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Since 2004, atmospheric carbon dioxide (CO2) is being measured at the High Altitude Research Station Jungfraujoch by the division of Climate and Environmental Physics at the University of Bern (KUP) using a nondispersive infrared gas analyzer (NDIR) in combination with a paramagnetic O2 analyzer. In January 2010, CO2 measurements based on cavity ring-down spectroscopy (CRDS) as part of the Swiss National Air Pollution Monitoring Network were added by the Swiss Federal Laboratories for Materials Science and Technology (Empa). To ensure a smooth transition – a prerequisite when merging two data sets, e.g., for trend determinations – the two measurement systems run in parallel for several years. Such a long-term intercomparison also allows the identification of potential offsets between the two data sets and the collection of information about the compatibility of the two systems on different time scales. A good agreement of the seasonality, short-term variations and, to a lesser extent mainly due to the short common period, trend calculations is observed. However, the comparison reveals some issues related to the stability of the calibration gases of the KUP system and their assigned CO2 mole fraction. It is possible to adapt an improved calibration strategy based on standard gas determinations, which leads to better agreement between the two data sets. By excluding periods with technical problems and bad calibration gas cylinders, the average hourly difference (CRDS – NDIR) of the two systems is −0.03 ppm ± 0.25 ppm. Although the difference of the two data sets is in line with the compatibility goal of ±0.1 ppm of the World Meteorological Organization (WMO), the standard deviation is still too high. A significant part of this uncertainty originates from the necessity to switch the KUP system frequently (every 12 min) for 6 min from ambient air to a working gas in order to correct short-term variations of the O2 measurement system. Allowing additional time for signal stabilization after switching the sample, an effective data coverage of only one-sixth for the KUP system is achieved while the Empa system has a nearly complete data coverage. Additionally, different internal volumes and flow rates may affect observed differences.

Radiocarbon dioxide (14CO2, reported in Δ14CO2) can be used to determine the fossil fuel CO2 addition to the atmosphere, since fossil fuel CO2 no longer contains any 14C. After the release of CO2 at the source, atmospheric transport causes dilution of strong local signals into the background and detectable gradients of Δ14CO2 only remain in areas with high fossil fuel emissions. This fossil fuel signal can moreover be partially masked by the enriching effect that anthropogenic emissions of 14CO2 from the nuclear industry have on the atmospheric Δ14CO2 signature. In this paper, we investigate the regional gradients in 14CO2 over the European continent and quantify the effect of the emissions from nuclear industry. We simulate the emissions and transport of fossil fuel CO2 and nuclear 14CO2 for Western Europe using the Weather Research and Forecast model (WRF-Chem) for a period covering 6 summer months in 2008. We evaluate the expected CO2 gradients and the resulting Δ14CO2 in simulated integrated air samples over this period, as well as in simulated plant samples. We find that the average gradients of fossil fuel CO2 in the lower 1200 m of the atmosphere are close to 15 ppm at a 12 km × 12 km horizontal resolution. The nuclear influence on Δ14CO2 signatures varies considerably over the domain and for large areas in France and the UK it can range from 20 to more than 500% of the influence of fossil fuel emissions. Our simulations suggest that the resulting gradients in Δ14CO2 are well captured in plant samples, but due to their time-varying uptake of CO2, their signature can be different with over 3‰ from the atmospheric samples in some regions. We conclude that the framework presented will be well-suited for the interpretation of actual air and plant 14CO2 samples.

The 222Radon tracer method is a powerful tool to estimate local and regional surface emissions of, e.g., greenhouse gases. In this paper we demonstrate that in practice, the method as it is commonly used, produces inaccurate results in case of nonhomogeneously spread emission sources, and we propose a different approach to account for this. We have applied the new methodology to ambient observations of CO2 and 222Radon to estimate CO2 surface emissions for the city of Bern, Switzerland. Furthermore, by utilizing combined measurements of CO2 and δ(O2/N2) we obtain valuable information about the spatial and temporal variability of the main emission sources. Mean net CO2 emissions based on 2 years of observations are estimated at (11.2 ± 2.9) kt km−2 a−1. Oxidative ratios indicate a significant influence from the regional biosphere in summer/spring and fossil fuel combustion processes in winter/autumn. Our data indicate that the emissions from fossil fuels are, to a large degree, related to the combustion of natural gas which is used for heating purposes.

