Articles | Volume 8, issue 8
Atmos. Meas. Tech., 8, 3315–3336, 2015

Special issue: Observing Atmosphere and Climate with Occultation Techniques...

Atmos. Meas. Tech., 8, 3315–3336, 2015

Research article 14 Aug 2015

Research article | 14 Aug 2015

Retrieval and validation of carbon dioxide, methane and water vapor for the Canary Islands IR-laser occultation experiment

V. Proschek1, G. Kirchengast1, S. Schweitzer2,1, J. S. A. Brooke3, P. F. Bernath3,4, C. B. Thomas3, J.-G. Wang3, K. A. Tereszchuk3,5, G. González Abad3,6, R. J. Hargreaves3,4, C. A. Beale3,4, J. J. Harrison3, P. A. Martin7, V. L. Kasyutich7,8, C. Gerbig9, O. Kolle9, and A. Loescher10 V. Proschek et al.
  • 1Wegener Center for Climate and Global Change (WEGC) and Institute for Geophysics, Astrophysics and Meteorology/Institute of Physics, University of Graz, Graz, Austria
  • 2Institute for Surface Technologies and Photonics, Joanneum Research Forschungsgesellschaft mbH, Weiz, Austria
  • 3Department of Chemistry, University of York, York, UK
  • 4Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, USA
  • 5Environment Canada, Toronto, Ontario, Canada
  • 6Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA
  • 7School of Chemical Engineering and Analytical Science, University of Manchester, Manchester, UK
  • 8Servomex, Jarvis Brook, Crowborough, UK
  • 9Biogeochemical Systems Department, Max Planck Institute for Biogeochemistry, Jena, Germany
  • 10Earth Observation Future Missions Division, ESA/ESTEC, Noordwijk, the Netherlands

Abstract. The first ground-based experiment to prove the concept of a novel space-based observation technique for microwave and infrared-laser occultation between low-Earth-orbit satellites was performed in the Canary Islands between La Palma and Tenerife. For two nights from 21 to 22 July 2011 the experiment delivered the infrared-laser differential transmission principle for the measurement of greenhouse gases (GHGs) in the free atmosphere. Such global and long-term stable measurements of GHGs, accompanied also by measurements of thermodynamic parameters and line-of-sight wind in a self-calibrating way, have become very important for climate change monitoring. The experiment delivered promising initial data for demonstrating the new observation concept by retrieving volume mixing ratios of GHGs along a ~144 km signal path at altitudes of ~2.4 km. Here, we present a detailed analysis of the measurements, following a recent publication that introduced the experiment's technical setup and first results for an example retrieval of CO2. We present the observational and validation data sets, the latter simultaneously measured at the transmitter and receiver sites; the measurement data handling; and the differential transmission retrieval procedure. We also determine the individual and combined uncertainties influencing the results and present the retrieval results for 12CO2, 13CO2, C18OO, H2O and CH4. The new method is found to have a reliable basis for monitoring of greenhouse gases such as CO2, CH4, and H2O in the free atmosphere.