Air–Sea Fluxes of Greenhouse Gases and Oxygen in the Northern Benguela Current Region During Upwelling Events

Abstract. Ground-based atmospheric observations of CO2, δ(O2/N2), N2O, and CH4 were used to make top-down estimates of the air–sea fluxes of these species from the Lüderitz and Walvis Bay upwelling cells in the northern Benguela region, during upwelling events. Average flux densities (±1σ) were 0.64 ± 0.4 μmol m−2 sec−1 for CO2, −5.1 ± 1.4 μmol m−2 sec−1 for O2 (as APO), 0.57 ± 0.3 nmol m−2 sec−1 for N2O, and 4.3 ± 5.5 nmol m−2 sec−1 for CH4. A comparison of our top-down flux estimates with shipboard-based measurements showed good agreement between both approaches. During the study, upwelling events were sources of CO2, N2O, and CH4 to the atmosphere. N2O fluxes were fairly low, in accordance with previous work suggesting that the evasion of this gas from the Benguela is smaller than for other Eastern Boundary Upwelling Systems (EBUS). Conversely, CH4 release was quite high for the marine environment, a result that supports studies that indicated a large sedimentary source of CH4 in the Walvis Bay area. These results demonstrate the suitability of atmospheric time series for characterizing the temporal variability of upwelling events and their influence on the overall marine GHG emissions from the northern Benguela region.

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Air–sea fluxes of greenhouse gases and oxygen in the northern Benguela Current region during upwelling events

Biogeosciences ◽

10.5194/bg-16-4065-2019 ◽

2019 ◽

Vol 16 (20) ◽

pp. 4065-4084 ◽

Cited By ~ 1

Author(s):

Eric J. Morgan ◽

Jost V. Lavric ◽

Damian L. Arévalo-Martínez ◽

Hermann W. Bange ◽

Tobias Steinhoff ◽

...

Keyword(s):

Flux Density ◽

Ghg Emissions ◽

Top Down ◽

Density Estimates ◽

Bay Area ◽

Benguela Current ◽

Atmospheric Observations ◽

Current Region ◽

Average Flux ◽

Sedimentary Source

Abstract. Ground-based atmospheric observations of CO2, δ(O2∕N2), N2O, and CH4 were used to make estimates of the air–sea fluxes of these species from the Lüderitz and Walvis Bay upwelling cells in the northern Benguela region, during upwelling events. Average flux densities (±1σ) were 0.65±0.4 µmol m−2 s−1 for CO2, -5.1±2.5 µmol m−2 s−1 for O2 (as APO), 0.61±0.5 nmol m−2 s−1 for N2O, and 4.8±6.3 nmol m−2 s−1 for CH4. A comparison of our top-down (i.e., inferred from atmospheric anomalies) flux estimates with shipboard-based measurements showed that the two approaches agreed within ±55 % on average, though the degree of agreement varied by species and was best for CO2. Since the top-down method overestimated the flux density relative to the shipboard-based approach for all species, we also present flux density estimates that have been tuned to best match the shipboard fluxes. During the study, upwelling events were sources of CO2, N2O, and CH4 to the atmosphere. N2O fluxes were fairly low, in accordance with previous work suggesting that the evasion of this gas from the Benguela is smaller than for other eastern boundary upwelling systems (EBUS). Conversely, CH4 release was quite high for the marine environment, a result that supports studies that indicated a large sedimentary source of CH4 in the Walvis Bay area. These results demonstrate the suitability of atmospheric time series for characterizing the temporal variability of upwelling events and their influence on the overall marine greenhouse gas (GHG) emissions from the northern Benguela region.

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Swiss halocarbon emissions for 2019 to 2020 assessed from regional atmospheric observations

10.5194/acp-2021-633 ◽

2021 ◽

Author(s):

Dominique Rust ◽

Ioannis Katharopoulos ◽

Martin K. Vollmer ◽

Stephan Henne ◽

Simon O'Doherty ◽

...

Keyword(s):

