Estimation of continuous anthropogenic CO2: model-based evaluation of CO2, CO, δ13C(CO2) and Δ14C(CO2) tracer methods
Item
Title (Dublin Core)
Estimation of continuous anthropogenic CO2: model-based evaluation of CO2, CO, δ13C(CO2) and Δ14C(CO2) tracer methods
Description (Dublin Core)
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.
Creator (Dublin Core)
Vardag, S. N.
Gerbig, C.
Janssens-Maenhout, G.
Levin, I.
Date (Dublin Core)
2018-09-07
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-15-12705-2015
https://acp.copernicus.org/articles/15/12705/2015/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
