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Volume 9, issue 4 | Copyright

Special issue: Limb observations of the middle atmosphere by space- and airborne...

Atmos. Meas. Tech., 9, 1485-1503, 2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 06 Apr 2016

Research article | 06 Apr 2016

Stratospheric CH4 and CO2 profiles derived from SCIAMACHY solar occultation measurements

Stefan Noël1, Klaus Bramstedt1, Michael Hilker1, Patricia Liebing1, Johannes Plieninger2, Max Reuter1, Alexei Rozanov1, Christopher E. Sioris3, Heinrich Bovensmann1, and John P. Burrows1 Stefan Noël et al.
  • 1Institute of Environmental Physics, University of Bremen, FB 1, P.O. Box 330440, 28334 Bremen, Germany
  • 2KIT, IMK-ASF, P.O. Box 3640, 76021 Karlsruhe, Germany
  • 3Centre for Research in Earth and Space Science, York University, 4700 Keele Street, Toronto, ON, M3J 1P3 Canada

Abstract. Stratospheric profiles of methane (CH4) and carbon dioxide (CO2) have been derived from solar occultation measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). The retrieval is performed using a method called onion peeling DOAS (ONPD), which combines an onion peeling approach with a weighting function DOAS (differential optical absorption spectroscopy) fit in the spectral region between 1559 and 1671nm. By use of updated pointing information and optimisation of the data selection as well as of the retrieval approach, the altitude range for reasonable CH4 could be broadened from 20 to 40km to about 17 to 45km. Furthermore, the quality of the derived CO2 has been assessed such that now the first stratospheric profiles (17–45km) of CO2 from SCIAMACHY are available. Comparisons with independent data sets yield an estimated accuracy of the new SCIAMACHY stratospheric profiles of about 5–10% for CH4 and 2–3% for CO2. The accuracy of the products is currently mainly restricted by the appearance of unexpected vertical oscillations in the derived profiles which need further investigation. Using the improved ONPD retrieval, CH4 and CO2 stratospheric data sets covering the whole SCIAMACHY time series (August 2002–April 2012) and the latitudinal range between about 50 and 70°N have been derived. Based on these time series, CH4 and CO2 trends have been estimated. CH4 trends above about 20km are not significantly different from zero and the trend at 17km is about 3ppbvyear−1. The derived CO2 trends show a general decrease with altitude with values of about 1.9ppmvyear−1 at 21km and about 1.3ppmvyear−1 at 39km. These results are in reasonable agreement with total column trends for these gases. This shows that the new SCIAMACHY data sets can provide valuable information about the stratosphere.

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Short summary
Stratospheric methane (CH4) and carbon dioxide (CO2) profiles have been derived from solar occultation measurements of the SCIAMACHY satellite instrument. The accuracy of these profiles is estimated to be about 5–10 % for CH4 and 2–3 % for CO2, mainly limited by unexpected vertical oscillations. Results are available for August 2002 to April 2012 and latitudes between about 50 and 70° N. From these, time series trends have been estimated, which are in reasonable agreement with total column trends.
Stratospheric methane (CH4) and carbon dioxide (CO2) profiles have been derived from solar...