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Published November 18, 2015 | Published
Journal Article Open

Simulated retrievals for the remote sensing of CO_2, CH_4, CO, and H_2O from geostationary orbit

Abstract

The Geostationary Fourier Transform Spectrometer (GeoFTS) is designed to measure high-resolution spectra of reflected sunlight in three near-infrared bands centered around 0.76, 1.6, and 2.3 μm and to deliver simultaneous retrievals of column-averaged dry air mole fractions of CO_2, CH_4, CO, and H_2O (denoted XCO_2, XCH_4, XCO, and XH_2O, respectively) at different times of day over North America. In this study, we perform radiative transfer simulations over both clear-sky and all-sky scenes expected to be observed by GeoFTS and estimate the prospective performance of retrievals based on results from Bayesian error analysis and characterization. We find that, for simulated clear-sky retrievals, the average retrieval biases and single-measurement precisions are < 0.2 % for XCO_2, XCH_4, and XH_2O, and < 2 % for XCO, when the a priori values have a bias of 3 % and an uncertainty of 3 %. In addition, an increase in the amount of aerosols and ice clouds leads to a notable increase in the retrieval biases and slight worsening of the retrieval precisions. Furthermore, retrieval precision is a strong function of signal-to-noise ratio and spectral resolution. This simulation study can help guide decisions on the design of the GeoFTS observing system, which can result in cost-effective measurement strategies while achieving satisfactory levels of retrieval precisions and biases. The simultaneous retrievals at different times of day will be important for more accurate estimation of carbon sources and sinks on fine spatiotemporal scales and for studies related to the atmospheric component of the water cycle.

Additional Information

© 2015 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 21 April 2015 – Published in Atmos. Meas. Tech. Discuss.: 12 June 2015; Revised: 3 September 2015 – Accepted: 5 October 2015 – Published: 18 November 2015. The authors would like to thank Renyu Hu, Pushkar Kopparla, Michael Wong, Le Kuai, Clare (Kam Weng) Wong, and Dejian Fu for helpful discussions. The authors also appreciate technical support from Michael Black and administrative support from Margaret Carlos and Irma Black. Valuable comments and suggestions from two reviewers are greatly appreciated. This research was supported in part by NASA grant NNX13AK34G to the California Institute of Technology, grant P1367828 from the Jet Propulsion Laboratory, and the KISS program at California Institute of Technology.

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August 20, 2023
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