TY - JOUR
T1 - Southern California megacity CO2, CH4, and CO flux estimates using ground-and space-based remote sensing and a Lagrangian model
AU - Hedelius, Jacob K.
AU - Liu, Junjie
AU - Oda, Tomohiro
AU - Maksyutov, Shamil
AU - Roehl, Coleen M.
AU - Iraci, Laura T.
AU - Podolske, James R.
AU - Hillyard, Patrick W.
AU - Liang, Jianming
AU - Gurney, Kevin R.
AU - Wunch, Debra
AU - Wennberg, Paul O.
N1 - Funding Information:
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.
Publisher Copyright:
© 2018 The Author(s).
PY - 2018/11/16
Y1 - 2018/11/16
N2 - We estimate the overall CO2, CH4, 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 CO2 flux from the SoCAB to be 104 ± 26 Tg CO2 yr-1 for the study period of July 2013-August 2016. We obtain a slightly higher estimate of 120 ± 30 Tg CO2 yr-1 using OCO-2 data. These CO2 emission estimates are on the low end of previous work. Our net CH4 (360 ± 90 Gg CH4 yr-1) flux estimate is in agreement with central values from previous top-down studies going back to 2010 (342-440 Gg CH4 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.
AB - We estimate the overall CO2, CH4, 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 CO2 flux from the SoCAB to be 104 ± 26 Tg CO2 yr-1 for the study period of July 2013-August 2016. We obtain a slightly higher estimate of 120 ± 30 Tg CO2 yr-1 using OCO-2 data. These CO2 emission estimates are on the low end of previous work. Our net CH4 (360 ± 90 Gg CH4 yr-1) flux estimate is in agreement with central values from previous top-down studies going back to 2010 (342-440 Gg CH4 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.
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U2 - 10.5194/acp-18-16271-2018
DO - 10.5194/acp-18-16271-2018
M3 - Article
AN - SCOPUS:85056898562
SN - 1680-7316
VL - 18
SP - 16271
EP - 16291
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
IS - 22
ER -