Articles | Volume 6, issue 12
Atmos. Meas. Tech., 6, 3527–3537, 2013
Atmos. Meas. Tech., 6, 3527–3537, 2013

Research article 16 Dec 2013

Research article | 16 Dec 2013

Calibration of sealed HCl cells used for TCCON instrumental line shape monitoring

F. Hase1, B. J. Drouin2, C. M. Roehl3, G. C. Toon2, P. O. Wennberg3, D. Wunch3, T. Blumenstock1, F. Desmet4, D. G. Feist5, P. Heikkinen6, M. De Mazière4, M. Rettinger8, J. Robinson9, M. Schneider1, V. Sherlock9, R. Sussmann8, Y. Té10, T. Warneke7, and C. Weinzierl7 F. Hase et al.
  • 1Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research (IMK-ASF), Karlsruhe, Germany
  • 2Jet Propulsion Laboratory, Pasadena, CA 91109, USA
  • 3California Institute of Technology, Pasadena, CA 91125, USA
  • 4Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
  • 5Max Planck Institute for Biogeochemistry, Jena, Germany
  • 6Finnish Meteorological Institute, Sodankylä, Finland
  • 7Institute of Environmental Physics, University of Bremen, Germany
  • 8Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research (IMK-IFU), Garmisch-Partenkirchen, Germany
  • 9NIWA, Lauder, New Zealand
  • 10UPMC Univ. Paris06, Laboratoire de Physique Moléculaire pour l'Atmosphère et l'Astrophysique (LPMAA), UMR7092, CNRS, Paris, France

Abstract. The TCCON (Total Carbon Column Observing Network) FTIR (Fourier transform infrared) network provides highly accurate observations of greenhouse gas column-averaged dry-air mole fractions. As an important component of TCCON quality assurance, sealed cells filled with approximately 5 mbar of HCl are used for instrumental line shape (ILS) monitoring at all TCCON sites. Here, we introduce a calibration procedure for the HCl cells which employs a refillable, pressure-monitored reference cell filled with C2H2. Using this method, we identify variations of HCl purity between the TCCON cells as a non-negligible disturbance. The new calibration procedure introduced here assigns effective pressure values to each individual cell to account for additional broadening of the HCl lines. This approach will improve the consistency of the network by significantly reducing possible station-to-station biases due to inconsistent ILS results from different HCl cells. We demonstrate that the proposed method is accurate enough to turn the ILS uncertainty into an error source of secondary importance from the viewpoint of network consistency.