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See detailLong-term evolution and seasonal modulation above Jungfraujoch (46.5°N, 8.0°E): Optimisation of the retrieval strategy, comparison with model and independant observations
Bader, Whitney ULg; Stavrakou, T; Muller, J-F et al

in Atmospheric Measurement Techniques. Papers in Open Discussion (2014), 7

Methanol (CH3OH) is the second most abundant organic compound in the Earth's atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and ... [more ▼]

Methanol (CH3OH) is the second most abundant organic compound in the Earth's atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and upper tropospheric-lower stratospheric partial columns derived from the analysis of high resolution Fourier transform infrared solar spectra recorded at the Jungfraujoch station (46.5° N, 3580 m a.s.l.). The retrieval of methanol is very challenging due to strong absorptions of ozone in the region of the selected υ8 band of CH3OH. Two wide spectral intervals have been defined and adjusted in order to maximize the information content. Methanol does not exhibit a significant trend over the 1995–2012 time period, but a strong seasonal modulation characterized by maximum values and variability in June–July, minimum columns in winter and a peak-to-peak amplitude of 130%. In situ measurements performed at the Jungfraujoch and ACE-FTS occultations give similar results for the methanol seasonal variation. The total and lower tropospheric columns are also compared with IMAGESv2 model simulations. There is no systematic bias between the observations and IMAGESv2 but the model underestimates the peak-to-peak amplitude of the seasonal modulations. [less ▲]

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See detailSeeking for causes of recent methane increase: comparison between GEOS-Chem tagged simulations and FTIR column measurements above Jungfraujoch
Bader, Whitney ULg; Bovy, Benoît ULg; Wecht, K et al

Poster (2014, May)

Atmospheric CH4 reached 260% of the pre-industrial level (~700 ppb) due to increased emissions from anthropogenic sources. Globally averaged CH4 reached a new high of 1819 ± 1 ppb in 2012, an increase of ... [more ▼]

Atmospheric CH4 reached 260% of the pre-industrial level (~700 ppb) due to increased emissions from anthropogenic sources. Globally averaged CH4 reached a new high of 1819 ± 1 ppb in 2012, an increase of 6 ppb with respect to the previous year (WMO, Greenhouse gas Bulletin N.9, 2013). CH4 above Jungfraujoch increases at 0.53±0.19%/year during the late 90s to stabilize and reach a non significant trend from 2000 to 2005. Since 2006, atmospheric methane has been continuously increasing with a rate of 0.19±0.05 %/year. The attribution of this increase to any CH4 source is difficult since the current network is insufficient to characterize emissions by region and source process, emphasizing the need for source-tagged model simulations as it should provide us information on processes causing the increase of atmospheric methane since 2005/2006. [less ▲]

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See detailLong-term evolution and seasonal modulation above Jungfraujoch (46.5°N, 8.0°E): Optimisation of the retrieval strategy, comparison with model and independant observations
Bader, Whitney ULg; Stavrakou, J; Muller, J-F et al

Poster (2014, May)

Methanol (CH3OH) is the second most abundant organic compound in the Earth’s atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and ... [more ▼]

Methanol (CH3OH) is the second most abundant organic compound in the Earth’s atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and upper tropospheric-lower stratospheric partial columns derived from the analysis of high resolution Fourier transform infrared solar spectra recorded at the Jungfraujoch station (46.5°N, 3580 m a.s.l.). The retrieval of methanol is very challenging due to strong absorptions of ozone in the region of the selected 8 band of CH3OH. Two wide spectral intervals have been defined and adjusted in order to maximize the information content. Methanol does not exhibit a significant trend over the 1995-2012 time period, but a strong seasonal modulation characterized by maximum values and variability in June-July, minimum columns in winter and a peak-to-peak amplitude of 130 %. In situ measurements performed at the Jungfraujoch and ACE-FTS occultations give similar results for the methanol seasonal variation. The total and lower tropospheric columns are also compared with IMAGESv2 model simulations. There is no systematic bias between the observations and IMAGESv2 but the model underestimates the peak-to-peak amplitude of the seasonal modulations. [less ▲]

