Reducing errors in aircraft atmospheric inversion estimates of point-source emissions: the Aliso Canyon natural gas leak as a natural tracer experiment
Urban greenhouse gas (GHG) flux estimation with atmospheric measurements and modeling, i.e. the ‘top-down’ approach, can potentially support GHG emission reduction policies by assessing trends in surface fluxes and detecting anomalies from bottom-up inventories. Aircraft-collected GHG observations a...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2018-01-01
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| Series: | Environmental Research Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1748-9326/aab049 |
| _version_ | 1797748249467027456 |
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| author | S M Gourdji V Yadav A Karion K L Mueller S Conley T Ryerson T Nehrkorn E A Kort |
| author_facet | S M Gourdji V Yadav A Karion K L Mueller S Conley T Ryerson T Nehrkorn E A Kort |
| author_sort | S M Gourdji |
| collection | DOAJ |
| description | Urban greenhouse gas (GHG) flux estimation with atmospheric measurements and modeling, i.e. the ‘top-down’ approach, can potentially support GHG emission reduction policies by assessing trends in surface fluxes and detecting anomalies from bottom-up inventories. Aircraft-collected GHG observations also have the potential to help quantify point-source emissions that may not be adequately sampled by fixed surface tower-based atmospheric observing systems. Here, we estimate CH _4 emissions from a known point source, the Aliso Canyon natural gas leak in Los Angeles, CA from October 2015–February 2016, using atmospheric inverse models with airborne CH _4 observations from twelve flights ≈4 km downwind of the leak and surface sensitivities from a mesoscale atmospheric transport model. This leak event has been well-quantified previously using various methods by the California Air Resources Board, thereby providing high confidence in the mass-balance leak rate estimates of (Conley et al 2016 ), used here for comparison to inversion results. Inversions with an optimal setup are shown to provide estimates of the leak magnitude, on average, within a third of the mass balance values, with remaining errors in estimated leak rates predominantly explained by modeled wind speed errors of up to 10 m s ^−1 , quantified by comparing airborne meteorological observations with modeled values along the flight track. An inversion setup using scaled observational wind speed errors in the model-data mismatch covariance matrix is shown to significantly reduce the influence of transport model errors on spatial patterns and estimated leak rates from the inversions. In sum, this study takes advantage of a natural tracer release experiment (i.e. the Aliso Canyon natural gas leak) to identify effective approaches for reducing the influence of transport model error on atmospheric inversions of point-source emissions, while suggesting future potential for integrating surface tower and aircraft atmospheric GHG observations in top-down urban emission monitoring systems. |
| first_indexed | 2024-03-12T16:03:13Z |
| format | Article |
| id | doaj.art-042769e520194552818da3caec977115 |
| institution | Directory Open Access Journal |
| issn | 1748-9326 |
| language | English |
| last_indexed | 2024-03-12T16:03:13Z |
| publishDate | 2018-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Environmental Research Letters |
| spelling | doaj.art-042769e520194552818da3caec9771152023-08-09T14:31:38ZengIOP PublishingEnvironmental Research Letters1748-93262018-01-0113404500310.1088/1748-9326/aab049Reducing errors in aircraft atmospheric inversion estimates of point-source emissions: the Aliso Canyon natural gas leak as a natural tracer experimentS M Gourdji0https://orcid.org/0000-0002-0309-9187V Yadav1A Karion2K L Mueller3S Conley4T Ryerson5T Nehrkorn6E A Kort7National Institute of Standards and Technology (NIST) ; Gaithersburg, MD, United States of America; University of Michigan , Climate and Space Sciences and Engineering, Ann Arbor, MI, United States of America; Author to whom any correspondence should be addressed.NASA Jet Propulsion Laboratory , Pasadena, CA, United States of AmericaNational Institute of Standards and Technology (NIST) ; Gaithersburg, MD, United States of AmericaNational Institute of Standards and Technology (NIST) ; Gaithersburg, MD, United States of America; University of Michigan , Climate and Space Sciences and Engineering, Ann Arbor, MI, United States of AmericaScientific Aviation , Boulder, CO, United States of AmericaNOAA Earth Systems Research Laboratory , Boulder, CO, United States of AmericaAtmospheric and Environmental Research , Lexington, MA, United States of AmericaUniversity of Michigan , Climate and Space Sciences and Engineering, Ann Arbor, MI, United States of AmericaUrban greenhouse gas (GHG) flux estimation with atmospheric measurements and modeling, i.e. the ‘top-down’ approach, can potentially support GHG emission reduction policies by assessing trends in surface fluxes and detecting anomalies from bottom-up inventories. Aircraft-collected GHG observations also have the potential to help quantify point-source emissions that may not be adequately sampled by fixed surface tower-based atmospheric observing systems. Here, we estimate CH _4 emissions from a known point source, the Aliso Canyon natural gas leak in Los Angeles, CA from October 2015–February 2016, using atmospheric inverse models with airborne CH _4 observations from twelve flights ≈4 km downwind of the leak and surface sensitivities from a mesoscale atmospheric transport model. This leak event has been well-quantified previously using various methods by the California Air Resources Board, thereby providing high confidence in the mass-balance leak rate estimates of (Conley et al 2016 ), used here for comparison to inversion results. Inversions with an optimal setup are shown to provide estimates of the leak magnitude, on average, within a third of the mass balance values, with remaining errors in estimated leak rates predominantly explained by modeled wind speed errors of up to 10 m s ^−1 , quantified by comparing airborne meteorological observations with modeled values along the flight track. An inversion setup using scaled observational wind speed errors in the model-data mismatch covariance matrix is shown to significantly reduce the influence of transport model errors on spatial patterns and estimated leak rates from the inversions. In sum, this study takes advantage of a natural tracer release experiment (i.e. the Aliso Canyon natural gas leak) to identify effective approaches for reducing the influence of transport model error on atmospheric inversions of point-source emissions, while suggesting future potential for integrating surface tower and aircraft atmospheric GHG observations in top-down urban emission monitoring systems.https://doi.org/10.1088/1748-9326/aab049urban greenhouse gas emissionsinverse modelingAliso Canyon natural gas leakaircraft observationstransport model error |
| spellingShingle | S M Gourdji V Yadav A Karion K L Mueller S Conley T Ryerson T Nehrkorn E A Kort Reducing errors in aircraft atmospheric inversion estimates of point-source emissions: the Aliso Canyon natural gas leak as a natural tracer experiment Environmental Research Letters urban greenhouse gas emissions inverse modeling Aliso Canyon natural gas leak aircraft observations transport model error |
| title | Reducing errors in aircraft atmospheric inversion estimates of point-source emissions: the Aliso Canyon natural gas leak as a natural tracer experiment |
| title_full | Reducing errors in aircraft atmospheric inversion estimates of point-source emissions: the Aliso Canyon natural gas leak as a natural tracer experiment |
| title_fullStr | Reducing errors in aircraft atmospheric inversion estimates of point-source emissions: the Aliso Canyon natural gas leak as a natural tracer experiment |
| title_full_unstemmed | Reducing errors in aircraft atmospheric inversion estimates of point-source emissions: the Aliso Canyon natural gas leak as a natural tracer experiment |
| title_short | Reducing errors in aircraft atmospheric inversion estimates of point-source emissions: the Aliso Canyon natural gas leak as a natural tracer experiment |
| title_sort | reducing errors in aircraft atmospheric inversion estimates of point source emissions the aliso canyon natural gas leak as a natural tracer experiment |
| topic | urban greenhouse gas emissions inverse modeling Aliso Canyon natural gas leak aircraft observations transport model error |
| url | https://doi.org/10.1088/1748-9326/aab049 |
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