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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2016-1163
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
02 Mar 2017
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.
CCl4 distribution derived from MIPAS ESA V7 data: validation, trend and lifetime estimation
Massimo Valeri1,2, Flavio Barbara3, Chris Boone4, Simone Ceccherini3, Marco Gai3, Guido Maucher6, Piera Raspollini3, Marco Ridolfi1,3, Luca Sgheri5, Gerald Wetzel6, and Nicola Zoppetti3 1Dipartimento di Fisica e Astronomia, Università di Bologna, Italy
2Istituto di Scienze dell’Atmosfera e del Clima, Consiglio Nazionale delle Ricerche, Bologna, Italy
3Istituto di Fisica Applicata “Carrara”, Consiglio Nazionale delle Ricerche, Firenze, Italy
4Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada
5Istituto per le Applicazioni del Calcolo, Consiglio Nazionale delle Ricerche, Firenze, Italy
6Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
Abstract. Atmospheric emissions of Carbon tetrachloride CCl4 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 CCl4,'' the discrepancy between atmospheric observations and reported production and consumption. Surface measurements of CCl4 atmospheric concentrations have declined at a rate almost three times smaller than its lifetime-limited rate, suggesting persistent atmospheric emissions despite the ban. In this paper, we study CCl4 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 CCl4 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. In the troposphere, the largest concentrations are observed at the latitudes of major industrial countries (20/50°N). The good agreement we find between MIPAS CCl4 and independent measurements from other satellite and balloon-borne remote sounders proves the reliability of the MIPAS dataset.

CCl4 trends are calculated as a function of both latitude and altitude. Negative trends are found at all latitudes in the upper-troposphere / lower-stratosphere region, apart from a region in the Southern mid-latitudes between 50 and 10 hPa where the trend is positive. At the lowest altitudes sounded by MIPAS, we find trends consistent with those determined on the basis of long-term ground-based measurements. For higher altitudes, the trend shows a pronounced asymmetry between Northern and Southern Hemispheres, and the magnitude of the decline rate increases with altitude. At 50 hPa the decline is about 30–35 %/decade, close to the lifetime-limited trend.

We use a simplified model assuming tracer-tracer linear correlations to determine CCl4 lifetime in the lower stratosphere. The calculation provides a global average lifetime of 46(38–60) years considering CFC-11 as the reference tracer. This value is consistent with the most recent literature result of 44(36–58) years.


Citation: Valeri, M., Barbara, F., Boone, C., Ceccherini, S., Gai, M., Maucher, G., Raspollini, P., Ridolfi, M., Sgheri, L., Wetzel, G., and Zoppetti, N.: CCl4 distribution derived from MIPAS ESA V7 data: validation, trend and lifetime estimation, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2016-1163, in review, 2017.
Massimo Valeri et al.
Massimo Valeri et al.

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Short summary
Atmospheric emissions of CCl4 are regulated by the Montreal Protocol due to its role as a strong ozone-depleting substance. The molecule is subject of recent increased interest as a consequence of the discrepancy between atmospheric observations and reported production and consumption. We use MIPAS/ENVISAT data (2002–2012) to estimate CCl4 trends and lifetime. At 50 hPa we find a decline of about 30–35 % / decade. In the lower stratosphere our lifetime estimate is 46(38–60) years.
Atmospheric emissions of CCl4 are regulated by the Montreal Protocol due to its role as a strong...
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