scholarly journals Independent evaluation of point source fossil fuel CO2 emissions to better than 10%

2016 ◽  
Vol 113 (37) ◽  
pp. 10287-10291 ◽  
Author(s):  
Jocelyn Christine Turnbull ◽  
Elizabeth D. Keller ◽  
Margaret W. Norris ◽  
Rachael M. Wiltshire
Keyword(s):  
Point Source ◽  
Power Plants ◽  
Fossil Fuel ◽  
Transport Model ◽  
Sodium Hydroxide Solution ◽  
Time Integration ◽  
Emission Rates ◽  
Independent Evaluation ◽  
Atmospheric Observations ◽  
Better Than

Independent estimates of fossil fuel CO2 (CO2ff) emissions are key to ensuring that emission reductions and regulations are effective and provide needed transparency and trust. Point source emissions are a key target because a small number of power plants represent a large portion of total global emissions. Currently, emission rates are known only from self-reported data. Atmospheric observations have the potential to meet the need for independent evaluation, but useful results from this method have been elusive, due to challenges in distinguishing CO2ff emissions from the large and varying CO2 background and in relating atmospheric observations to emission flux rates with high accuracy. Here we use time-integrated observations of the radiocarbon content of CO2 (14CO2) to quantify the recently added CO2ff mole fraction at surface sites surrounding a point source. We demonstrate that both fast-growing plant material (grass) and CO2 collected by absorption into sodium hydroxide solution provide excellent time-integrated records of atmospheric 14CO2. These time-integrated samples allow us to evaluate emissions over a period of days to weeks with only a modest number of measurements. Applying the same time integration in an atmospheric transport model eliminates the need to resolve highly variable short-term turbulence. Together these techniques allow us to independently evaluate point source CO2ff emission rates from atmospheric observations with uncertainties of better than 10%. This uncertainty represents an improvement by a factor of 2 over current bottom-up inventory estimates and previous atmospheric observation estimates and allows reliable independent evaluation of emissions.

scholarly journals Global emissions of HFC-143a (CH<sub>3</sub>CF<sub>3</sub>) and HFC-32 (CH<sub>2</sub>F<sub>2</sub>) from in situ and air archive atmospheric observations

2014 ◽  
Vol 14 (17) ◽  
pp. 9249-9258 ◽  
Author(s):  
S. O'Doherty ◽  
M. Rigby ◽  
J. Mühle ◽  
D. J. Ivy ◽  
B. R. Miller ◽  
...  
Keyword(s):  
Growth Rate ◽  
Mole Fraction ◽  
Radiative Forcing ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Lower Troposphere ◽  
Emission Rates ◽  
Global Emission ◽  
Atmospheric Observations

Abstract. High-frequency, in situ observations from the Advanced Global Atmospheric Gases Experiment (AGAGE), for the period 2003 to 2012, combined with archive flask measurements dating back to 1977, have been used to capture the rapid growth of HFC-143a (CH3CF3) and HFC-32 (CH2F2) mole fractions and emissions into the atmosphere. Here we report the first in situ global measurements of these two gases. HFC-143a and HFC-32 are the third and sixth most abundant hydrofluorocarbons (HFCs) respectively and they currently make an appreciable contribution to the HFCs in terms of atmospheric radiative forcing (1.7 ± 0.04 and 0.7 ± 0.02 mW m−2 in 2012 respectively). In 2012 the global average mole fraction of HFC-143a was 13.4 ± 0.3 ppt (1σ) in the lower troposphere and its growth rate was 1.4 ± 0.04 ppt yr−1; HFC-32 had a global mean mole fraction of 6.2 ± 0.2 ppt and a growth rate of 1.1 ± 0.04 ppt yr−1 in 2012. The extensive observations presented in this work have been combined with an atmospheric transport model to simulate global atmospheric abundances and derive global emission estimates. It is estimated that 23 ± 3 Gg yr−1 of HFC-143a and 21 ± 11 Gg yr−1 of HFC-32 were emitted globally in 2012, and the emission rates are estimated to be increasing by 7 ± 5% yr−1 for HFC-143a and 14 ± 11% yr−1 for HFC-32.

scholarly journals MAMAP – a new spectrometer system for column-averaged methane and carbon dioxide observations from aircraft: retrieval algorithm and first inversions for point source emission rates

