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

Connor, Brian J. and Sherlock, Vanessa and Toon, Geoff and Wunch, Debra and Wennberg, Paul O. (2016) GFIT2: an experimental algorithm for vertical profile retrieval from near-IR spectra. Atmospheric Measurement Techniques, 9 (8). pp. 3513-3525. ISSN 1867-8548. doi:10.5194/amt-9-3513-2016.

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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.

Item Type:Article
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URLURL TypeDescription
Toon, Geoff0000-0003-4174-7541
Wunch, Debra0000-0002-4924-0377
Wennberg, Paul O.0000-0002-6126-3854
Additional Information:© Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 27 August 2015 – Published in Atmos. Meas. Tech. Discuss.: 23 November 2015; Revised: 29 June 2016 – Accepted: 4 July 2016 – Published: 2 August 2016. Part of this research was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. We thank NASA’s Carbon Cycle Science Investigation Program for supporting the development of GFIT2 (NNX14AI60G). Operations of TCCON at Lamont, Oklahoma, are made possible by NASA’s OCO-2 project in collaboration with the DOE ARM program. Cessna data from the SGP are available through the ARM archive ( We thank Sebastien Biraud for his assistance in interpreting the aircraft data. Edited by: F. Hase. Reviewed by: two anonymous referees.
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Issue or Number:8
Record Number:CaltechAUTHORS:20200528-084127637
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Official Citation:Connor, B. J., Sherlock, V., Toon, G., Wunch, D., and Wennberg, P. O.: GFIT2: an experimental algorithm for vertical profile retrieval from near-IR spectra, Atmos. Meas. Tech., 9, 3513–3525,, 2016
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103514
Deposited By: Tony Diaz
Deposited On:28 May 2020 16:37
Last Modified:16 Nov 2021 18:22

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