TY - JOUR
T1 - Simulating estimation of California fossil fuel and biosphere carbon dioxide exchanges combining in situ tower and satellite column observations
AU - Fischer, Marc L.
AU - Parazoo, Nicholas
AU - Brophy, Kieran
AU - Cui, Xinguang
AU - Jeong, Seongeun
AU - Liu, Junjie
AU - Keeling, Ralph
AU - Taylor, Thomas E.
AU - Gurney, Kevin
AU - Oda, Tomohiro
AU - Graven, Heather
N1 - Funding Information:
We gratefully acknowledge Jim Collatz and Andrew Jacobson for producing the CASA and Carbon Tracker biosphere CO2 exchanges used in this work and for insightful comments on the manuscript. We also thank John Lin, Christoph Gerbig, Steve Wofsy, Janusz Eluszkiewicz, and Thomas Nehrkorn for making the STILT code publicly available; Krishna Muriki for assistance running the WRF-STILT models on the LBNL-Lawrencium cluster; and two anonymous reviewers for valuable suggestions that improved the paper. All prior CO2 emission models used in this simulation study are available on websites listed in the references. Simulated CO2 signals calculated with Vulcan and CASA biosphere CO2 fluxes for OCO-2 and tower receptors are being made available at the Oak Ridge DAC (https://doi.org/10.3334/ORNLDAAC/1381). This study was supported by the NASA CMS program (NNH13ZDA001N) under U.S. Department of Energy contract DE-AC02-05CH11231.
Publisher Copyright:
© 2017. American Geophysical Union.
PY - 2017
Y1 - 2017
N2 - We report simulation experiments estimating the uncertainties in California regional fossil fuel and biosphere CO2 exchanges that might be obtained by using an atmospheric inverse modeling system driven by the combination of ground-based observations of radiocarbon and total CO2, together with column-mean CO2 observations from NASA’s Orbiting Carbon Observatory (OCO-2). The work includes an initial examination of statistical uncertainties in prior models for CO2 exchange, in radiocarbon-based fossil fuel CO2 measurements, in OCO-2 measurements, and in a regional atmospheric transport modeling system. Using these nominal assumptions for measurement and model uncertainties, we find that flask measurements of radiocarbon and total CO2 at 10 towers can be used to distinguish between different fossil fuel emission data products for major urban regions of California. We then show that the combination of flask and OCO-2 observations yields posterior uncertainties in monthly-mean fossil fuel emissions of ~5-10%, levels likely useful for policy relevant evaluation of bottom-up fossil fuel emission estimates. Similarly, we find that inversions yield uncertainties in monthly biosphere CO2 exchange of ~6%-12%, depending on season, providing useful information on net carbon uptake in California’s forests and agricultural lands. Finally, initial sensitivity analysis suggests that obtaining the above results requires control of systematic biases below approximately 0.5 ppm, placing requirements on accuracy of the atmospheric measurements, background subtraction, and atmospheric transport modeling.
AB - We report simulation experiments estimating the uncertainties in California regional fossil fuel and biosphere CO2 exchanges that might be obtained by using an atmospheric inverse modeling system driven by the combination of ground-based observations of radiocarbon and total CO2, together with column-mean CO2 observations from NASA’s Orbiting Carbon Observatory (OCO-2). The work includes an initial examination of statistical uncertainties in prior models for CO2 exchange, in radiocarbon-based fossil fuel CO2 measurements, in OCO-2 measurements, and in a regional atmospheric transport modeling system. Using these nominal assumptions for measurement and model uncertainties, we find that flask measurements of radiocarbon and total CO2 at 10 towers can be used to distinguish between different fossil fuel emission data products for major urban regions of California. We then show that the combination of flask and OCO-2 observations yields posterior uncertainties in monthly-mean fossil fuel emissions of ~5-10%, levels likely useful for policy relevant evaluation of bottom-up fossil fuel emission estimates. Similarly, we find that inversions yield uncertainties in monthly biosphere CO2 exchange of ~6%-12%, depending on season, providing useful information on net carbon uptake in California’s forests and agricultural lands. Finally, initial sensitivity analysis suggests that obtaining the above results requires control of systematic biases below approximately 0.5 ppm, placing requirements on accuracy of the atmospheric measurements, background subtraction, and atmospheric transport modeling.
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U2 - 10.1002/2016JD025617
DO - 10.1002/2016JD025617
M3 - Article
AN - SCOPUS:85016630169
SN - 0148-0227
VL - 122
SP - 3653
EP - 3671
JO - Journal of Geophysical Research
JF - Journal of Geophysical Research
IS - 6
ER -