Estimation of continuous anthropogenic CO2: model-based evaluation of CO2, CO, δ13C(CO2) and Δ14C(CO2) tracer methods
We investigate different methods for estimating anthropogenic CO<sub>2</sub> using modeled continuous atmospheric concentrations of CO<sub>2</sub> alone, as well as CO<sub>2</sub> in combination with the surrogate tracers CO, δ<sup>13</sup>C(...
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| Main Authors: | , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
16 Nov 2015
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| In: |
Atmospheric chemistry and physics. Discussions
Year: 2015, Volume: 15, Issue: 22, Pages: 12705-12729 |
| ISSN: | 1680-7375 |
| DOI: | https://doi.org/10.5194/acp-15-12705-2015 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/https://doi.org/10.5194/acp-15-12705-2015 Verlag, lizenzpflichtig, Volltext: https://acp.copernicus.org/preprints/15/20181/2015/acpd-15-20181-2015.pdf Verlag, lizenzpflichtig, Volltext: www.atmos-chem-phys-discuss.net/15/20181/2015/ 
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| Author Notes: | S.N. Vardag, C. Gerbig, G. Janssens-Maenhout, and I. Levin |
| Summary: | We investigate different methods for estimating anthropogenic CO<sub>2</sub> using modeled continuous atmospheric concentrations of CO<sub>2</sub> alone, as well as CO<sub>2</sub> in combination with the surrogate tracers CO, δ<sup>13</sup>C(CO<sub>2</sub>) and Δ<sup>14</sup>C(CO<sub>2</sub>). These methods are applied at three hypothetical stations representing rural, urban and polluted conditions. We find that, independent of the tracer used, an observation-based estimate of continuous anthropogenic CO<sub>2</sub> is not yet feasible at rural measurement sites due to the low signal-to-noise ratio of anthropogenic CO<sub>2</sub> estimates at such settings. The tracers δ<sup>13</sup>C(CO<sub>2</sub>) and CO provide an accurate possibility to determine anthropogenic CO<sub>2</sub> continuously, only if all CO<sub>2</sub> sources in the catchment area are well characterized or calibrated with respect to their isotopic signature and CO to anthropogenic CO<sub>2</sub> ratio. We test different calibration strategies for the mean isotopic signature and CO to CO<sub>2</sub> ratio using precise Δ<sup>14</sup>C(CO<sub>2</sub>) measurements on monthly integrated as well as on grab samples. For δ<sup>13</sup>C(CO<sub>2</sub>), a calibration with annually averaged <sup>14</sup>C(CO<sub>2</sub>) grab samples is most promising, since integrated sampling introduces large biases into anthropogenic CO<sub>2</sub> estimates. For CO, these biases are smaller. The precision of continuous anthropogenic CO<sub>2</sub> determination using δ<sup>13</sup>C(CO<sub>2</sub>) depends on measurement precision of δ<sup>13</sup>C(CO<sub>2</sub>) and CO<sub>2</sub>, while the CO method is mainly limited by the variation in natural CO sources and sinks. At present, continuous anthropogenic CO<sub>2</sub> could be determined using the tracers δ<sup>13</sup>C(CO<sub>2</sub>) and/or CO with a precision of about 30 %, a mean bias of about 10 % and without significant diurnal discrepancies. Hypothetical future measurements of continuous Δ<sup>14</sup>C(CO<sub>2</sub>) with a precision of 5 ‰ are promising for anthropogenic CO<sub>2</sub> determination (precision ca. 10-20 %) but are not yet available. The investigated tracer-based approaches open the door to improving, validating and reducing biases of highly resolved emission inventories using atmospheric observation and regional modeling.</p> |
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| Item Description: | Im Zusatz zum Titel ist 13 hochgestellt und 14 tiefgestellt Im Titel ist 2 bei CO2 tiefgestellt Gesehen am 08.07.2020 |
| Physical Description: | Online Resource |
| ISSN: | 1680-7375 |
| DOI: | https://doi.org/10.5194/acp-15-12705-2015 |