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110 CHAPTER 2. ATMOSPHERE AND REMOTE SENSING 2.7.3 Coupling and modernisation of the Heidelberg Greenhouse Gases and CO - GC systems for continuous measurements Participating scientists Samuel Hammer, Christoph Schönherr, Christl Facklam, Ingeborg Levin Abstract Two separate GC instruments were combined via one sample inlet system. The data acquisition and evaluation software was modernised. In addition, it is now possible to determine molecular hydrogen mixing ratios. The rebuilding led to higher measurement precision and a reduction of sample volume and analysis time, both by a factor of two, and the data output is now homogenised for all sample components. Background The radiative forcing due to anthropogenic Greenhouse Gases released into the atmosphere accounts for approximately 1.5 W/m 2 and is therefore the main contributor to global warming [Hansen et al. , n.d.]. Long term greenhouse gas records of high quality are important to determine the temporal change of these trace gases. Combined with isotopic data and regional or global models, the respective budgets can be investigated. In combination with 222 Rn data, local source and sink studies for greenhouse gases can be carried out. Funding This PhD work is funded by the EU projects TCOS - Siberia and CarboEurope-IP. Methods and results In order to couple the GCs by connecting the sample loops of both GCs in series, it was necessary to rebuild the sample inlet system. In addition, the capacity for flask sample measurements was doubled using a separate flask valve. It is now possible to measure twelve flasks within one sequence. To improve the CO reproducibility, a dedicated system of a backflush valve and resistances was developed and successfully installed. Along with the installation of these additional valves, the electronics devices were improved. The two former separate data acquisition systems were replaced by a new, state of the art, ChemStation Chromatography software. The rebuilding led to reduced sample volume and analysis time, which is particularly important for flask measurements. For the semicontinuous measurements in Heidelberg we gained a homogenised dataset. Since the rebuilding of the GC it is possible to determine H2 mixing ratios without further needs. The combined instrument now performs measurements of CO2, CH4, CO, N2O, SF6 and H2 every five minutes. Outside air is measured semi-continuously via two separate air intake lines, each of which is sampled at least once every 30 minutes. An example of the time series and the correlations between the different gas species is given in Figure 2.62. Figure 2.62: Half hourly mixing ratios of CO2, CO, CH4, N2O and H2 in Heidelberg. SW and SE mark the south-west and south-east air intake lines. Additionally 222 Rn daughter concentration and meteorological parameters are shown. Outlook/Future work It is now planned to apply the radon tracer method to the continuous H2 data to assess the sink strength of local soils. Furthermore, a detailed study on the vertical H2 profile in soil air is planned to be performed by a diploma student. The long and extensive N2O records from worldwide monitoring stations will be analysed in a simple 2D model (Naegler, article 2.7.2 this issue) to improve our understanding of the global N2O budget.
2.7. CARBON CYCLE GROUP 111 2.7.4 Investigating CO2, CO and Fossil Fuel CO2 in Heidelberg Participating scientists Christoph Schönherr, Samuel Hammer, Bernd Kromer, Ulrike Gamnitzer, Ingeborg Levin Abstract In order to calibrate CO as a proxy for fossil fuel CO2 (CO2(fossil)), atmospheric CO mixing ratios in Heidelberg are being related to (CO2(fossil)) mixing ratios derived from 14 CO2 measurements. For extension of these investigations to sites without continuous gas chromatographic measurements, a device for integrated air sampling in a large bag was set up and tested. Figure 2.63: Integrated samples of CO2, CO, and 14 CO2 taken in Heidelberg for determination of the ratio CO/CO2(fossil). Blue symbols represent winter months, red symbols summer months; dotted lines are background mixing ratios. (a) Average CO2(total) mixing ratios during the respective sampling periods. (b) Same as (a), but for CO mixing ratios. (c) 14 CO2 depletions of the integrated samples, relative to the continental background. (d) CO2(fossil) mixing ratio as calculated from the CO2(total) mixing ratio and the 14 CO2 depletion. (e) CO/CO2(fossil) ratios for each sample, and the average ratio for all samples (solid black line). Background The global atmospheric mixing ratio of CO2 has been rising from about 280 ppm at the beginning of the 19th century to 378 ppm by the end of 2004, mainly due to the combustion of fossil fuels. This influences the Earth’s climate at present and very likely in the future. In order to estimate fluxes of CO2 into the atmosphere, it is necessary to separate the share originating from fossil fuel combustion. This can be achieved by radiocarbon ( 14 C) observations [Levin et al. , 2003], or by observation of another proxy, like carbon monoxide [Gamnitzer, 2003]. This proxy then has to be calibrated first by parallel 14 C measurements. Methods and results In a first part of my Diploma Thesis, the local gas chromatographic system (GC) was modernised for easier operation and more convenient data output. Second, using CO and 14 CO2 data from the years 2001 to 2005, the CO/CO2(fossil) ratio for Heidelberg was studied. Samples taken during atmospheric inver- sion situations (events) with high local emissions signals yielded CO/CO2(fossil)=(1.06±0.33)%. Weekly and two-weekly integrated 14 CO2 samples influenced by a larger catchment area yielded a mean CO/CO2(fossil) ratio of (1.33 ± 0.29) %. Both methods can be used to assess fossil fuel CO2 for differently sized catchment areas. For determination of CO/CO2(fossil) at sites without continuous GC measurements, a device for integrated air sampling was set up and tested. This device is suited for non-biased sampling of CO2, CO, CH4, N2O, and SF6 during one week. Outlook/Future work The devices for integrated air sampling will now be set up in Paris and Krakow in the frame of the CarboEurope-IP to be run in parallel to integrated 14 CO2 measurements, in order to determine the regional CO/CO2(fossil) ratio with different emission characteristics. Main publication: Schönherr [2005]
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Institut für Umweltphysik und Arbe
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Contents 1 Introduction/Overview of
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CONTENTS 7 3.2.1 Glaciological pilo
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Introduction In Heidelberg, environ
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Overview Summary Atmospheric resear
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2.3. RADIATIVE TRANSFER 45 2.3 Radi
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2.3. RADIATIVE TRANSFER 47 Funding
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2.3. RADIATIVE TRANSFER 53 Rothman,
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Forschungsstelle “Radiometrie”
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7.3. PHD THESES 217 PhD Theses Baye
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7.5. INVITED TALKS 221 Invited Talk
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7.5. INVITED TALKS 223 Pundt, I. 20
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