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See detailRetrievals of ethane from ground-based high-resolution FTIR solar observations with updated line parameters: determination of the optimum strategy for the Jungfraujoch station.
Bader, Whitney ULg; Perrin, Agnès; Jacquemart, David et al

in Geophysical Research Abstracts (2012), 14(EGU2012-9126),

Ethane (C2H6) is the most abundant Non-Methane HydroCarbon (NMHC) in the Earth’s atmosphere, with a lifetime of approximately 2 months. C2H6 has both anthropogenic and natural emission sources such as ... [more ▼]

Ethane (C2H6) is the most abundant Non-Methane HydroCarbon (NMHC) in the Earth’s atmosphere, with a lifetime of approximately 2 months. C2H6 has both anthropogenic and natural emission sources such as biomass burning, natural gas loss and biofuel consumption. Oxidation by the hydroxyl radical is by far the major C2H6 sink as the seasonally changing OH concentration controls the strong modulation of the ethane abundance throughout the year. Ethane lowers Cl atom concentrations in the lower stratosphere and is a major source of peroxyacetyl nitrate (PAN) and carbon monoxide (by reaction with OH). Involved in the formation of tropospheric ozone and in the destruction of atmospheric methane through changes in OH, C2H6 is a non-direct greenhouse gas with a net-global warming potential (100-yr horizon) of 5.5. The retrieval of ethane from ground-based infrared (IR) spectra is challenging. Indeed, the fitting of the ethane features is complicated by numerous interferences by strong water vapor, ozone and methane absorptions. Moreover, ethane has a complicated spectrum with many interacting vibrational modes and the current state of ethane parameters in HITRAN (e.g. : Rothman et al., 2009, see http://www.hitran.com) was rather unsatisfactory in the 3 µm region. In fact, PQ branches outside the 2973–3001 cm-1 range are not included in HITRAN, and most P and R structures are missing. New ethane absorption cross sections recorded at the Molecular Spectroscopy Facility of the Rutherford Appleton Laboratory (Harrison et al., 2010) are used in our retrievals. They were calibrated in intensity by using reference low-resolution spectra from the Pacific Northwest National Laboratory (PNNL) IR database. Pseudoline parameters fitted to these ethane spectra have been combined with HITRAN 2004 line parameters (including all the 2006 updates) for all other species encompassed in the selected microwindows. Also, the improvement brought by the update of the line positions and intensities of methyl chloride (CH3Cl) in the 3.4 m region (Bray et al., 2011) will be quantified. The ethane a priori volume mixing ratio (VMR) profile and associated covariance are based on synthetic data from the chemical transport model (CTM) of the University of Oslo. In this contribution, we will present updated ethane total and tropospheric column retrievals, using the SFIT-2 algorithm (v3.91) and high-resolution Fourier Transform Infrared (FTIR) solar absorption observations recorded with a Bruker 120HR instrument, at the high altitude research station of the Jungfraujoch (46.5°N, 8°E, 3580 m asl), within the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). We will characterize three microwindows encompassing the strongest ethane features after careful selection of a priori VMR profiles, spectroscopic parameters, accounting at best for all interfering species. We will then present the retrieval strategy representative of the best combination of those three characterized micro-windows in order to minimize the fitting residuals while maximizing the information content, the precision and the reliability of the retrieved product. The long-term C2H6 column time series will be produced using the Jungfraujoch observational database. Comparisons with synthetic data produced by two chemical transport model (CHASER and the one of the University of Oslo) will also be presented and analyzed, aiming at the determination and interpretation of long-term trends and interannual variations of ethane at Northern mid-latitudes. [less ▲]

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See detailTrend analysis of greenhouse gases over Europe measured by a network of ground-based remote FTIR instruments
Gardiner, Tom; Forbes, A.; De Mazière, Martine et al

in Atmospheric Chemistry and Physics (2008), 8(22), 6719-6727

This paper describes the statistical analysis of annual trends in long term datasets of greenhouse gas measurements taken over ten or more years. The analysis technique employs a bootstrap resampling ... [more ▼]