Atmospheric Transport ◽

Anthropogenic Activities ◽

Stratospheric Ozone ◽

Ratio Method ◽

Top Down ◽

Country Level ◽

Hfc 134A ◽

Atmospheric Observations ◽

Modelling Methods ◽

Good Agreement

Abstract. Halocarbons are emitted by various anthropogenic activities to the atmosphere, where they contribute to global warming and stratospheric ozone-depletion. To determine national halocarbon emissions, the so-called "top-down" approach relies on atmospheric observations, at sites that reflect emissions on a country level, and com-bines these observations with inverse modelling methods. In this study, we present 12 months (September 2019 to September 2020) of continuous atmospheric observations of 28 halocarbons from a measurement campaign at the Beromünster tall tower in Switzerland. The site is sensitive to the most densely populated area of Switzer-land, the Swiss Plateau, thus the measurements were well suited to derive Swiss halocarbon emissions. Emissions were calculated by two different top-down methods, a tracer-ratio method (TRM) with carbon monoxide (CO) as the independent tracer, and a Bayesian inversion (BI), based on atmospheric transport simulations using FLEXPART–COSMO. The results were compared to previously reported top-down emission estimates, based on measurements at the high-Alpine site Jungfraujoch, and to the "bottom-up" Swiss national greenhouse gas (GHG) inventory, as annually reported to the United Nations Framework Convention on Climate Change (UN-FCCC). We observed ongoing outgassing from existing foams and refrigerators for the ozone-depleting, banned chlorofluorocarbons (CFCs) and the regulated hydrochlorofluorocarbons (HCFCs), confirming their large historical use. For the major hydrofluorocarbons (HFCs) HFC-125 (CHF2CF3) and HFC-32 (CH2F2), our calcu-lated emissions of 99 ± 29 Mg yr−1 and 46 ± 13 Mg yr−1 were in good agreement with the national Swiss inventory values, whereas for HFC 134a (CH2FCF3) our result of 300 ± 85 Mg yr−1 was about 30 % lower than the UNFCCC reported value. For the other investigated HFCs, perfluorocarbons (PFCs), SF6 and NF3, emissions were small and in agreement with the inventory. Finally, we report the first country-based emission estimates of a total of 50 Mg yr−1 for three recently phased-in, unregulated hydrofluoroolefins (HFOs), HFO 1234yf (CF3CF=CH2), HFO-1234ze(E) ((E)-CF3CH=CHF) and HCFO-1233zd(E) ((E) CF3CH=CHCl).

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Analysis of Total Column CO2 and CH4 Measurements in Berlin with WRF-GHG

10.5194/acp-2018-1116 ◽

2019 ◽

Author(s):

Xinxu Zhao ◽

Julia Marshall ◽

Stephan Hachinger ◽

Christoph Gerbig ◽

Jia Chen

Keyword(s):

Urban Areas ◽

Initial Conditions ◽

Ghg Emissions ◽

Concentration Field ◽

Weather Research And Forecasting ◽

Background Concentration ◽

Wind Fields ◽

Simulated Wind ◽

Global Population ◽

Good Agreement

Abstract. Though they cover less than 3 % of the global land area, urban areas are responsible for over 70 % of the global greenhouse gas (GHG) emissions and contain 55 % of the global population. A quantitative tracking of GHG emissions in urban areas is therefore of great importance, with the aim of accurately assessing the amount of emissions and identifying the emission sources. The Weather Research and Forecasting model (WRF) coupled with GHG modules (WRF-GHG) developed for mesoscale atmospheric GHG transport, can predict column-averaged abundances of CO2 and CH4 (XCO2 and XCH4). In this study, we use WRF-GHG to model the Berlin area at a high spatial resolution of 1 km. The simulated wind and concentration fields were compared with the measurements from a campaign performed around Berlin in 2014 (Hase et al., 2015). The measured and simulated wind fields mostly demonstrate good agreement and the simulated XCO2 agrees well with the measurement. In contrast, a bias in the simulated XCH4 of around 2.7 % is found, caused by relatively high initialization values for the background concentration field. We find that an analysis using differential column methodology (DCM) works well for the XCH4 comparison, as corresponding background biases then cancel out. From the tracer analysis, we find that the enhancement of XCH4 is highly dependent on human activities. The XCO2 signal in the vicinity of Berlin is dominated by anthropogenic behavior rather than biogenic activities. We conclude that DCM is an effective method for comparing models to observations independently of biases caused, e.g., by initial conditions. It allows us to use our high resolution WRF-GHG model to detect and understand sources of GHG emissions quantitatively in urban areas.

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Using emissions derived from atmospheric observations to inform the reported UK inventory

10.5194/egusphere-egu21-7486 ◽

2021 ◽

Author(s):

Alistair Manning ◽

Alison Redington ◽

Simon O'Doherty ◽

Dickon Young ◽

Dan Say ◽

...

Keyword(s):

Best Practice ◽

Dispersion Model ◽

Regional Scale ◽

Atmospheric Dispersion ◽

Three Dimensional ◽

Ghg Emissions ◽

Atmospheric Observations ◽

Emission Modelling ◽

National Inventory Report ◽

The Uk

Verification of the nationally reported greenhouse gas (GHG) inventories using inverse modelling and atmospheric observations is considered to be best practice by the United Nations Framework Convention on Climate Change (UNFCCC). It allows for an independent assessment of the nationally reported GHG emissions using a comprehensively different approach to the inventory methods. Significant differences in the emissions estimated using the two approaches are a means of identifying areas worthy of further investigation.&#160;An inversion methodology called Inversion Technique for Emission Modelling (InTEM) has been developed that uses a non-negative least squares minimisation technique to determine the emission magnitude and distribution that most accurately reproduces the observations. By estimating the underlying baseline time series, atmospheric concentrations where the short-term impact of regional pollution has been removed, and by modelling where the air has passed over on route to the observation stations on a regional scale, estimates of UK emissions are made. In this study we use an extensive network of observations with six stations across the UK and six more in neighbouring countries. InTEM uses information from a Lagrangian dispersion model NAME (Numerical Atmospheric dispersion Modelling Environment), driven by three-dimensional, modelled meteorology, to understand how the air mixes during transport from the emission sources to observation points. The InTEM inversion results are submitted annually by the UK as part of their National Inventory Report to the UNFCCC. They are used within the UK inventory team to highlight areas for investigation and have led to significant improvements to the submitted UK inventory. The latest UK comparisons will be shown along with examples of how the inversion results have informed the inventory.