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See detailSpectrometric monitoring of atmospheric carbon tetrafluoride (CF4) above the Jungfraujoch station since 1989: evidence of continued increase but at a slowing rate
Mahieu, Emmanuel ULg; Zander, Rodolphe ULg; Toon, G. C. et al

in Atmospheric Measurement Techniques (2014), 7

The long-term evolution of the vertical column abundance of carbon tetrafluoride (CF4) above the high-altitude Jungfraujoch station (Swiss Alps, 46.5° N, 8.0° E, 3580 m a.s.l.) has been derived from the ... [more ▼]

The long-term evolution of the vertical column abundance of carbon tetrafluoride (CF4) above the high-altitude Jungfraujoch station (Swiss Alps, 46.5° N, 8.0° E, 3580 m a.s.l.) has been derived from the spectrometric analysis of Fourier transform infrared solar spectra recorded at that site between 1989 and 2012. The investigation is based on a multi-microwindow approach, two encompassing pairs of absorption lines belonging to the R-branch of the strong ν3 band of CF4 centered at 1283 cm−1, and two additional ones to optimally account for weak but overlapping HNO3 interferences. The analysis reveals a steady accumulation of the very long-lived CF4 above the Jungfraujoch at mean rates of (1.38 ± 0.11) × 1013 molec cm−2 yr−1 from 1989 to 1997, and (0.98 ± 0.02) × 1013 molec cm−2 yr−1 from 1998 to 2012, which correspond to linear growth rates of 1.71 ± 0.14 and 1.04 ± 0.02% yr−1 respectively referenced to 1989 and 1998. Related global CF4 anthropogenic emissions required to sustain these mean increases correspond to 15.8 ± 1.3 and 11.1 ± 0.2 Gg yr−1 over the above specified time intervals. Findings reported here are compared and discussed with respect to relevant northern mid-latitude results obtained remotely from space and balloons as well as in situ at the ground, including new gas chromatography mass spectrometry measurements performed at the Jungfraujoch since 2010. [less ▲]

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See detailOverview of the geophysical data derived from long-term FTIR monitoring activities at the Jungfraujoch NDACC site (46.5ºN) and the PYGCHEM project
Mahieu, Emmanuel ULg; Bovy, Benoît ULg; Bader, Whitney ULg et al

Poster (2013, May 07)

We present an overview of the geophysical data deduced from long-term monitoring activities conducted at the Jungfraujoch station by the University of Liège. Typical results and trend investigations are ... [more ▼]

We present an overview of the geophysical data deduced from long-term monitoring activities conducted at the Jungfraujoch station by the University of Liège. Typical results and trend investigations are presented for hydrogen chloride (HCl) and carbonyl sulfide (OCS). We further display and briefly describe time series for new target gases, namely methanol (CH3OH) and HCFC-142b. We also show some preliminary results for ammonia (NH3) and peroxyacetyl nitrate (PAN). Finally, we present the PyGChem project, a Python interface to the GEOS-Chem model currently under development at ULg. [less ▲]

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See detailEvolution of methanol (CH3OH) above the Jungfraujoch station (46.5°N) : Variability, seasonal modulation and long-term trend.
Bader, Whitney ULg; Mahieu, Emmanuel ULg; Lejeune, Bernard ULg et al

Poster (2013, April 09)

Methanol (CH3OH) is the second most abundant organic compound in the Earth’s atmosphere with concentrations close to a few ppbv, after methane, despite a short lifetime of a few days (Jacob et al., 2005 ... [more ▼]