2011 ◽  
Vol 4 (9) ◽  
pp. 1735-1758 ◽  
Author(s):  
T. Krings ◽  
K. Gerilowski ◽  
M. Buchwitz ◽  
M. Reuter ◽  
A. Tretner ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Point Source ◽  
Integral Method ◽  
Power Plants ◽  
Retrieval Algorithm ◽  
Detailed Knowledge ◽  
Emission Rates ◽  
Gaussian Plume ◽  
Gaussian Integral ◽  
Source Emission

Abstract. MAMAP is an airborne passive remote sensing instrument designed to measure the dry columns of methane (CH4) and carbon dioxide (CO2). The MAMAP instrument comprises two optical grating spectrometers: the first observing in the short wave infrared band (SWIR) at 1590–1690 nm to measure CO2 and CH4 absorptions, and the second in the near infrared (NIR) at 757–768 nm to measure O2 absorptions for reference/normalisation purposes. MAMAP can be operated in both nadir and zenith geometry during the flight. Mounted on an aeroplane, MAMAP surveys areas on regional to local scales with a ground pixel resolution of approximately 29 m × 33 m for a typical aircraft altitude of 1250 m and a velocity of 200 km h−1. The retrieval precision of the measured column relative to background is typically &amp;lesssim;1% (1σ). MAMAP measurements are valuable to close the gap between satellite data, having global coverage but with a rather coarse resolution, on the one hand, and highly accurate in situ measurements with sparse coverage on the other hand. In July 2007, test flights were performed over two coal-fired power plants operated by Vattenfall Europe Generation AG: Jänschwalde (27.4 Mt CO2 yr−1) and Schwarze Pumpe (11.9 Mt CO2 yr−1), about 100 km southeast of Berlin, Germany. By using two different inversion approaches, one based on an optimal estimation scheme to fit Gaussian plume models from multiple sources to the data, and another using a simple Gaussian integral method, the emission rates can be determined and compared with emissions reported by Vattenfall Europe. An extensive error analysis for the retrieval's dry column results (XCO2 and XCH4) and for the two inversion methods has been performed. Both methods – the Gaussian plume model fit and the Gaussian integral method – are capable of deriving estimates for strong point source emission rates that are within ±10% of the reported values, given appropriate flight patterns and detailed knowledge of wind conditions.

scholarly journals Global emissions of HFC-143a (CH<sub>3</sub>CF<sub>3</sub>) and HFC-32 (CH<sub>2</sub>F<sub>2</sub>) from in situ and air archive atmospheric observations

2014 ◽  
Vol 14 (5) ◽  
pp. 6471-6500 ◽  
Author(s):  
S. O'Doherty ◽  
M. Rigby ◽  
J. Mühle ◽  
D. J. Ivy ◽  
B. R. Miller ◽  
...  
Keyword(s):  
Growth Rate ◽  
Mole Fraction ◽  
Radiative Forcing ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Lower Troposphere ◽  
Emission Rates ◽  
Global Emission ◽  
Atmospheric Observations

Abstract. High frequency, in situ observations from the Advanced Global Atmospheric Gases Experiment (AGAGE), for the period 2003 to 2012, combined with archive flask measurements dating back to 1977, have been used to capture the rapid growth of HFC-143a (CH3CF3) and HFC-32 (CH2F2) mole fractions and emissions into the atmosphere. Here we report the first in situ global measurements of these two gases. HFC-143a and HFC-32 are the third and sixth most abundant HFCs respectively and they currently make an appreciable contribution to the HFCs in terms of atmospheric radiative forcing (1.7 and 0.7 mW m2 in 2012, respectively). In 2012 the global average mole fraction of HFC-143a was 13.4 ± 0.3 ppt (1-sigma) in the lower troposphere and its growth rate was 1.4 ± 0.04 ppt yr−1; HFC-32 had a global mean mole fraction of 6.2 ± 0.2 ppt and a growth rate of 1.1 ± 0.04 ppt yr−1 in 2012. The extensive observations presented in this work have been combined with an atmospheric transport model to simulate global atmospheric abundances and derive global emission estimates. It is estimated that 23 ± 3 Gg yr−1 of HFC-143a and 21 ± 11 Gg yr−1 of HFC-32 were emitted globally in 2012, and the emission rates are estimated to be increasing 7 ± 5% yr−1 for HFC-143a and 14 ± 11% yr−1 for HFC-32.