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Emissions of Carbon Tetrachloride (CCl4) from Europe

10.5194/acp-2016-326 ◽

2016 ◽

Author(s):

Francesco Graziosi ◽

Jgor Arduini ◽

Paolo Bonasoni ◽

Francesco Furlani ◽

Umberto Giostra ◽

...

Keyword(s):

Carbon Tetrachloride ◽

Large Scale ◽

Stratospheric Ozone ◽

Montreal Protocol ◽

Scale Production ◽

Top Down ◽

Significant Discrepancy ◽

Bottom Up ◽

Atmospheric Observations ◽

Global Emissions

Abstract. Carbon tetrachloride (CCl4) is a long-lived radiatively-active compound able to destroy stratospheric ozone. Due to its inclusion in the Montreal Protocol on Substances that Deplete the Ozone Layer, the last two decades have seen a sharp decrease in its large scale emissive use with a consequent decline of its atmospheric mole fractions. However, the Montreal Protocol restrictions do not apply to the use of carbon tetrachloride as feedstock for the production of other chemicals, implying the risk of fugitive emissions from the industry sector. The occurrence of such unintended emissions is suggested by a significant discrepancy between global emissions as derived by reported production and feedstock usage (bottom-up emissions), and those based on atmospheric observations (top-down emissions). In order to better constrain the atmospheric budget of carbon tetrachloride, several studies based on a combination of atmospheric observations and inverse modelling have been conducted in recent years in various regions of the world. This study is focused on the European scale and based on long-term high-frequency observations at three European sites, combined with a Bayesian inversion methodology. We estimated that average European emissions for 2006–2014 were 2.3 (± 0.8) Gg yr−1, with an average decreasing trend of 7.3 % per year. Our analysis identified France as the main source of emissions over the whole study period, with an average contribution to total European emissions of 25 %. The inversion was also able to allow the localisation of emission "hot-spots" in the domain, with major source areas in Southern France, Central England (UK) and Benelux (Belgium, The Netherlands, Luxembourg), where most of industrial scale production of basic organic chemicals are located. According to our results, European emissions correspond to 4.0 % of global emissions for 2006–2012. Together with other regional studies, our results allow a better constraint of the global budget of carbon tetrachloride and a better quantification of the gap between top-down and bottom-up estimates.

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Analysis of total column CO2 and CH4 measurements in Berlin with WRF-GHG

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-11279-2019 ◽

2019 ◽

Vol 19 (17) ◽

pp. 11279-11302 ◽

Cited By ~ 2

Author(s):

Xinxu Zhao ◽

Julia Marshall ◽

Stephan Hachinger ◽

Christoph Gerbig ◽

Matthias Frey ◽

...

Keyword(s):

Urban Areas ◽

Initial Conditions ◽

Ghg Emissions ◽

Weather Research And Forecasting ◽

Wind Fields ◽

High Background ◽

Simulated Wind ◽

Global Population ◽

Total Column ◽

Good Agreement

Abstract. Though they cover less than 3 % of the global land area, urban areas are responsible for over 70 % of the global greenhouse gas (GHG) emissions and contain 55 % of the global population. A quantitative tracking of GHG emissions in urban areas is therefore of great importance, with the aim of accurately assessing the amount of emissions and identifying the emission sources. The Weather Research and Forecasting model (WRF) coupled with GHG modules (WRF-GHG) developed for mesoscale atmospheric GHG transport can predict column-averaged abundances of CO2 and CH4 (XCO2 and XCH4). In this study, we use WRF-GHG to model the Berlin area at a high spatial resolution of 1 km. The simulated wind and concentration fields were compared with the measurements from a campaign performed around Berlin in 2014 (Hase et al., 2015). The measured and simulated wind fields mostly demonstrate good agreement. The simulated XCO2 shows quite similar trends with the measurement but with approximately 1 ppm bias, while a bias in the simulated XCH4 of around 2.7 % is found. The bias could potentially be the result of relatively high background concentrations, the errors at the tropopause height, etc. We find that an analysis using differential column methodology (DCM) works well for the XCH4 comparison, as corresponding background biases are then canceled out. From the tracer analysis, we find that the enhancement of XCH4 is highly dependent on human activities. The XCO2 enhancement in the vicinity of Berlin is dominated by anthropogenic behavior rather than biogenic activities. We conclude that DCM is an effective method for comparing models to observations independently of biases caused, e.g., by initial conditions. It allows us to use our high-resolution WRF-GHG model to detect and understand major sources of GHG emissions in urban areas.

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