We present results from an intercomparison program of CO2, δ(O2/N2) and δ13CO2 measurements from atmospheric flask samples. Flask samples are collected on a bi-weekly basis at the High Altitude Research Station Jungfraujoch in Switzerland for three European laboratories: the University of Bern, Switzerland, the University of Groningen, the Netherlands and the Max Planck Institute for Biogeochemistry in Jena, Germany. Almost 4 years of measurements of CO2, δ(O2/N2) and δ13CO2 are compared in this paper to assess the measurement compatibility of the three laboratories. While the average difference for the CO2 measurements between the laboratories in Bern and Jena meets the required compatibility goal as defined by the World Meteorological Organization, the standard deviation of the average differences between all laboratories is not within the required goal. However, the obtained annual trend and seasonalities are the same within their estimated uncertainties. For δ(O2/N2) significant differences are observed between the three laboratories. The comparison for δ13CO2 yields the least compatible results and the required goals are not met between the three laboratories. Our study shows the importance of regular intercomparison exercises to identify potential biases between laboratories and the need to improve the quality of atmospheric measurements.

We report results from our atmospheric flask sampling network for three European sites: Lutjewad in the Netherlands, Mace Head in Ireland and the North Sea F3 platform. The air samples from these stations are analyzed for their CO2 and O2 concentrations. In this paper we present the CO2 and O2 data series from these sites between 1998 and 2009, as well as the atmospheric potential oxygen (APO). The seasonal pattern and long term trends agree to a large extent between our three measurement locations. We however find a changing gradient between Mace Head and Lutjewad, both for CO2 and O2. To explain the potential contribution of fossil fuel emissions to this changing gradient we use an atmospheric transport model in combination with CO2 emission data and information on the fossil fuel mix per region. Using the APO trend from Mace Head we obtain an estimate for the global oceanic CO2 uptake of 1.8 ± 0.8 PgC/year.

We present net emission estimates of CH4 and N2O of The Netherlands based on measurements conducted during the period of May 2006 to April 2009 at station Lutjewad, The Netherlands (6°21' E, 53°24' N, 1 m a.s.l.). 222Radon mixing ratios were applied as an indicator for vertical mixing and long-range air mass transport and used to calculate the net surface fluxes from atmospheric mixing ratios of CH4 and N2O. Our study shows that our measurement site Lutjewad is well-suited to measure emissions from The Netherlands and validation of the national inventories using the 222Radon flux method. Since this study is purely observation-based it is independent from inventories or atmospheric models. Our results are compared to the national inventories as reported to the UNFCCC. We found net emissions of: (15.2±5.3) t km−2 a−1 for CH4 and (0.9±0.3) t km−2 a−1 for N2O. These values are lower than the inventory-based emissions (2006-2008 averages) of (18.3±3.3) t km−2 a−1 for CH4, and (1.3±0.6) t km−2 a−1 for N2O, but the differences are insignificant.

We present an adapted gas chromatograph capable of measuring simultaneously and semi-continuously the atmospheric mixing ratios of the greenhouse gases CO2, CH4, N2O and SF6 and the trace gas CO with high precision and long-term stability. The novelty of our design is that all species are measured with only one device, making it a very cost-efficient system. No time lags are introduced between the measured mixing ratios. The system is designed to operate fully autonomously which makes it ideal for measurements at remote and unmanned stations. Only a small amount of sample air is needed, which makes this system also highly suitable for flask air measurements. In principle, only two reference cylinders are needed for daily operation and only one calibration per year against international WMO standards is sufficient to obtain high measurement precision and accuracy. The system described in this paper is in use since May 2006 at our atmospheric measurement site Lutjewad near Groningen, The Netherlands at 6°21' E, 53°24' N, 1 m a.s.l. Results show the long-term stability of the system. Observed measurement precisions at our remote research station Lutjewad were: ±0.04 ppm for CO2, ±0.8 ppb for CH4, ±0.8 ppb for CO, ±0.3 ppb for N2O, and ±0.1 ppt for SF6. The ambient mixing ratios of all measured species as observed at station Lutjewad for the period of May 2007 to August 2008 are presented as well.

We present atmospheric CO2 and delta(O-2/N-2) from flask samples taken on board aircraft over Fyodorovskoye (56 degrees 27'N, 32 degrees 55'E) at heights of 3000 m and 100 m between 1998 and 2008. The long-term trends for CO2 and delta(O-2/N-2) are similar for both sampling heights, and also similar to observations from marine background station Mace Head (Ireland) and coastal station Lutjewad (the Netherlands). The seasonal CO2 amplitude at 100 m was almost twice as large as at 3000 m and a phase shift in the seasonality of about two weeks between both sampling heights was observed. This indicates a dominant influence on CO2 in the boundary layer from the regional biosphere which is confirmed by analysis of the delta(O-2/N-2) to CO2 oxidative ratio (OR). Together with simulations with the TM3 model, our data suggest that the observed OR of -1.7 +/- 0.2 in the free troposphere is mainly driven by exchange processes with the ocean. Within the boundary layer an OR of -0.89 +/- 0.12 was observed which supports the results of other recent studies suggesting the commonly used value of -1.1 for biospheric OR is likely too low. (C) 2014 Elsevier Ltd. All rights reserved.

