Preprints
https://doi.org/10.5194/amt-2020-461
https://doi.org/10.5194/amt-2020-461

  19 Jan 2021

19 Jan 2021

Review status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

Testing the altitude attribution and vertical resolution of AirCore measurements with a new spiking method

Thomas Wagenhäuser, Andreas Engel, and Robert Sitals Thomas Wagenhäuser et al.
  • Institute for Atmospheric and Environmental Sciences, University of Frankfurt, Frankfurt, 60438, Germany

Abstract. AirCores have been increasingly used to capture vertical profiles of trace gases reaching from the ground up to about 30 km, in order to validate remote sensing instruments and to investigate transport processes in the stratosphere. When deployed to a weather balloon, accurately attributing the trace gas measurements to the sampling altitudes is non-trivial especially in the stratosphere. In this paper we present the CO-spiking experiment, which can be deployed to any AirCore on any platform in order to evaluate different computational altitude attribution processes and to experimentally derive the vertical resolution of the profile by injecting small volumes of signal gas at predefined GPS-altitudes during sampling. We performed two CO-spiking flights with an AirCore from the Goethe-University of Frankfurt (GUF) deployed to a weather balloon in Traînou, France in June 2019. The altitude retrieval based on an instantaneous pressure equilibrium assumption slightly overestimates the sampling altitudes, especially at the top of the profiles. For these two flights our altitude attribution is accurate within 250 m below 20 km. Above 20 km the bias becomes larger and reaches up to 1.2 km at 27 km altitude. Differences in descent velocities are uncovered to have a major impact on the altitude attribution bias. We identified the time lag between the theoretically attributed altitude and the actual CO-spike release altitude to be a possible empirical correction parameter for our AirCore altitude retrieval across different flights. Regarding the corrected profiles, the altitude attribution is accurate within 120 m throughout the profile. Further investigations are needed in order to test for the scope of validity of this correction parameter regarding different ambient conditions and maximum flight altitudes. We derive the vertical resolution from the CO-spikes of both flights and compare it to the modelled vertical resolution. The modelled vertical resolution is better than the experimentally derived resolution throughout the profile, albeit agrees within 220 m. All our findings derived from the two CO-spiking flights are strictly bound to the GUF AirCore dimensions. The newly introduced CO-spiking experiment can be used to test different combinations of AirCore configurations and platforms in future studies.

Thomas Wagenhäuser et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2020-461', P. P. Tans, 05 Feb 2021
    • AC1: 'Reply on RC1', Thomas Wagenhäuser, 26 Mar 2021
  • RC2: 'Comment on amt-2020-461', William Thomas Sturges, 17 Feb 2021
    • AC2: 'Reply on RC2', Thomas Wagenhäuser, 26 Mar 2021
  • RC3: 'Comment on amt-2020-461', Anna Karion, 22 Feb 2021
    • AC3: 'Reply on RC3', Thomas Wagenhäuser, 26 Mar 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2020-461', P. P. Tans, 05 Feb 2021
    • AC1: 'Reply on RC1', Thomas Wagenhäuser, 26 Mar 2021
  • RC2: 'Comment on amt-2020-461', William Thomas Sturges, 17 Feb 2021
    • AC2: 'Reply on RC2', Thomas Wagenhäuser, 26 Mar 2021
  • RC3: 'Comment on amt-2020-461', Anna Karion, 22 Feb 2021
    • AC3: 'Reply on RC3', Thomas Wagenhäuser, 26 Mar 2021

Thomas Wagenhäuser et al.

Thomas Wagenhäuser et al.

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Short summary
AirCores are increasingly deployed to weather balloons to collect continuous atmospheric samples. We introduce a new technique, that can be used in situ to evaluate different data processing methods that are required to derive vertical trace gas profiles from AirCore measurements after sample recovery. The results from two test flights with a specific AirCore configuration provide evidence for systematic deviations in altitude attribution for the upper levels, which can be empirically corrected.