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CH_4 retrievals from space-based solar backscatter measurements: Performance evaluation against simulated aerosol and cirrus loaded scenes

Butz, A. and Hasekamp, O. P. and Frankenberg, C. and Vidot, J. and Aben, I. (2010) CH_4 retrievals from space-based solar backscatter measurements: Performance evaluation against simulated aerosol and cirrus loaded scenes. Journal of Geophysical Research. Atmospheres, 115 (D24). Art. No. D24302. ISSN 2169-897X. http://resolver.caltech.edu/CaltechAUTHORS:20150511-114900532

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Abstract

Monitoring of atmospheric methane (CH_4) concentrations from space-based instruments such as the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) and the Greenhouse Gases Observing Satellite (GOSAT) relies on observations of sunlight backscattered to space by the Earth's surface and atmosphere. Retrieval biases occur due to unaccounted scattering effects by aerosols and thin cirrus that modify the lightpath. Here, we evaluate the accuracy of two retrieval methods that aim at minimizing such scattering induced errors. The lightpath “proxy” method, applicable to SCIAMACHY and GOSAT, retrieves CH4 and carbon dioxide (CO_2) simultaneously and uses CO_2 as a proxy for lightpath modification. The “physics-based” method, which we propose for GOSAT, aims at simultaneously retrieving CH_4 concentrations and scattering properties of the atmosphere. We evaluate performance of the methods against a trial ensemble of simulated aerosol and cirrus loaded scenes. More than 80% of the trials yield residual scattering induced CH_4 errors below 0.6% and 0.8% for the proxy and the physics-based approach, respectively. Very few cases result in errors greater than 2% for both methods. Advantages of the proxy approach are efficient and robust performance yielding more useful retrievals than the physics-based method which reveals some nonconvergent cases. The major disadvantage of the proxy method is the uncertainty of the proxy CO_2 concentration contributing to the overall error budget. Residual errors generally correlate with particle and surface properties and thus might impact inverse modeling of CH_4 sources and sinks.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1029/2010JD014514DOIArticle
http://onlinelibrary.wiley.com/doi/10.1029/2010JD014514/abstractPublisherArticle
http://onlinelibrary.wiley.com/doi/10.1029/2010JD014514/suppinfoPublisherSupporting Information
ORCID:
AuthorORCID
Frankenberg, C.0000-0002-0546-5857
Additional Information:© 2010 American Geophysical Union. Received 20 May 2010; Revised 26 July 2010; Accepted 16 September 2010; Published 16 December 2010. Part of this research was supported by the Dutch User Support Programme 2001‐2005 under project GO‐2005/064. Part of the research leading to these results has received funding from the European Union’s Seventh Framework Programme (FP7/2007‐2013) under grant agreement 218793. The cirrus cloud model is a courtesy of the Royal Netherlands Meteorological Institute (KNMI) through Wouter Knap. ECHAM5‐HAM model output is provided by Gerrit de Leeuw, Finnish Meteorological Institute (FMI). MODIS LAND data are distributed by the Land Processes Distributed Active Archive Center (LP DAAC), located at the U.S. Geological Survey (USGS) Earth Resources Observation and Science Center (EROS) http://LPDAAC.usgs.gov. MODIS Atmosphere data are distributed through http://modis-atmos.gsfc.nasa.gov/index.html. We thank the ICARE Data and Services Center (http://www.icare.univ‐lille.fr) for providing access and assistance to the CALIOP data used in this study. CarbonTracker results are provided by NOAA ESRL, Boulder, Colorado, USA from the Web site at http://carbontracker.noaa.gov. TM4 modeled CH4 concentration fields have been made available through Jan Fokke Meirink, Royal Netherlands Meteorological Institute (KNMI).
Funders:
Funding AgencyGrant Number
Dutch User Support Programme 2001-2005GO‐2005/064
European Research Council (ERC)218793
Subject Keywords:atmospheric methane; remote sensing; radiative transfer
Record Number:CaltechAUTHORS:20150511-114900532
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150511-114900532
Official Citation:Butz, A., Hasekamp, O. P., Frankenberg, C., Vidot, J., & Aben, I. (2010). CH4 retrievals from space-based solar backscatter measurements: Performance evaluation against simulated aerosol and cirrus loaded scenes. Journal of Geophysical Research: Atmospheres, 115(D24), D24302. doi: 10.1029/2010jd014514
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57415
Collection:CaltechAUTHORS
Deposited By: Joanne McCole
Deposited On:11 May 2015 21:26
Last Modified:06 Feb 2017 23:11

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