scholarly journals Global emission estimates and radiative impact of C<sub>4</sub>F<sub>10</sub>, C<sub>5</sub>F<sub>12</sub>, C<sub>6</sub>F<sub>14</sub>, C<sub>7</sub>F<sub>16</sub> and C<sub>8</sub>F<sub>18</sub>

2012 ◽  
Vol 12 (5) ◽  
pp. 12987-13014 ◽  
Author(s):  
D. J. Ivy ◽  
M. Rigby ◽  
M. Baasandorj ◽  
J. B. Burkholder ◽  
R. G. Prinn
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Transport Model ◽  
Emission Rates ◽  
Chemical Transport Model ◽  
Bottom Up ◽  
Radiative Efficiency ◽  
Atmospheric Species ◽  
Global Emission ◽  
Atmospheric Observations

Abstract. Global emission estimates based on new atmospheric observations are presented for the acylic high molecular weight perfluorocarbons (PFCs): decafluorobutane (C4F10), dodecafluoropentane (C5F12), tetradecafluorohexane (C6F14), hexadecafluoroheptane (C7F16) and octadecafluorooctane (C8F18). Emissions are estimated using a 3-dimensional chemical transport model and an inverse method that includes a growth constraint on emissions. The observations used in the inversion are based on newly measured archived air samples that cover a 39-yr period, from 1973 to 2011, and include 36 Northern Hemispheric and 46 Southern Hemispheric samples (Ivy et al., 2012). The derived emission estimates show that global emission rates were largest in the 1980s and 1990s for C4F10 and C5F12, and in the 1990s for C6F14,C7F16 and C8F18. After a subsequent decline, emissions have remained relatively stable, within 20%, for the last 5 yr. Bottom-up emission estimates are available from the Emission Database for Global Atmospheric Research version 4.2 (EDGARv4.2) for C4F10, C5F12, C6F14 and C7F16, and inventories of C4F10, C5F12 andC6F14 are reported to the United Nations' Framework Convention on Climate Change (UNFCCC) by Annex 1 countries that have ratified the Kyoto Protocol. The atmospheric measurement based emission estimates are 20 times larger than EDGARv4.2 for C4F10 and over three orders of magnitude for C5F12. The derived emission estimates for C6F14 largely agree with the bottom-up estimates from EDGARv4.2. Moreover, the C7F16 emission estimates are comparable to those of EDGARv4.2 at their peak in the 1990s, albeit significant underestimation for the other time periods. There are no bottom-up emission estimates for C8F18, thus the emission rates reported here are the first for C8F18. The reported inventories for C4F10, C5F12 and C6F14 to UNFCCC are five to ten times lower than those estimated in this study. In addition, we present measured infrared absorption spectra for C7F16 and C8F18, and estimate their radiative efficiencies and global warming potentials (GWPs). We find that C8F18's radiative efficiency is similar to trifluoromethyl sulfur pentafluoride's (SF5CF3) at 0.57 W m−2 ppb−1, which is the highest radiative efficiency of any measured atmospheric species. Using the 100-yr time horizon GWPs, the high molecular weight perfluorocarbons studied here contributed up to 15.4% of the total PFC emissions in CO2 equivalents in 1997 and 6% of the total PFC emissions in 2009.

scholarly journals Detecting long-term changes in point source fossil CO<sub>2</sub> emissions with tree ring archives

2016 ◽  
Author(s):  
E. D. Keller ◽  
J. C. Turnbull ◽  
M. W. Norris
Keyword(s):  
Point Source ◽  
Co2 Emissions ◽  
Tree Ring ◽  
Power Plants ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Model Simulation ◽  
Point Sources ◽  
Long Term Changes

Abstract. We examine the utility of tree ring 14C archives for detecting long term changes in fossil CO2 emissions from a point source. Trees assimilate carbon from the atmosphere during photosynthesis, in the process faithfully recording the average atmospheric 14C content in each new annual tree ring. Using 14C as a proxy for fossil CO2, we examine interannual variability over six years of fossil CO2 observations between 2004-05 and 2011-12 from two trees growing near the Kapuni Natural Gas Plant in rural Taranaki, New Zealand. We quantify the amount of variability that can be attributed to transport and meteorology by simulating constant point source fossil CO2 emissions over the observation period with the atmospheric transport model WindTrax. We compare model simulation results to observations and calculate the amount of change in emissions that we can detect with new observations over annual or multi-year time periods given both measurement uncertainty of 1ppm and the modelled variation in transport. In particular, we ask, what is the minimum amount of change in emissions that we can detect using this method, given a reference period of six years? We find that changes of 42% or more could be detected in a new sample from one year at the same observation location, or 22% in the case of four years of new samples. This threshold lowers and the method becomes more practical the more the size of the signal increases. For point sources 10 times larger than the Kapuni plant (a more typical size for power plants worldwide), it would be possible to detect sustaine d emissions changes on the order of 10% given suitable meteorology and observations.