Methanol (CH3OH) is the second most abundant organic compound in the Earth’s atmosphere with concentrations close to a few ppbv, after methane, despite a short lifetime of a few days (Jacob et al., 2005). Natural sources of CH3OH include plant growth, oceans, decomposition of plant matter, oxidation of methane and other VOCs,. . . while anthropogenic sources are from vehicles, industry,. . . biomass burning completes the emission budget. The main sink is the oxidation by hydroxyl radical, leading to the formation of carbon monoxide (CO) and formaldehyde (H2CO). The retrieval of methanol is very challenging due to the presence of strong absorption of ozone and its isotopologues in addition to water vapour and carbon dioxide in the region of the selected strong nu8 band of CH3OH. First retrievals from satellite observations using the Atmospheric Chemistry Experiment infrared Fourier Transform Spectrometer (ACE-FTS) on board the SCISAT satellite have been performed by Dufour et al. (2007 and references therein) using a spectral interval going from 995.5 to 1008.3 cm-1. In 2009, first retrievals from a ground-based FTS, using spectra recorded at Kitt Peak (31.9°N) and a window going from 992 to 999 cm-1 have been reported by Rinsland et al. (2009), followed by Vigouroux et al. (2012 and references therein) who used yet another spectral interval going from 1029 to 1037cm-1. From those former retrieval strategies and also considering the Mahieu et al. (2012) contribution, we redefined our spectral intervals to maximize the information content. Indeed, our first window, starting from 992 to 1008.3 cm-1, is issued from the merge of Rinsland et al. and Dufour et al. windows while our second, going from 1029 to 1037 cm-1, is the one used by Vigouroux et al.With this new combination of windows, we were able to enlarge the range of zenith angles providing robust results while maintaining good correlation between our two windows; this also resulted in an improvement of the fitting residuals and of the information content. We used the 2008 HITRAN compilation (Rothman et al., 2009) for spectroscopic parameters. However, systematic residuals still remain in the 1033 cm-1 region which are attributed to unsatisfactory line parameters for methanol. New cross sections recorded at the Molecular Spectroscopy Facility of the Rutherford Appleton Laboratory (Harrison et al. 2012) and calibrated in intensity by using the reference spectra from the Pacific Northwest National Laboratory (PNNL) IR database will be tested as soon as converted into pseudolines. In this work, we will present the first long-term time series of methanol total columns, resulting from the implementation of our new retrieval strategy. All retrievals have been performed with the SFIT2 algorithm (v 3.91) (Rinsland et al., 1998) using a series of about 7 000 spectra recorded between 1995 and 2012, with zenith angles between 60 and 85°. These solar absorption observations have been recorded with a high-resolution FTIR Bruker 120HR instrument, at the high altitude 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). [less ▲]

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See detailComparison of ground-based remote sensing and in-situ observations of CO, CH4 and O3, accounting for representativeness uncertainty
Henne, S.; Steinbacher, M.; Mahieu, Emmanuel ULg et al

Conference (2013, April)

The EC project NORS (Demonstration Network Of ground-based Remote Sensing Observations in support of the GMES Atmospheric Service) aims at demonstrating the value of ground-based remote sensing data for ... [more ▼]

The EC project NORS (Demonstration Network Of ground-based Remote Sensing Observations in support of the GMES Atmospheric Service) aims at demonstrating the value of ground-based remote sensing data for quality assessment and improvement of the GMES products. As part of NORS CO, CH4, O3 and NO2 tropospheric products as obtained by ground-based remote sensing within the Network for the Detection of Atmospheric Composition Change (NDACC) are compared to continuous surface in-situ measurements that are reported on common international reference scales within the Global Atmospheric Watch (GAW) Programme. However, a direct comparison between the different methods is hindered by different sampling volumes, introducing uncertainties due to representativeness. Here we present a novel method that utilises high-resolution, backward Lagrangian particle dispersion modelling to characterise the transport history of different sampling volumes. Sampling volumes are defined as infinitesimally small point volumes for the in-situ observations and as separate profile segments with horizontal and vertical extent for the remote sensing observations. The characterisation is then used (a) to filter times for which a direct comparison between in-situ and remote sensing data is unfavourable (large representativeness uncertainty) and (b) to construct vertical profiles from the in-situ observations, taking additional information from large scale atmospheric composition models into account. These so called “in-situ” profiles are supposed to be more comparable to the remote sensing profile as the surface value itself, while conserving the high accuracy information of the latter and projecting it onto the profile. Therefore, these profiles allow for a more direct comparison and validation of the remotely sensed profiles. The technique was first applied at two of the four NORS demonstration sites (Jungfraujoch, Switzerland and Izana, Spain) and to the comparison of remote sensing Fourier-transform infrared spectrometer (FTIR) measurements of CO, CH4, and O3 with the responding in-situ observations. While previous studies generally showed good agreement between the two kinds of observation, considerable amounts of scatter were evident. Selecting only situations with relatively small representativeness uncertainty reduces this scatter. Folding the “in-situ” profiles with the averaging kernels of the FTIR retrieval gives a more realistic comparison result that is not influenced by any a-priori assumptions. Results are also discussed with respect to season, time of day and weather type. [less ▲]

