  Determination of isotopic fractionation delta13C of methane from ground-based FTIR observations performed at the JungfraujochDuchatelet, Pierre  ; Mahieu, Emmanuel ; et alPoster (2009, April) Atmospheric methane (CH4) is a strong greenhouse gas that has important chemical impacts on both the troposphere and the stratosphere. In the troposphere, oxidation of methane is a major regulator of OH ... [more ▼] Atmospheric methane (CH4) is a strong greenhouse gas that has important chemical impacts on both the troposphere and the stratosphere. In the troposphere, oxidation of methane is a major regulator of OH and is a source of formaldehyde, carbon monoxide and hydrogen. In the stratosphere, CH4 plays a central role (i), due to its contribution to the stratospheric water vapor budget, and (ii), as a sink for chlorine atoms which reduces the rate of stratospheric ozone depletion. Because the different sources of methane (natural and anthropogenic like wetlands, rice paddies, termites, natural gas escape, biomass burning, etc) have distinct 13C/12C ratios (usually reported in “delta” notation δ13C), measurements of atmospheric 13CH4 content, in addition to those of the main isotopologue (12CH4), can be used to investigate individual source strengths as well as their spatial and temporal distributions. Characterization of the isotopic fractionation of methane is therefore important, for example, to help models constrain estimates of the global methane budget. However, experimental data for the 13C/12C isotope ratio are sparse. The currently accepted average value of δ13C in atmospheric methane is about -47‰ (Platt et al., 2004). The first goal of this work is to develop and to characterize (in terms of information content and error budget) an original retrieval approach to derive 13CH4 columns from ground-based Fourier transform infrared (FTIR) spectra recorded at the International Scientific Station of the Jungfraujoch (ISSJ; 46.5°N, 8.0°E, 3580m a.s.l., Swiss Alps). The retrieval strategy is based on a Tikhonov L1 approach which has been originally developed for 12CH4 by Sussmann et al. (2008) [see also contributions by Sussmann et al. to this conference (EGU2009-7869)]. In order to validate our 13CH4 products, comparisons with satellite ACE-FTS (Atmospheric Chemistry Experiment - Fourier Transform Spectrometer) measurements are performed. Then, atmospheric δ13C ratios derived from the FTIR measurements will be compared to values published in the literature and critically discussed. References: Platt, U., W. Allan and D. Lowe, Hemispheric average Cl atom concentration from 13C/12C ratios in atmospheric methane, Atmos. Chem. Phys., 4, 2393-2399, 2004. Sussmann, R., Forster, F., Borsdorff, T., et al.: Satellite validation of column-averaged methane on global scale: ground-based data from 15 FTIR stations versus last generation ENVISAT/SCIAMACHY retrievals, IGAC 10th International Conference, Annecy, France, 7-12 Sep 2008. [less ▲] Detailed reference viewed: 68 (11 ULg) Validation of SCIAMACHY CH4 scientific products using ground-based FTIR measurements; ; et al Poster (2008, September) In the framework of the past EVERGREEN project, the development of three scientific algorithms, namely WFM-DOAS (henceforward called WFMD), IMAP-DOAS (henceforward called IMAP) and IMLM, commenced in ... [more ▼] In the framework of the past EVERGREEN project, the development of three scientific algorithms, namely WFM-DOAS (henceforward called WFMD), IMAP-DOAS (henceforward called IMAP) and IMLM, commenced in order to retrieve the total column amounts of key atmospheric trace gases, including CH4, from SCIAMACHY nadir observations in its near-infrared channels. Since then, the retrieval products of these three algorithms, have undergone serious improvements. At key phases in their development, the products have been validated by using a network of ground-based FTIR instruments. Parallel with the improved SCIAMACHY data, the FTIR groups have taken steps to optimise and harmonise their own datasets and as such the different validation efforts always used the state-of-the-art FTIR dataset. Here we present an overview of the evolution of the CH4 algorithms by re-validating the data, using the same FTIR dataset (as developed under the UFTIR project) for all algorithm versions. [less ▲] Detailed reference viewed: 111 (6 ULg)Satellite validation of column-averaged methane on global scale: ground-based data from 15 FTIR stations versus last generation ENVISAT/SCIAMACHY retrievals; ; et al Poster (2008, September) Previous work has shown that the precision of ground-based mid-infrared (MIR) FTIR spectrometry is sufficient to detect day-to-day variability of columnar methane, while first retrievals from ENVISAT ... [more ▼] Previous work has shown that the precision of ground-based mid-infrared (MIR) FTIR spectrometry is sufficient to detect day-to-day variability of columnar methane, while first retrievals from ENVISAT/SCIAMACHY (channel 8) satellite measurements were impacted by a significant time-dependent bias due to detector icing. This prevented insight into true methane temporal variability at that time. The goal of our updated study is to investigate the precision of the last generation (channel 6) SCIAMACHY retrievals IMAP-DOAS v49 and WFM-DOAS v1.0 in comparison to retrievals from ground-based MIR measurements of the European FTIR network. We first briefly discuss the origin and magnitude of the natural variability of columnar methane. Subsequently, our study investigates all factors which can be optimized to improve precision of ground-based MIR-FTIR retrievals of columnar methane. This includes an optimized Tikhonov-type regularization tuned in a way to minimize the diurnal variability of retrieved columnar methane. We also discuss ways to select and average individual-pixel satellite data in order to reflect true day-to-day variability and make them comparable to ground-based data. [less ▲] Detailed reference viewed: 46 (13 ULg)Measured and modeled trends of stratospheric Cly and Fy column amounts in the northern hemisphere; ; et al Poster (2008, July) The german HGF virtual institute PEP (Pole-Equator-Pole) has been established in 2004 in order to investigate the variability of atmospheric trace constituents along a north-south transection. Within PEP ... [more ▼] The german HGF virtual institute PEP (Pole-Equator-Pole) has been established in 2004 in order to investigate the variability of atmospheric trace constituents along a north-south transection. Within PEP the HGF centres AWI and FZK as well as the german Universities of Bremen, Karlsruhe and Potsdam combine their knowledge and capabilities in ground-based measurements and global and regional modelling of atmospheric trace constituents and aerosols. Here we present results of long-term measurements of the stratospheric column of HCl, ClONO2, HF, and O3 obtained at the different PEP stations in the northern hemisphere and in addtion at Jungfraujoch. All stations are affiliated to the NDACC (Network for the Detection of Atmospheric Composition Change). The measured time series are compared with long-term model calculations performed with a state of the art 2-D model of the University of Bremen and the 3-D CTM KASIMA. Please note, that the lowest altitude for the determination of the total columns is about 7 km leading to a slight underestimation w.r.t. the measurements. [less ▲] Detailed reference viewed: 36 (6 ULg) |
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