scholarly journals Optimizing a dynamic fossil fuel CO<sub>2</sub> emission model with CTDAS (v1.0) for an urban area using atmospheric observations of CO<sub>2</sub>, CO, NO<sub><i>x</i></sub>, and SO<sub>2</sub>

2019 ◽  
Author(s):  
Ingrid Super ◽  
Hugo A. C. Denier van der Gon ◽  
Michiel K. van der Molen ◽  
Stijn N. C. Dellaert ◽  
Wouter Peters
Keyword(s):  
Fossil Fuel ◽  
Covariance Structure ◽  
Traffic Density ◽  
Emission Model ◽  
Emission Rates ◽  
Activity Data ◽  
Modelling Framework ◽  
Novel Approach ◽  
Atmospheric Observations ◽  
Mean Differences

Abstract. We present a modelling framework for fossil fuel CO2 emissions in an urban environment, which allows constraints from emission inventories to be combined with atmospheric observations of CO2 and its co-emitted species CO, NOx, and SO2. Rather than a static assignment of average emission rates to each unit-area of the urban domain, the fossil fuel emissions we use are dynamic: they vary in time and space in relation to data that describe or approximate the activity within a sector, such as traffic density, power demand, 2 m temperature (as proxy for heating demand), and sunlight and wind speed (as proxies for renewable energy supply). Through inverse modelling, we optimize the relationships between these activity data and the resulting emissions of all species within the dynamic fossil fuel emission model, based on atmospheric mole fraction observations. The advantage of this novel approach is that the optimized parameters (emission factors and emission ratios, N = 44) in this dynamic model (a) vary much less over space and time, (b) allow a physical interpretation of mean and uncertainty, and (c) have better defined uncertainties and covariance structure. This makes them more suited to extrapolate, optimize, and interpret than the gridded emissions themselves. The merits of this approach are investigated using a pseudo-observation-based ensemble Kalman filter inversion setup for the Dutch Rijnmond area at 1 × 1 km resolution. We find that the dynamic fossil fuel model approximates the gridded emissions well (annual mean differences

scholarly journals Optimizing a dynamic fossil fuel CO<sub>2</sub> emission model with CTDAS (CarbonTracker Data Assimilation Shell, v1.0) for an urban area using atmospheric observations of CO<sub>2</sub>, CO, NO<sub><i>x</i></sub>, and SO<sub>2</sub>

2020 ◽  
Vol 13 (6) ◽  
pp. 2695-2721
Author(s):  
Ingrid Super ◽  
Hugo A. C. Denier van der Gon ◽  
Michiel K. van der Molen ◽  
Stijn N. C. Dellaert ◽  
Wouter Peters
Keyword(s):  
Co2 Emissions ◽  
Fossil Fuel ◽  
Covariance Structure ◽  
Traffic Density ◽  
Emission Model ◽  
Emission Rates ◽  
Activity Data ◽  
Atmospheric Observations ◽  
Fossil Fuel Emission ◽  
Emission Ratios