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See detailFirst retrievals of HCFC-142b from ground-based high resolution FTIR solar observations: application to high altitude Jungfraujoch spectra
Mahieu, Emmanuel ULg; O'Doherty, Simon; Reimann, Stefan et al

in Geophysical Research Abstracts (2013), 15

Hydrofluorocarbons (HCFCs) are the first substitutes to the long-lived ozone depleting halocarbons, in particular the chlorofluorocarbons (CFCs). Given the complete ban of the CFCs by the Montreal ... [more ▼]

Hydrofluorocarbons (HCFCs) are the first substitutes to the long-lived ozone depleting halocarbons, in particular the chlorofluorocarbons (CFCs). Given the complete ban of the CFCs by the Montreal Protocol, its Amendments and Adjustments, HCFCs are on the rise, with current rates of increase substantially larger than at the beginning of the 21st century. HCFC-142b (CH3CClF2) is presently the second most abundant HCFC, after HCFC-22 (CHClF2). It is used in a wide range of applications, including as a blowing foam agent, in refrigeration and air-conditioning. Its concentration will soon reach 25 ppt in the northern hemisphere, with mixing ratios increasing at about 1.1 ppt/yr [Montzka et al., 2011]. The HCFC-142b lifetime is estimated at 18 years. With a global warming potential of 2310 on a 100-yr horizon, this species is also a potent greenhouse gas [Forster et al., 2007]. First space-based retrievals of HCFC-142b have been reported by Dufour et al. [2005]. 17 occultations recorded in 2004 by the Canadian ACE-FTS instrument (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer, onboard SCISAT-1) were analyzed, using two microwindows (1132.5–1135.5 and 1191.5–1195.5 cm-1). In 2009, Rinsland et al. determined the HCFC-142b trend near the tropopause, from the analysis of ACE-FTS observations recorded over the 2004–2008 time period. The spectral region used in this study extended from 903 to 905.5 cm-1. In this contribution, we will present the first HCFC-142b measurements from ground-based high-resolution Fourier Transform Infrared (FTIR) solar spectra. We use observations recorded at the high altitude station of the Jungfraujoch (46.5°N, 8°E, 3580 m asl), with a Bruker 120HR instrument, in the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). The retrieval of HCFC-142b is very challenging, with simulations indicating only weak absorptions, lower than 1% for low sun spectra and current concentrations. Among the four microwindows tested, the region extending from 900 to 906 cm-1 proved to be the most appropriate, with limited interferences, in particular from water vapor. A total column time series spanning the 2004-2012 time period will be presented, analyzed and critically discussed. After conversion of our total columns to concentrations, we will compare our results with in situ measurements performed in the northern hemisphere by the AGAGE network. [less ▲]

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See detailLong-term trends of NO above northern mid-latitudes as inferred from Jungfraujoch, HALOE and ACE-FTS solar observations
Demoulin, Philippe ULg; Mahieu, Emmanuel ULg; Servais, Christian ULg et al

Poster (2012, August 27)

Routine FTIR solar observations are performed by the University of Liège at the Jungfraujoch station (Swiss Alps, 3580 m altitude, NDACC station) since 1985. The analysis of the recorded spectra allows to ... [more ▼]

Routine FTIR solar observations are performed by the University of Liège at the Jungfraujoch station (Swiss Alps, 3580 m altitude, NDACC station) since 1985. The analysis of the recorded spectra allows to derive total and partial columns of more than 20 different atmospheric gases. Among them, gases belonging to the total reactive nitrogen NOy (NO, NO2, HNO3 and ClONO2), to the total inorganic chlorine Cly (HCl and ClONO2) and to the total inorganic fluorine Fy (HF and COF2) families. In this communication, budgets of these gas families are investigated, and their short term, seasonal and inter-annual variations as well as their long-term trends are determined for the time period ranging from the mid-1980s up to the end of 2011. We also investigate the evolution of the same gases, when available, derived from ground-based UV-vis (1990-present) and from HALOE (1991-2004) and ACE-FTS (2004-present) satellite observations. We evaluate the consistency between the trends characterizing these various species, as deduced from the ground- and space-based time series. [less ▲]

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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

Poster (2012, August)

