Articles | Volume 10, issue 7
Atmos. Meas. Tech., 10, 2727–2743, 2017
Atmos. Meas. Tech., 10, 2727–2743, 2017

Research article 28 Jul 2017

Research article | 28 Jul 2017

MIPAS IMK/IAA carbon tetrachloride (CCl4) retrieval and first comparison with other instruments

Ellen Eckert1, Thomas von Clarmann1, Alexandra Laeng1, Gabriele P. Stiller1, Bernd Funke1, Norbert Glatthor1, Udo Grabowski1, Sylvia Kellmann1, Michael Kiefer1, Andrea Linden1, Arne Babenhauserheide1, Gerald Wetzel1, Christopher Boone2, Andreas Engel3, Jeremy J. Harrison4,5,6, Patrick E. Sheese7, Kaley A. Walker2,7, and Peter F. Bernath2,8 Ellen Eckert et al.
  • 1Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
  • 2Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada
  • 3Institut für Atmosphäre und Umwelt, J. W. Goethe Universität, Frankfurt, Germany
  • 4Department of Physics, University of Leicester, University Road, Leicester LE1 7RH, UK
  • 5National Centre for Earth Observation, University of Leicester, University Road, Leicester LE1 7RH, UK
  • 6Leicester Institute for Space and Earth Observation, University of Leicester, University Road, Leicester LE1 7RH, UK
  • 7Department of Physics, University of Toronto, Toronto, Ontario, Canada
  • 8Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, VA 23529-0126, USA

Abstract. MIPAS thermal limb emission measurements were used to derive vertically resolved profiles of carbon tetrachloride (CCl4). Level-1b data versions MIPAS/5.02 to MIPAS/5.06 were converted into volume mixing ratio profiles using the level-2 processor developed at Karlsruhe Institute of Technology (KIT) Institute of Meteorology and Climate Research (IMK) and Consejo Superior de Investigaciones Científicas (CSIC), Instituto de Astrofísica de Andalucía (IAA). Consideration of peroxyacetyl nitrate (PAN) as an interfering species, which is jointly retrieved, and CO2 line mixing is crucial for reliable retrievals. Parts of the CO2 Q-branch region that overlap with the CCl4 signature were omitted, since large residuals were still found even though line mixing was considered in the forward model. However, the omitted spectral region could be narrowed noticeably when line mixing was accounted for. A new CCl4 spectroscopic data set leads to slightly smaller CCl4 volume mixing ratios. In general, latitude–altitude cross sections show the expected CCl4 features with highest values of around 90 pptv at altitudes at and below the tropical tropopause and values decreasing with altitude and latitude due to stratospheric decomposition. Other patterns, such as subsidence in the polar vortex during winter and early spring, are also visible in the distributions. The decline in CCl4 abundance during the MIPAS Envisat measurement period (July 2002 to April 2012) is clearly reflected in the altitude–latitude cross section of trends estimated from the entire retrieved data set.

Short summary
We retrieved vertical profiles of CCl4 from MIPAS Envisat IMK/IAA data. A detailed description of all characteristics is included in the paper as well as comparisons with historical measurements and comparisons with collocated measurements of instruments covering the same time span as MIPAS Envisat. A particular focus also lies on the usage of a new CCl4 spectroscopic dataset introduced recently, which leads to more realistic CCl4 volume mixing ratios.