CO2 fluxes for the Netherlands and surroundings are estimated for the year 2008, from concentration measurements at four towers, using an inverse model. The results are compared to direct CO2 flux measurements by aircraft, for 6 flight tracks over the Netherlands, flown multiple times in each season. We applied the Regional Atmospheric Mesoscale Modeling system (RAMS) coupled to a simple carbon flux scheme (including fossil fuel), which was run at 10 km resolution, and inverted with an Ensemble Kalman Filter. The domain had 6 eco-regions, and inversions were performed for the four seasons separately. Inversion methods with pixel-dependent and -independent parameters for each eco-region were compared. The two inversion methods, in general, yield comparable flux averages for each eco-region and season, whereas the difference from the prior flux may be large. Posterior fluxes co-sampled along the aircraft flight tracks are usually much closer to the observations than the priors, with a comparable performance for both inversion methods, and with best performance for summer and autumn. The inversions showed more negative CO2 fluxes than the priors, though the latter are obtained from a biosphere model optimized using the Fluxnet database, containing observations from more than 200 locations worldwide. The two different crop ecotypes showed very different CO2 uptakes, which was unknown from the priors. The annual-average uptake is practically zero for the grassland class and for one of the cropland classes, whereas the other cropland class had a large net uptake, possibly because of the abundance of maize there.

Surface emissions of CO2 from fossil fuel combustion (ϕFFCO2) are estimated for the Netherlands for the period of May 2006–June 2009 using ambient atmospheric observations taken at station Lutjewad in the Netherlands (6°21′E, 53°24′N, 1 m. a.s.l.). Measurements of Δ14C on 2-weekly integrations of CO2 and CO mixing ratios are combined to construct a quasi-continuous proxy record (FFCO2*) from which surface fluxes (ϕFFCO2*) are determined using the 222Rn flux method. The trajectories of the air masses are analysed to determine emissions, which are representative for the Netherlands. We compared our observationally based estimates to the national inventories and we evaluated our methodology using the regional atmospheric transport model REMO. Based on 3 yr of observations we find annual mean ϕFFCO2* emissions of (4.7 ± 1.6) kt km-2 a-1 which is in very good agreement with the Dutch inventories of (4.5 ± 0.2) kt km-2 a-1 (average of 2006–2008).DOI: 10.1111/j.1600-0889.2010.00493.x

A new atmospheric measurement station has been established on the North Sea oil and gas production platform F3, 200 km north off the Dutch coast (5°51' N, 4°44' E). Atmospheric concentrations of O2 and CO2 are continuously measured using fuel cell technology and compact infrared absorption instruments, respectively. Furthermore, the station includes an automated air flask sampler for laboratory analysis of the atmospheric concentrations of CO2, CH4, CO and O2 and isotope measurements of δ13C, δ18O and Δ14C from CO2. This station is the first fixed sea based station with on-site continuous O2 and CO2 measurements and therefore yields valuable information about the CO2 uptake in coastal marine regions, specifically the North Sea. This paper presents the measurement station and the used methodologies in detail. In comparison to land-based stations, the data show low day-to-day variability, as they are practically free of nightly inversions as well as human influences, due to the station's remoteness. Therefore, the data set collected at this measurement station serves directly as background data for the coastal northwest European region. Additionally, the first data are presented showing the seasonal cycle as expected during August 2008 through June 2009. Furthermore, some short-term O2 and CO2 signals are presented. The observations at the platform include several large and fast changing negative atmospheric O2 excursions without an accompanying change in the CO2 signal, which most likely indicate marine O2 uptake.

Surface emissions of CO2 from fossil fuel combustion (phi FFCO2) are estimated for the Netherlands for the period of May 2006-June 2009 using ambient atmospheric observations taken at station Lutjewad in the Netherlands (6 degrees 21'E, 53 degrees 24'N, 1 m. a.s.l.). Measurements of delta 14C on 2-weekly integrations of CO2 and CO mixing ratios are combined to construct a quasi-continuous proxy record (FFCO2*) from which surface fluxes (phi FFCO2*) are determined using the 222Rn flux method. The trajectories of the air masses are analysed to determine emissions, which are representative for the Netherlands. We compared our observationally based estimates to the national inventories and we evaluated our methodology using the regional atmospheric transport model REMO. Based on 3 yr of observations we find annual mean phi FFCO2* emissions of (4.7 +/- 1.6) kt km-2 a-1 which is in very good agreement with the Dutch inventories of (4.5 +/- 0.2) kt km-2 a-1 (average of 2006-2008).