Southern California megacity CO_2, CH_4, and CO flux estimates using ground- and space-based remote sensing and a Lagrangian model

Creators: Hedelius, Jacob K.; Liu, Junjie; Oda, Tomohiro; Maksyutov, Shamil; Roehl, Coleen M.; Iraci, Laura T.; Podolske, James R.; Hillyard, Patrick W.; Liang, Jianming; Gurney, Kevin R.; Wunch, Debra; Wennberg, Paul O.

Abstract

We estimate the overall CO_2, CH_4, and CO flux from the South Coast Air Basin using an inversion that couples Total Carbon Column Observing Network (TCCON) and Orbiting Carbon Observatory-2 (OCO-2) observations, with the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and the Open-source Data Inventory for Anthropogenic CO2 (ODIAC). Using TCCON data we estimate the direct net CO_2 flux from the SoCAB to be 104 ± 26 Tg CO_2 yr^(−1) for the study period of July 2013–August 2016. We obtain a slightly higher estimate of 120 ± 30 Tg CO)2 yr^(−1) using OCO-2 data. These CO_2 emission estimates are on the low end of previous work. Our net CH_4 (360 ± 90 Gg CH_4 yr^(−1)) flux estimate is in agreement with central values from previous top-down studies going back to 2010 (342–440 Gg CH_4 yr^(−1)). CO emissions are estimated at 487 ± 122 Gg CO yr^(−1), much lower than previous top-down estimates (1440 Gg CO yr^(−1)). Given the decreasing emissions of CO, this finding is not unexpected. We perform sensitivity tests to estimate how much errors in the prior, errors in the covariance, different inversion schemes, or a coarser dynamical model influence the emission estimates. Overall, the uncertainty is estimated to be 25 %, with the largest contribution from the dynamical model. Lessons learned here may help in future inversions of satellite data over urban areas.

Additional Information

© Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Received: 23 May 2018 – Discussion started: 31 May 2018 – Revised: 12 Oct 2018 – Accepted: 30 Oct 2018 – Published: 16 Nov 2018. The authors wish to acknowledge providers of data. OCO-2 lite files were produced by the OCO-2 project at the Jet Propulsion Laboratory, California Institute of Technology. Resources supporting OCO-2 retrievals were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center. Nightlight products were obtained from the Earth Observation Group, NOAA National Geophysical Data Center and are based on Suomi NPP satellite observations. The 0.1∘ methane inventory was produced by Harvard University in collaboration with the EPA. The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport model (http://www.ready.noaa.gov, last access: 12 November 2018) as well as the gridded archived meteorological data used in this publication. We thank Ron Cohen, Nick Parazoo, Anna Karion, and Taylor Jones for helpful discussions. We thank Nasrin Pak for discussions on landfills. This work was financially supported by NASA's OCO-2 project (grant no. NNN12AA01C) and NASA's carbon cycle and ecosystems research program (grant no. NNX14AI60G and NNX17AE15G). Tomohiro Oda is supported by the NASA Carbon Cycle Science program (grant no. NNX14AM76G). The Hestia data product was made possible through support from Purdue University Showalter Trust, the National Aeronautics and Space Administration grant 1491755, and the National Institute of Standards and Technology grants 70NANB14H321 and 70NANB16H264. The authors thank the referees for their comments. Edited by: Robert McLaren. Reviewed by:two anonymous referees. Author contributions. JKH, JuL, and POW were involved in the overall conceptualization, investigation, and methodology development. JKH carried out the formal analysis and visualization and wrote the original draft. POW secured funding and computational resources and provided supervision. TO and SM developed the ODIAC FF inventory and provided instructions on its use. KG and JiL developed the Hestia-LA FF inventory and provided instructions on its use. CMR, LTI, JRP, PWH, DW, and POW provided TCCON data, which involved funding acquisition, site management, data processing, and QA/QC. JKH, JuL, TO, LTI, DW, and POW were involved in revising the paper. The authors declare that they have no conflict of interest. Data availability. TCCON data used in this study (GGG2014: Iraci, et al., 2014; Wennberg et al., 2014) are hosted at the TCCON data archive (https://tccondata.org/, last access: 23 November 2017) and are used in accordance with the Data Use Policy (https://tccon-wiki.caltech.edu/Network_Policy/Data_Use_Policy, last access: 23 November 2017). OCO-2 data (OCO-2 Science Team et al., 2017) are hosted by Goddard Earth Sciences (GES) Data and Information Services Center (DISC) (https://disc.gsfc.nasa.gov/datasets/OCO2_L2_Lite_FP_8r/summary, last access: 2 January 2018). ODIAC2016 data (Oda et al., 2015) are hosted by NIES (http://db.cger.nies.go.jp/dataset/ODIAC/, last access: 30 July 2018). Hestia-LA and Vulcan data can be obtained by contacting Kevin Gurney (Kevin.Gurney@nau.edu). 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/, last access: 16 August 2017). Gridded Harvard–EPA emissions are hosted on the EPA website (https://www.epa.gov/ghgemissions/gridded-2012-methane-emissions, last access: 10 November 2016). NOAA gridded meteorological data are hosted on the NOAA ARL server (https://www.ready.noaa.gov/archives.php, last access 24 October 2017). The CARB regularly publishes emission inventories of various gases. CO inventories are available online (2017: https://www.arb.ca.gov/app/emsinv/2017/emssumcat.php, 2013: https://www.arb.ca.gov/app/emsinv/2013/emssumcat.php, 2009: https://www.arb.ca.gov/app/emsinv/fcemssumcat2009.php, last access: 12 November 2018), as are CH4 inventories (2017: https://www.arb.ca.gov/app/ghg/2000_2015/ghg_sector_data.php, 2013: https://www.arb.ca.gov/app/ghg/2000_2011/ghg_sector_data.php, 2009: https://www.arb.ca.gov/app/ghg/2000_2006/ghg_sector.php, last access: 12 November 2018).

Attached Files

Published - acp-18-16271-2018.pdf

Files

acp-18-16271-2018.pdf

Files (4.9 MB)

Name	Size	Download all
acp-18-16271-2018.pdf md5:7706538173fe56e9e47a6025d147ba5f	4.9 MB	Preview Download

Additional details

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes