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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 9, issue 8
Atmos. Meas. Tech., 9, 3513–3525, 2016
https://doi.org/10.5194/amt-9-3513-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Meas. Tech., 9, 3513–3525, 2016
https://doi.org/10.5194/amt-9-3513-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 02 Aug 2016

Research article | 02 Aug 2016

GFIT2: an experimental algorithm for vertical profile retrieval from near-IR spectra

Brian J. Connor1, Vanessa Sherlock2, Geoff Toon3, Debra Wunch4, and Paul O. Wennberg4 Brian J. Connor et al.
  • 1BC Consulting Limited, Martinborough, New Zealand
  • 2National Institute for Water and Atmospheric Research, Wellington, New Zealand
  • 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 4California Institute of Technology, Pasadena, CA, USA

Abstract. An algorithm for retrieval of vertical profiles from ground-based spectra in the near IR is described and tested. Known as GFIT2, the algorithm is primarily intended for CO2, and is used exclusively for CO2 in this paper. Retrieval of CO2 vertical profiles from ground-based spectra is theoretically possible, would be very beneficial for carbon cycle studies and the validation of satellite measurements, and has been the focus of much research in recent years. GFIT2 is tested by application both to synthetic spectra and to measurements at two Total Carbon Column Observing Network (TCCON) sites. We demonstrate that there are approximately 3° of freedom for the CO2 profile, and the algorithm performs as expected on synthetic spectra. We show that the accuracy of retrievals of CO2 from measurements in the 1.61μ (6220 cm−1) spectral band is limited by small uncertainties in calculation of the atmospheric spectrum. We investigate several techniques to minimize the effect of these uncertainties in calculation of the spectrum. These techniques are somewhat effective but to date have not been demonstrated to produce CO2 profile retrievals with sufficient precision for applications to carbon dynamics. We finish by discussing ongoing research which may allow CO2 profile retrievals with sufficient accuracy to significantly improve the scientific value of the measurements from that achieved with column retrievals.

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An algorithm for retrieval of vertical profiles of CO2 from ground-based spectra is described. Retrieval of CO2 vertical profiles from would be very beneficial for carbon cycle studies and the validation of satellite measurements. There are approximately 3 degrees of freedom for the CO2 profile. The accuracy of retrievals of CO2 from the spectral band used is limited by small errors in the calculated spectrum. Ongoing research is needed and described.
An algorithm for retrieval of vertical profiles of CO2 from ground-based spectra is described....
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