Potential of 14C-based versus ∆CO-based ∆ffCO2 observations to estimate urban fossil fuel CO2(ffCO2) emissions

• Verfasst von: Maier, Fabian [VerfasserIn]
• Verfasst von: Rödenbeck, Christian [VerfasserIn]
• Verfasst von: Levin, Ingeborg [VerfasserIn]
• Verfasst von: Gerbig, Christoph [VerfasserIn]
• Verfasst von: Gachkivskyi, Maksym [VerfasserIn]
• Verfasst von: Hammer, Samuel [VerfasserIn]
• Titel: Potential of 14C-based versus ∆CO-based ∆ffCO2 observations to estimate urban fossil fuel CO2(ffCO2) emissions
• Verf.angabe: Fabian Manuel Maier, Christian Rödenbeck, Ingeborg Levin, Christoph Gerbig, Maksym Gachkivskyi, and Samuel Hammer
• E-Jahr: 2023
• Jahr: 3 July 2023
• Umfang: 30 S.
• Fussnoten: Im Titel ist die Zahl 14 hochgestellt, 2 jeweils tiefgestellt ; Gesehen am 05.02.2024
• Titel Quelle: Enthalten in: EGUsphere
• Ort Quelle: Göttingen : Copernicus GmbH, 2022
• Jahr Quelle: 2023
• Band/Heft Quelle: (2023), Artikel-ID 1239, Seite 1-30
• DOI: doi:10.5194/egusphere-2023-1239
• Datenträger: Online-Ressource
• Sprache: eng
• Bibliogr. Hinweis: Forschungsdaten: Maier, Fabian, 1993 - : 14C-based ΔffCO2 estimates for Heidelberg and OPE and input data for the Rhine Valley ffCO2 inversion (2019-2020)
• K10plus-PPN: 1880008858

Abstract

<p><strong class="journal-contentHeaderColor">Abstract.</strong> Atmospheric transport inversions are a powerful tool for independently estimating surface CO₂ fluxes from atmospheric CO₂ concentration measurements. However, additional tracers are needed to separate the fossil fuel CO₂ (ffCO₂) emissions from natural CO₂ fluxes. In this study we focus on radiocarbon (¹⁴C), the most direct tracer for ffCO₂, and the continuously measured surrogate tracer carbon monoxide (CO), which is co-emitted with ffCO₂ during incomplete combustion. In the companion paper by Maier et al. (2023a) we determined for the urban Heidelberg observation site in Southwestern Germany discrete ¹⁴C-based and continuous ∆CO-based estimates of the ffCO₂ excess concentration (∆ffCO₂) compared to a clean-air reference. Here, we use the CarboScope inversion framework adapted for the urban domain around Heidelberg to assess the potential of both types of ∆ffCO₂ observations to investigate ffCO₂ emissions and their seasonal cycle. We find that discrete ¹⁴C-based ∆ffCO₂ observations from almost 100 afternoon flask samples collected in the two years 2019 and 2020 are not well suited for estimating robust ffCO₂ emissions in the main footprint of this urban area with a very heterogeneous distribution of sources including several point sources. The benefit of the continuous ∆CO-based ∆ffCO₂ estimates is that they can be averaged to reduce the impact of individual hours with an inadequate model performance. We show that the weekly averaged ∆CO-based ∆ffCO₂ observations allow for a robust reconstruction of the seasonal cycle of the area source ffCO₂ emissions from temporally flat a-priori emissions. In particular, the distinct COVID-19 signal with a steep drop in emissions in spring 2020 is clearly present in these data-driven a-posteriori results. Moreover, our top-down results show a shift in the seasonality of the area source ffCO₂ emissions around Heidelberg in 2019 compared to the bottom-up estimates from TNO. This highlights the huge potential of ∆CO-based ∆ffCO₂ to verify bottom-up ffCO₂ emissions at urban stations if the ∆CO / ∆ffCO₂ ratios can be determined without biases.</p>