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Emissions and topographic effects on column CO_2 (XCO_2) variations, with a focus on the Southern California Megacity

Hedelius, Jacob K. and Feng, Sha and Roehl, Coleen M. and Wunch, Debra and Hillyard, Patrick W. and Podolske, James R. and Iraci, Laura T. and Patarasuk, Risa and Rao, Preeti and O'Keeffe, Darragh and Gurney, Kevin R. and Lauvaux, Thomas and Wennberg, Paul O. (2017) Emissions and topographic effects on column CO_2 (XCO_2) variations, with a focus on the Southern California Megacity. Journal of Geophysical Research. Atmospheres, 122 (13). pp. 7200-7215. ISSN 2169-897X. http://resolver.caltech.edu/CaltechAUTHORS:20170731-111148406

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Abstract

Within the California South Coast Air Basin (SoCAB), X_(CO)_2 varies significantly due to atmospheric dynamics and the nonuniform distribution of sources. X_(CO)_2 measurements within the basin have seasonal variation compared to the “background” due primarily to dynamics, or the origins of air masses coming into the basin. We observe basin-background differences that are in close agreement for three observing systems: Total Carbon Column Observing Network (TCCON) 2.3 ± 1.2 ppm, Orbiting Carbon Observatory-2 (OCO-2) 2.4 ± 1.5 ppm, and Greenhouse gases Observing Satellite 2.4 ± 1.6 ppm (errors are 1σ). We further observe persistent significant differences (∼0.9 ppm) in X_(CO)_2 between two TCCON sites located only 9 km apart within the SoCAB. We estimate that 20% (±1σ confidence interval (CI): 0%, 58%) of the variance is explained by a difference in elevation using a full physics and emissions model and 36% (±1σ CI: 10%, 101%) using a simple, fixed mixed layer model. This effect arises in the presence of a sharp gradient in any species (here we focus on CO_2) between the mixed layer (ML) and free troposphere. Column differences between nearby locations arise when the change in elevation is greater than the change in ML height. This affects the fraction of atmosphere that is in the ML above each site. We show that such topographic effects produce significant variation in X_(CO)_2 across the SoCAB as well.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1002/2017JD026455DOIArticle
http://onlinelibrary.wiley.com/wol1/doi/10.1002/2017JD026455/abstractPublisherArticle
http://onlinelibrary.wiley.com/wol1/doi/10.1002/2017JD026455/suppinfoRelated ItemSupporting Information
ORCID:
AuthorORCID
Hedelius, Jacob K.0000-0003-2025-7519
Roehl, Coleen M.0000-0001-5383-8462
Wunch, Debra0000-0002-4924-0377
Iraci, Laura T.0000-0002-2859-5259
Patarasuk, Risa0000-0002-3961-4662
Rao, Preeti0000-0002-5549-0583
Gurney, Kevin R.0000-0001-9218-7164
Wennberg, Paul O.0000-0002-6126-3854
Additional Information:© 2017 American Geophysical Union. Issue online: 25 Jul 2017; Version of Record online: 11 Jul 2017; Accepted manuscript online: 6 Jun 2017; Manuscript Accepted: 5 Jun 2017; Manuscript Revised: 30 May 2017; Manuscript Received: 4 Jan 2017. ASTER GDEM is a product of METI and NASA. We gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model (http://www.ready.noaa.gov) used in this publication. OCO-2 lite files were produced by the OCO-2 project at the Jet Propulsion Laboratory, California Institute of Technology, and obtained from the OCO-2 data archive maintained at the NASA Goddard Earth Science Data and Information Services Center. Nightlight products were obtained from the Earth Observation Group, NOAA National Geophysical Data Center and are based on Suomi NPP satellite observations (http://ngdc.noaa.gov/eog/viirs/). TCCON data are available from the CDIAC and will also be available through the Caltech library archive by 2018 [Iraci et al., 2014; Wennberg et al., 2014b, 2014a]. Model data are available upon request. We thank Chris O'Dell and the ACOS team for early access to the GOSAT-ACOS v7.3 data. We thank Camille Viatte, Eric Kort, and Kristal Verhulst for helpful discussions. The authors thank funding sources. This work is supported in part by the W. M. Keck Institute for Space Studies. The authors gratefully acknowledge TCCON funding from the NASA Carbon Cycle Science program (grant numbers NNX14AI60G and NNX17AE15G), and the Jet Propulsion Laboratory OCO-2 program (grant 1517180). Kevin R. Gurney thanks NIST grant 70NANB14H321. The authors also wish to thank the OCO-2 Science Team grant NNX15AI42G and NASA EVS ACT-America grant NNX15AG76G. The authors thank the referees for their comments. This paper is edited by A. Steiner and reviewed by two anonymous referees.
Group:Keck Institute for Space Studies
Funders:
Funding AgencyGrant Number
Keck Institute for Space Studies (KISS)UNSPECIFIED
NASANNX14AI60G
NASANNX17AE15G
JPL1517180
National Institute of Standards and Technology (NIST)70NANB14H321
NASANNX15AI42G
NASANNX15AG76G
Record Number:CaltechAUTHORS:20170731-111148406
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20170731-111148406
Official Citation:Hedelius, J. K., et al. (2017), Emissions and topographic effects on column CO2 ( inline image) variations, with a focus on the Southern California Megacity, J. Geophys. Res. Atmos., 122, 7200–7215, doi:10.1002/2017JD026455.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79597
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:01 Aug 2017 19:40
Last Modified:02 Feb 2018 17:33

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