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Estimating nitrous oxide (N₂O) emissions for the Los Angeles Megacity using mountaintop remote sensing observations

Addington, Olivia and Zeng, Zhao-Cheng and Pongetti, Thomas and Shia, Run-Lie and Gurney, Kevin R. and Liang, Jianming and Roest, Geoffrey and He, Liyin and Yung, Yuk L. and Sander, Stanley P. (2021) Estimating nitrous oxide (N₂O) emissions for the Los Angeles Megacity using mountaintop remote sensing observations. Remote Sensing of Environment, 259 . Art. No. 112351. ISSN 0034-4257. doi:10.1016/j.rse.2021.112351.

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Nitrous oxide (N₂O) is an important greenhouse gas contributing both to global radiative forcing and ozone depletion. Though N₂O emissions are largely derived from agricultural activities, urban sources of N₂O also contribute significantly to anthropogenic emissions, but are not well understood and difficult to quantify. This study employs a top-down approach to derive urban N₂O emissions for the Los Angeles megacity using a unique dataset from a mountaintop remote sensing instrument, which has been observing greenhouse gas mixing ratios in LA since 2011. CLARS-FTS observations yield a weighted mean of 15.0 ± 0.1 ppb excess XN₂O above background in the LA basin from 2013 to 2019. Time series of XN₂O_(xs) show a seasonal cycle with a peak-to-peak amplitude of 5.6 ± 2.5 ppb, where greater XN₂O_(xs) values are observed during the winter/spring and minima occur in late summer/early fall. A tracer-tracer ratio method is applied using XN₂O_(xs) and XCO_(2,xs) observations to estimate top-down N₂O emissions for the LA basin during 2013–2018. Estimated monthly emissions range from 6 to 19 Gg N₂O per month and exhibit a similar seasonal cycle to that observed in XN₂O_(xs). Estimated annual emissions fall within the range 124–144 Gg per year for the years 2014–2018. These top-down annual estimates are roughly 3 times the official statewide bottom-up inventory for the same time period, but consistent considering uncertainties with other top-down estimates for the LA basin. The discrepancy between top-down emission estimates and the statewide bottom-up inventory highlights the difficulty in constraining N₂O emissions, especially for an urban environment.

Item Type:Article
Related URLs:
URLURL TypeDescription
https://megacities.jpl.nasa.govRelated ItemNASA Megacities Project
Zeng, Zhao-Cheng0000-0002-0008-6508
Pongetti, Thomas0000-0001-9465-0853
Shia, Run-Lie0000-0003-1911-3120
Gurney, Kevin R.0000-0001-9218-7164
Liang, Jianming0000-0002-4043-6816
He, Liyin0000-0003-4427-1438
Yung, Yuk L.0000-0002-4263-2562
Sander, Stanley P.0000-0003-1424-3620
Alternate Title:Estimating nitrous oxide (N2O) emissions for the Los Angeles Megacity using mountaintop remote sensing observations
Additional Information:© 2021 Elsevier. Received 8 July 2020, Revised 2 February 2021, Accepted 9 February 2021, Available online 1 April 2021. The views expressed in this article are those of the authors and do not necessarily reflect the official opinions of the funding agencies for this work. We thank A. Andrews and E. Dlugokencky for providing NOAA flask measurements at Mt. Wilson Observatory (National Oceanic and Atmospheric Administration, 2019). The CLARS project receives support from the California Air Resources Board. CLARS-FTS data are available from the authors upon request, and part of the data are available from the NASA Megacities Project at A portion of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. O. A. acknowledges support from the Jet Propulsion Laboratory (Maximizing Student Potential in STEM) and from Occidental College (NSF COSMOS). Declaration of Competing Interest. None.
Funding AgencyGrant Number
California Air Resources BoardUNSPECIFIED
Occidental CollegeUNSPECIFIED
Subject Keywords:Nitrous oxide; Urban remote sensing; Los Angeles; Megacity; CLARS
Record Number:CaltechAUTHORS:20210527-093456773
Persistent URL:
Official Citation:Olivia Addington, Zhao-Cheng Zeng, Thomas Pongetti, Run-Lie Shia, Kevin R. Gurney, Jianming Liang, Geoffrey Roest, Liyin He, Yuk L. Yung, Stanley P. Sander, Estimating nitrous oxide (N2O) emissions for the Los Angeles Megacity using mountaintop remote sensing observations, Remote Sensing of Environment, Volume 259, 2021, 112351, ISSN 0034-4257,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109273
Deposited By: George Porter
Deposited On:27 May 2021 21:41
Last Modified:16 Nov 2021 19:35

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