Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 3843-3863, 2016
https://doi.org/10.5194/acp-16-3843-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
22 Mar 2016
Toward consistency between trends in bottom-up CO2 emissions and top-down atmospheric measurements in the Los Angeles megacity
Sally Newman1, Xiaomei Xu2, Kevin R. Gurney3, Ying Kuang Hsu4, King Fai Li5, Xun Jiang6, Ralph Keeling7, Sha Feng8,a, Darragh O'Keefe3, Risa Patarasuk3, Kam Weng Wong8, Preeti Rao8, Marc L. Fischer9, and Yuk L. Yung1 1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
2Department of Earth System Science, University of California, Irvine, CA 92697, USA
3School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
4Monitoring and Laboratory Division, Air Resources Board, Sacramento, CA 95811, USA
5Department of Applied Mathematics, University of Washington, Seattle, WA 98195, USA
6Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX 77004, USA
7Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92037, USA
8Earth Atmospheric Science, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
9Environmental Energy Area, E. O. Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
anow at: Department of Meteorology, Pennsylvania State University, University Park, PA 16802, USA
Abstract. Large urban emissions of greenhouse gases result in large atmospheric enhancements relative to background that are easily measured. Using CO2 mole fractions and Δ14C and δ13C values of CO2 in the Los Angeles megacity observed in inland Pasadena (2006–2013) and coastal Palos Verdes peninsula (autumn 2009–2013), we have determined time series for CO2 contributions from fossil fuel combustion (Cff) for both sites and broken those down into contributions from petroleum and/or gasoline and natural gas burning for Pasadena. We find a 10 % reduction in Pasadena Cff during the Great Recession of 2008–2010, which is consistent with the bottom-up inventory determined by the California Air Resources Board. The isotopic variations and total atmospheric CO2 from our observations are used to infer seasonality of natural gas and petroleum combustion. The trend of CO2 contributions to the atmosphere from natural gas combustion is out of phase with the seasonal cycle of total natural gas combustion seasonal patterns in bottom-up inventories but is consistent with the seasonality of natural gas usage by the area's electricity generating power plants. For petroleum, the inferred seasonality of CO2 contributions from burning petroleum is delayed by several months relative to usage indicated by statewide gasoline taxes. Using the high-resolution Hestia-LA data product to compare Cff from parts of the basin sampled by winds at different times of year, we find that variations in observed fossil fuel CO2 reflect seasonal variations in wind direction. The seasonality of the local CO2 excess from fossil fuel combustion along the coast, on Palos Verdes peninsula, is higher in autumn and winter than spring and summer, almost completely out of phase with that from Pasadena, also because of the annual variations of winds in the region. Variations in fossil fuel CO2 signals are consistent with sampling the bottom-up Hestia-LA fossil CO2 emissions product for sub-city source regions in the LA megacity domain when wind directions are considered.

Citation: Newman, S., Xu, X., Gurney, K. R., Hsu, Y. K., Li, K. F., Jiang, X., Keeling, R., Feng, S., O'Keefe, D., Patarasuk, R., Wong, K. W., Rao, P., Fischer, M. L., and Yung, Y. L.: Toward consistency between trends in bottom-up CO2 emissions and top-down atmospheric measurements in the Los Angeles megacity, Atmos. Chem. Phys., 16, 3843-3863, https://doi.org/10.5194/acp-16-3843-2016, 2016.
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Short summary
Combining 14C and 13C data from the Los Angeles, CA megacity with background data allows source attribution of CO2 emissions among biosphere, natural gas, and gasoline. The 8-year record of CO2 emissions from fossil fuel burning is consistent with "The Great Recession" of 2008–2010. The long-term trend and source attribution are consistent with government inventories. Seasonal patterns agree with the high-resolution Hestia-LA emission data product, when seasonal wind directions are considered.
Combining 14C and 13C data from the Los Angeles, CA megacity with background data allows source...
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