&gt;4&lt;/sub&gt; distribution derived from MIPAS ESA v7 data: intercomparisons, trend, and lifetime estimation

Model sensitivity studies of the decrease in atmospheric carbon tetrachloride

Response to Reviewer 2

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CCl<sub>4</sub> distribution derived from MIPAS ESA v7 data: intercomparisons, trend, and lifetime estimation

CCl<sub>4</sub> distribution derived from MIPAS ESA v7 data: intercomparisons, trend, and lifetime estimation