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. The retrieval of ethane from ground-based infrared spectra is challenging. Indeed, ethane has a complicated spectrum with many interacting vibrational modes and the current state of ethane parameters in HITRAN (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. 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. We evaluated the impact on spectral residuals induced by the update of two O3 lines (encompassed in the PQ3 µ-window) corrected by P. Chelin (LPMA, Paris, France). We also quantified the improvement brought by the update of the line positions and intensities of methyl chloride (CH3Cl) in the 3.4 µm region (Bray et al., 2011). The ethane a priori volume mixing ratio (VMR) profile and associated covariance are based on synthetic data from CHASER 3-D chemical transport model (CTM). In this contribution, we will present updated ethane (total) 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). Comparisons with synthetic data produced by two chemical transport models (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 detailRetrievals of ethane from groundbased highresolution 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

Scientific conference (2012, June 01)

Ethane (C2H6) is the most abundant Non-Methane HydroCarbon (NMHC) in the Earth’s atmosphere, with a lifetime of approximately 2 months. Its main sources are biomass burning, natural gas loss and biofuel ... [more ▼]

Ethane (C2H6) is the most abundant Non-Methane HydroCarbon (NMHC) in the Earth’s atmosphere, with a lifetime of approximately 2 months. Its main sources are biomass burning, natural gas loss and biofuel consumption. Oxidation by the hydroxyl radical is the major C2H6 sink as it controls its strong modulation throug the year. C2H6 is involved in the formation of tropospheric O3 and in the destruction of atmospheric methane through changes in OH. C2H6 is an indirect greenhouse gas with a net-global warming potential of 5.5 (100-yr horizon). Updates of retrieval parameters such as the spectroscopic linelists have been recently published. We will therefore characterize three µ-windows encompassing the strongest C2H6 features after careful selection of these new parameters, accounting at best for all interfering species. The aim is to lessen the fitting residuals while maximizing the information content, the precision and the reliability of the retrieved product. We will present updated C2H6 total and tropospheric column time series, using the SFIT-2 algorithm (v3.91) and high-resolution Fourier Transform Infrared (FTIR) solar absorption spectra recorded with a Bruker 120HR instrument, at the high altitude research station of the Jungfraujoch (46.5°N, 8.0°E, 3580 m asl), within the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, http://www.ndacc.org). Comparisons with synthetic data produced by chemical transport models will also be presented. [less ▲]

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See detailRetrieval of methanol (CH3OH) above the high-altitude Jungfraujoch station (46.5ºN): preliminary total column time series, long-term trend and seasonal modulation
Mahieu, Emmanuel ULg; Bader, Whitney ULg; Bovy, Benoît ULg et al

Poster (2012, June)

Methanol (CH3OH) is a key organic compound in the Earth’s troposphere, with reported concentrations of the order of a few ppbv. It is indeed the second most abundant organic atmospheric compound after ... [more ▼]

Methanol (CH3OH) is a key organic compound in the Earth’s troposphere, with reported concentrations of the order of a few ppbv. It is indeed the second most abundant organic atmospheric compound after methane. Its lifetime is estimated to a few days. Natural sources of CH3OH include plant growth, oceans, decomposition of plant matter, oxidation of methane,… They are complemented by anthropogenic (from vehicles, industry) and biomass burning emissions. Oxidation by the hydroxyl radical is the main sink, leading to the formation of carbon monoxide (CO) and formaldehyde (H2CO). The first reported retrievals of methanol used a microwindow extending from 992 to 999 cm-1 or from 1029 to 1037 cm-1. In both cases, lines of the strong ν8 band of CH3OH were adjusted, accounting for interferences by several isotopologues of ozone and by water vapor. In this contribution, we present first retrievals of CH3OH from observations recorded at the high-altitude station of the Jungfraujoch (46.5°N, 8°E, 3580 m asl), with a Bruker 120HR spectrometer, in the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). A strategy maximizing the information content and combining the 992-999 and 1029-1037 cm-1 domains has been set up and used. A preliminary long-term CH3OH total column time series derived from the Jungfraujoch observational database allows us to investigate the seasonal variation and long-term trend of this species at northern mid-latitudes. [less ▲]

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See detailSeeking for the optimum retrieval strategy of methanol (CH3OH) from ground-based high-resolution FTIR solar observations recorded at the high-altitude Jungfraujoch station (46.5ºN)
Mahieu, Emmanuel ULg; Bader, Whitney ULg; Lejeune, Bernard ULg et al

in Geophysical Research Abstracts (2012), 14

Methanol (CH3OH) is a key organic compound in the Earth’s troposphere, with reported concentrations of the order of a few ppbv. It is indeed the second most abundant organic atmospheric compound after ... [more ▼]