Abstract. We present a modelling framework for fossil fuel CO2 emissions in an urban environment, which allows constraints from emission inventories to be combined with atmospheric observations of CO2 and its co-emitted species CO, NOx, and SO2. Rather than a static assignment of average emission rates to each unit area of the urban domain, the fossil fuel emissions we use are dynamic: they vary in time and space in relation to data that describe or approximate the activity within a sector, such as traffic density, power demand, 2 m temperature (as proxy for heating demand), and sunlight and wind speed (as proxies for renewable energy supply). Through inverse modelling, we optimize the relationships between these activity data and the resulting emissions of all species within the dynamic fossil fuel emission model, based on atmospheric mole fraction observations. The advantage of this novel approach is that the optimized parameters (emission factors and emission ratios, N=44) in this dynamic emission model (a) vary much less over space and time, (b) allow for a physical interpretation of mean and uncertainty, and (c) have better defined uncertainties and covariance structure. This makes them more suited to extrapolate, optimize, and interpret than the gridded emissions themselves. The merits of this approach are investigated using a pseudo-observation-based ensemble Kalman filter inversion set-up for the Dutch Rijnmond area at 1 km×1 km resolution. We find that the fossil fuel emission model approximates the gridded emissions well (annual mean differences <2 %, hourly temporal r2=0.21–0.95), while reported errors in the underlying parameters allow a full covariance structure to be created readily. Propagating this error structure into atmospheric mole fractions shows a strong dominance of a few large sectors and a few dominant uncertainties, most notably the emission ratios of the various gases considered. If the prior emission ratios are either sufficiently well-known or well constrained from a dense observation network, we find that including observations of co-emitted species improves our ability to estimate emissions per sector relative to using CO2 mole fractions only. Nevertheless, the total CO2 emissions can be well constrained with CO2 as the only tracer in the inversion. Because some sectors are sampled only sparsely over a day, we find that propagating solutions from day-to-day leads to largest uncertainty reduction and smallest CO2 residuals over the 14 consecutive days considered. Although we can technically estimate the temporal distribution of some emission categories like shipping separate from their total magnitude, the controlling parameters are difficult to distinguish. Overall, we conclude that our new system looks promising for application in verification studies, provided that reliable urban atmospheric transport fields and reasonable a priori emission ratios for CO2 and its co-emitted species can be produced.

scholarly journals Estimation of the fossil-fuel component in atmospheric CO<sub>2</sub> based on radiocarbon measurements at the Beromünster tall tower, Switzerland

2017 ◽  
Author(s):  
Tesfaye A. Berhanu ◽  
Sonke Szidat ◽  
Dominik Brunner ◽  
Ece Satar ◽  
Rudiger Schanda ◽  
...  
Keyword(s):  
Power Plants ◽  
Large Scale ◽  
Fossil Fuel ◽  
Transport Model ◽  
Vertical Mixing ◽  
Fuel Component ◽  
Mixing Ratios ◽  
Tall Tower ◽  
Emission Ratios

Abstract. Fossil fuel CO2 (CO2ff) is the major contributor of anthropogenic CO2 in the atmosphere, and accurate quantification is essential to better understand the carbon cycle. Since October 2012, we have been continuously measuring the mixing ratios of CO, CO2, CH4 and H2O at five different heights at the Beromünster tall tower, Switzerland. Air samples for radiocarbon (Δ14CO2) analysis have also been collected from the 212.5 m sampling inlet of the tower on a bi-weekly basis. A correction was applied for 14CO2 emissions from nearby nuclear power plants (NPPs), which have been simulated with the Lagrangian transport model FLEXPART-COSMO. The 14CO2 emissions from NPPs offset the depletion in 14C by fossil-fuel emissions resulting in an underestimation of the fossil-fuel component in atmospheric CO2 by about 16 %. An average observed ratio (RCO) of 13.4 ± 1.3 mmol/mol was calculated from the enhancements in CO mixing ratios relative to the clean air reference site Jungfraujoch (ΔCO) and the radiocarbon-based fossil-fuel CO2 mole fractions. This ratio is significantly higher than both the mean anthropogenic CO/CO2 emission ratios estimated for Switzerland from the national inventory (7.8 mmol/mol for 2013), and the ratio between in-situ measured CO and CO2 enhancements at Beromünster over the Jungfraujoch background (8.3 mmol/mol). Differences could not yet be assigned to specific processes and shortcomings of these two methods but may originate from locally variable emission ratios as well as from non-fossil emissions and biospheric contributions. By combining the ratio derived using the radiocarbon measurements and the in-situ measured CO mixing ratios, a high-resolution time series of CO2ff was calculated exhibiting a clear seasonality driven by seasonal variability in emissions and vertical mixing. By subtracting the fossil-fuel component and the large-scale background, we have determined the regional biospheric CO2 component that is characterized by seasonal variations ranging between −15 to +30 ppm. A pronounced diurnal variation was observed during summer modulated by biospheric exchange and vertical mixing while no consistent pattern was found during winter.

scholarly journals Atmospheric measurement of point source fossil fuel CO<sub>2</sub> emissions

