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The impact of spectral resolution on satellite retrieval accuracy of CO_2 and CH_4

Galli, A. and Guerlet, S. and Butz, A. and Aben, I. and Suto, H. and Kuze, A. and Deutscher, N. M. and Notholt, J. and Wunch, D. and Wennberg, P. O. and Griffith, D. W. T. and Hasekamp, O. and Landgraf, J. (2014) The impact of spectral resolution on satellite retrieval accuracy of CO_2 and CH_4. Atmospheric Measurement Techniques, 7 (4). pp. 1105-1119. ISSN 1867-8548. https://resolver.caltech.edu/CaltechAUTHORS:20140530-105533786

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Abstract

The Fourier-transform spectrometer on board the Japanese GOSAT (Greenhouse gases Observing SATellite) satellite offers an excellent opportunity to study the impact of instrument resolution on retrieval accuracy of CO_2 and CH_4. This is relevant to further improve retrieval accuracy and to optimize the cost–benefit ratio of future satellite missions for the remote sensing of greenhouse gases. To address this question, we degrade GOSAT measurements with a spectral resolution of ≈ 0.24 cm^(−1) step by step to a resolution of 1.5 cm^(−1). We examine the results by comparing relative differences at various resolutions, by referring the results to reference values from the Total Carbon Column Observing Network (TCCON), and by calculating and inverting synthetic spectra for which the true CO_2 and CH_4 columns are known. The main impacts of degrading the spectral resolution are reproduced for all approaches based on GOSAT measurements; pure forward model errors identified with simulated measurements are much smaller. For GOSAT spectra, the most notable effect on CO_2 retrieval accuracy is the increase of the standard deviation of retrieval errors from 0.7 to 1.0% when the spectral resolution is reduced by a factor of six. The retrieval biases against atmospheric water abundance and air mass become stronger with decreasing resolution. The error scatter increase for CH_4 columns is less pronounced. The selective degradation of single spectral windows demonstrates that the retrieval accuracy of CO_2 and CH_4 is dominated by the spectral range where the absorption lines of the target molecule are located. For both GOSAT and synthetic measurements, retrieval accuracy decreases with lower spectral resolution for a given signal-to-noise ratio, suggesting increasing interference errors.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.5194/amt-7-1105-2014DOIArticle
http://www.atmos-meas-tech.net/7/1105/2014/amt-7-1105-2014.htmlPublisherArticle
ORCID:
AuthorORCID
Wunch, D.0000-0002-4924-0377
Wennberg, P. O.0000-0002-6126-3854
Alternate Title:The impact of spectral resolution on satellite retrieval accuracy of CO2 and CH4
Additional Information:© Author(s) 2014. This work is distributed under the Creative Commons Attribution 3.0 License. Received: 15 November 2013; Published in Atmos. Meas. Tech. Discuss.: 4 December 2013; Revised: 26 February 2014; Accepted: 13 March 2014; Published: 29 April 2014. The first author was supported by ESA under ESA contract number 4000105676/12/NL/AF. S. Guerlet acknowledges funding from ESA’s Climate Change Initiative on greenhouse gases and the European Commission’s Seventh Framework Programme under grant agreement 218793. A. Butz is supported by Deutsche Forschungsgemeinschaft (DFG) through the Emmy Noether Programme, grant BU2599/1-1 (RemoTeC). US funding for TCCON comes from NASA’s Terrestrial Ecology Program, grant number NNX11AG01G, the Orbiting Carbon Observatory Program, the Atmospheric CO2 Observations from Space (ACOS) Program and the DOE/ARM Program. The Darwin TCCON site was built at Caltech with funding from the OCO project, and is operated by the University of Wollongong, with travel funds for maintenance and equipment costs funded by the OCO-2 project. We acknowledge funding to support Darwin and Wollongong from the Australian Research Council, Projects LE0668470, DP0879468, DP110103118 and LP0562346. The University of Bremen acknowledges financial support of the Białystok and Orléans TCCON sites from the Senate of Bremen and EU projects IMECC, GEOmon, InGOS, and ICOS-INWIRE, as well as maintenance and logistical work provided by AeroMeteo Service (Białystok) and the RAMCES team at LSCE (Gif-sur-Yvette, France) and additional operational funding from the National Institute for Environmental Studies. ECMWF ERA Interim analyses are provided through http://data-portal.ecmwf.int/data/d/interimdaily/. TM4 modelled CH4 and CO concentration fields have been made available through J. F. Meirink, Royal Netherlands Meteorological Institute (KNMI). Edited by: A. Lambert
Funders:
Funding AgencyGrant Number
European Space Agency (ESA)4000105676/12/NL/AF
European Research Council (ERC)218793
Deutsche Forschungsgemeinschaft (DFG)BU2599/1-1
Australian Research CouncilLE0668470
Australian Research CouncilDP0879468
Australian Research CouncilDP110103118
Australian Research CouncilLP0562346
National Institute for Environmental StudiesUNSPECIFIED
NASANNX11AG01G
Department of Energy (DOE)UNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20140530-105533786
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140530-105533786
Official Citation:Galli, A., Guerlet, S., Butz, A., Aben, I., Suto, H., Kuze, A., Deutscher, N. M., Notholt, J., Wunch, D., Wennberg, P. O., Griffith, D. W. T., Hasekamp, O., and Landgraf, J.: The impact of spectral resolution on satellite retrieval accuracy of CO2 and CH4, Atmos. Meas. Tech., 7, 1105-1119, doi:10.5194/amt-7-1105-2014, 2014.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46005
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:30 May 2014 19:42
Last Modified:03 Oct 2019 06:39

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