Retrieval of xCO2 from ground-based mid-infrared (NDACC) solar absorption spectra and comparison to TCCON

• Published in: Atmospheric Measurement Techniques
• Main Authors: Buschmann, Matthias, Deutscher, Nicholas M., Sherlock, Vanessa, Palm, Mathias, Warneke, Thorsten, Notholt, Justus
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2016
• Subjects: article; Verlagsveröffentlichung; Ny-Ålesund; Ny Ålesund; Spitsbergen
• Online Access: https://doi.org/10.5194/amt-9-577-2016; https://noa.gwlb.de/receive/cop_mods_00014004; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00013960/amt-9-577-2016.pdf; https://amt.copernicus.org/articles/9/577/2016/amt-9-577-2016.pdf

High-resolution solar absorption spectra, taken within the Network for the Detection of Atmospheric Composition Change Infrared Working Group (NDACC-IRWG) in the mid-infrared spectral region, are used to infer partial or total column abundances of many gases. In this paper we present the retrieval of a column-averaged mole fraction of carbon dioxide from NDACC-IRWG spectra taken with a Fourier transform infrared (FTIR) spectrometer at the site in Ny-Ålesund, Spitsbergen. The retrieved time series is compared to colocated standard TCCON (Total Carbon Column Observing Network) measurements of column-averaged dry-air mole fractions of CO2 (denoted by xCO2). Comparing the NDACC and TCCON retrievals, we find that the sensitivity of the NDACC retrieval is lower in the troposphere (by a factor of 2) and higher in the stratosphere, compared to TCCON. Thus, the NDACC retrieval is less sensitive to tropospheric changes (e.g., the seasonal cycle) in the column average.