2013 ◽  
Vol 13 (11) ◽  
pp. 29059-29095
Author(s):  
J. C. Turnbull ◽  
E. D. Keller ◽  
W. T. Baisden ◽  
G. Brailsford ◽  
T. Bromley ◽  
...  
Keyword(s):  
Point Source ◽  
Fossil Fuel ◽  
Dispersion Model ◽  
Treatment Plant ◽  
Plume Dispersion ◽  
Atmospheric Measurements ◽  
Gas Treatment ◽  
Atmospheric Observations ◽  
Meteorological Observations

Abstract. We use the Kapuni Gas Treatment Plant to examine methodologies for atmospheric monitoring of point source fossil fuel CO2 (CO2ff) emissions. The Kapuni plant, located in rural New Zealand, removes CO2 from locally extracted natural gas and vents that CO2 to the atmosphere, at a rate of ~0.1 Tg carbon per year. The plant is located in a rural dairy farming area, with no other significant CO2ff sources nearby, but large, diurnally varying, biospheric CO2 fluxes from the surrounding highly productive agricultural grassland. We made flask measurements of CO2 and 14CO2 (from which we derive the CO2ff component) and in situ measurements of CO2 downwind of the Kapuni plant, using a Helikite to sample transects across the emission plume from the surface up to 100 m a.g.l. We also determined the surface CO2ff content averaged over several weeks from the 14CO2 content of grass samples collected from the surrounding area. We use the WindTrax plume dispersion model to compare the atmospheric observations with the emissions reported by the Kapuni plant, and to determine how well atmospheric measurements can constrain the emissions. The model has difficulty accurately capturing the fluctuations and short-term variability in the Helikite samples, but does quite well in representing the observed CO2ff in 15 min averaged surface flask samples and in ~1 week integrated CO2ff averages from grass samples. In this pilot study, we found that using grass samples, the modeled and observed CO2ff emissions averaged over one week agreed to within 30%. The results imply that greater verification accuracy may be achieved by including more detailed meteorological observations and refining 14CO2 sampling strategies.

scholarly journals Estimation of the fossil fuel component in atmospheric CO<sub>2</sub> based on radiocarbon measurements at the Beromünster tall tower, Switzerland

2017 ◽  
Vol 17 (17) ◽  
pp. 10753-10766 ◽  
Author(s):  
Tesfaye A. Berhanu ◽  
Sönke Szidat ◽  
Dominik Brunner ◽  
Ece Satar ◽  
Rüdiger Schanda ◽  
...  
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Large Scale ◽  
Fossil Fuel ◽  
Transport Model ◽  
Vertical Mixing ◽  
Fuel Component ◽  
Mixing Ratios ◽  
Tall Tower

Abstract. Fossil fuel CO2 (CO2ff) is the major contributor of anthropogenic CO2 in the atmosphere, and accurate quantification is essential to better understand the carbon cycle. Since October 2012, we have been continuously measuring the mixing ratios of CO, CO2, CH4, and H2O at five different heights at the Beromünster tall tower, Switzerland. Air samples for radiocarbon (Δ14CO2) analysis have also been collected from the highest sampling inlet (212.5 m) of the tower on a biweekly basis. A correction was applied for 14CO2 emissions from nearby nuclear power plants (NPPs), which have been simulated with the Lagrangian transport model FLEXPART-COSMO. The 14CO2 emissions from NPPs offset the depletion in 14C by fossil fuel emissions, resulting in an underestimation of the fossil fuel component in atmospheric CO2 by about 16 %. An average observed ratio (RCO) of 13.4 ± 1.3 mmol mol−1 was calculated from the enhancements in CO mixing ratios relative to the clean-air reference site Jungfraujoch (ΔCO) and the radiocarbon-based fossil fuel CO2 mole fractions. The wintertime RCO estimate of 12.5 ± 3.3 is about 30 % higher than the wintertime ratio between in situ measured CO and CO2 enhancements at Beromünster over the Jungfraujoch background (8.7 mmol mol−1) corrected for non-fossil contributions due to strong biospheric contribution despite the strong correlation between ΔCO and ΔCO2 in winter. By combining the ratio derived using the radiocarbon measurements and the in situ measured CO mixing ratios, a high-resolution time series of CO2ff was calculated exhibiting a clear seasonality driven by seasonal variability in emissions and vertical mixing. By subtracting the fossil fuel component and the large-scale background, we have determined the regional biospheric CO2 component that is characterized by seasonal variations ranging between −15 and +30 ppm. A pronounced diurnal variation was observed during summer modulated by biospheric exchange and vertical mixing, while no consistent pattern was found during winter.

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