This paper describes the statistical analysis of annual trends in long term datasets of greenhouse gas measurements taken over ten or more years. The analysis technique employs a bootstrap resampling method to determine both the long-term and intra-annual variability of the datasets, together with the uncertainties on the trend values. The method has been applied to data from a European network of ground-based solar FTIR instruments to determine the trends in the tropospheric, stratospheric and total columns of ozone, nitrous oxide, carbon monoxide, methane, ethane and HCFC-22. The suitability of the method has been demonstrated through statistical validation of the technique, and comparison with ground-based in-situ measurements and 3-D atmospheric models. [less ▲]

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See detailAdvanced exploitation of ground-based Fourier transform infrared observations for tropospheric studies over Europe: achievements of the UFTIR project
De Mazière, Martine; Vigouroux, Corinne; Blumenstock, Thomas et al

in Geophysical Research Abstracts (2006), 8

Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including information about their vertical ... [more ▼]

Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including information about their vertical distributions in the troposphere and the stratosphere. Such observations have regularly been made since many years as a contribution to the NDSC (Network for the Detection of Stratospheric Change). They are the only ground-based remote sensing observations available nowadays that carry information about key atmospheric trace species in the free troposphere, among which the most important greenhouse gases. The European UFTIR project (Time series of Upper Free Troposphere observations from a European ground-based FTIR network, http://www.nilu.no/uftir) has focused on maximizing the information content of FTIR long-term monitoring data of some direct and indirect greenhouse gases (CH4, N2O, O3,HCFC-22, and CO and C2H6, respectively). The UFTIR network includes six NDSC stations in Western Europe, covering the polar to subtropical regions. At several stations of the network, the observations span more than a decade. Existing spectral time series have been reanalyzed according to a common optimized retrieval strategy, in order to derive distinct tropospheric and stratospheric abundances of the abovementioned target gases. A bootstrap resampling method has been implemented to evaluate trends of the tropospheric and total burdens of the target gases, including their uncertainties. In parallel, simulations of the target time series have been made with the Oslo CTM2 model: comparisons between the model results and the observations provide valuable information to improve the model, and in particular, to optimize emission estimates that are used as inputs to the model simulations, and to explain the observed trends. The final results of the project will be presented, and ways to proceed will be discussed. [less ▲]

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See detailThe exploitation of ground-based Fourier transform infrared observations for the evaluation of tropospheric trends of greenhouse gases over Europe
De Mazière, Martine; Vigouroux, Corinne; Gardiner, Tom et al

in Environmental Sciences (2005), 2(2-3), 283-293

Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including non-CO2 greenhouse gases. Such ... [more ▼]

Solar absorption measurements using Fourier transform infrared (FTIR) spectrometry carry information about the atmospheric abundances of many constituents, including non-CO2 greenhouse gases. Such observations have regularly been made for many years as a contribution to the Network for the Detection of Stratospheric Change (NDSC). They are the only ground-based remote sensing observations available nowadays that carry information about a number of greenhouse gases in the free troposphere. This work focuses on the discussion of the information content of FTIR long-term monitoring data of some direct and indirect greenhouse gases (CH4, N2O, O3 and CO and C2H6, respectively), at six NDSC stations in Western Europe. This European FTIR network covers the polar to subtropical regions. At several stations of the network, the observations span more than a decade. Existing spectral time series have been reanalyzed according to a common optimized retrieval strategy, in order to derive distinct tropospheric and stratospheric abundances for the above-mentioned target gases. A bootstrap resampling method has been implemented to evaluate trends of the tropospheric burdens of the target gases, including their uncertainties. In parallel, simulations of the target time series are being made with the Oslo CTM2 model: comparisons between the model results and the observations provide valuable information to improve the model and, in particular, to optimize emission estimates that are used as inputs to the model simulations. The work is being performed within the EC project UFTIR. The paper focuses on N2O for which the first trend results have been obtained. [less ▲]

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