Methanol (CH3OH) is a key organic compound in the Earth’s troposphere, with reported concentrations of the order of a few ppbv. It is indeed the second most abundant organic atmospheric compound after methane (Jacob et al., 2005). The same authors have estimated its lifetime to a few days. Natural sources of CH3OH include plant growth, oceans, decomposition of plant matter, oxidation of methane,. . . They are complemented by anthropogenic (from vehicles, industry) and biomass burning emissions. Oxidation by the hydroxyl radical is the main sink, leading to the formation of carbon monoxide (CO) and formaldehyde (H2CO) (Rinsland et al., 2009; Stavrakou et al., 2011, and references therein). The first retrievals of methanol from ground-based Fourier Transform Infrared (FTIR) spectra have been reported by Rinsland et al. (2009), using spectra recorded at Kitt Peak (31.9ºN) and a microwindow extending from 992 to 999 cm-1. Soon after, Stavrakou et al. (2011) used another spectral interval from 1029 to 1037 cm-1, for methanol retrievals at Reunion Island (21ºS). In both cases, lines of the strong nu8 band of CH3OH were adjusted, accounting for interferences by several isotopologues of ozone and by water vapor. In this contribution, we will present first retrievals of CH3OH from observations recorded at the high-altitude station of the Jungfraujoch (46.5ºN, 8ºE, 3580 m asl), with a Bruker 120HR spectrometer, in the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). We will implement existing retrieval approaches –and possibly additional one(s)– to determine which strategy is the most appropriate for our dry high-altitude site. If successful, a long-term CH3OH total column time series will be produced using the Jungfraujoch observational database, and we will perform preliminary investigations to characterize the seasonal and inter-annual variations of this species at northern mid-latitudes. [less ▲]

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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 detailLong-term trends of a dozen direct greenhouse gases derived from infrared solar absorption spectra recorded at the Jungfraujoch station
Mahieu, Emmanuel ULg; Duchatelet, Pierre; Zander, Rodolphe ULg et al

Poster (2011, November 10)

References Bader, W. et al., Extension of the long-term total column time series of atmospheric methane above the Jungfraujoch station: analysis of grating infrared spectra between 1976 and 1989 ... [more ▼]

References Bader, W. et al., Extension of the long-term total column time series of atmospheric methane above the Jungfraujoch station: analysis of grating infrared spectra between 1976 and 1989, Geophysical Research Abstracts, 13, EGU2011-3391-1, 2011. [http://hdl.handle.net/2268/88180] Duchatelet, P. et al., First retrievals of carbon tetrafluoride (CF4) from ground-based FTIR measurements: production and analysis of the two-decadal time series above the Jungfraujoch, Geophysical Research Abstracts, 13, EGU2011-6413, 2011. [http://hdl.handle.net/2268/90745] Gardiner, T. et al., Trend analysis of greenhouse gases over Europe measured by a network of ground-based remote FTIR instruments, Atmos. Chem. Phys., 8, 6719-6727, 2008. [http://hdl.handle.net/2268/2545] Rodgers, C.D., Characterisation and error analysis of profiles derived from remote sensing measurements, J. Geophys. Res., 95, 5587-5595, 1990. Zander, R. et al., Our changing atmosphere: Evidence based on long-term infrared solar observations at the Jungfraujoch since 1950, Sci. Total Environ., 391, 184-195, 2008. [http://hdl.handle.net/2268/2421] [less ▲]

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See detailAnalysis of historical grating spectra: Jungfraujoch atmospheric database extended back to 1977
Demoulin, Philippe ULg; Roland, Ginette; Bader, Whitney ULg et al

Conference (2011, November 10)

Historical solar spectra recorded at the Jungfraujoch station with a high-resolution grating spectrometer have been re-analyzed to derive total columns of a series of atmospheric gases. This instrument ... [more ▼]

Historical solar spectra recorded at the Jungfraujoch station with a high-resolution grating spectrometer have been re-analyzed to derive total columns of a series of atmospheric gases. This instrument, built and operated by the University of Liège (Belgium), was used in the Sixties and Seventies to record two solar spectrum atlases extending from the near-UV to the near-IR. From 1977 to 1989, it was also regularly used to record narrow spectral intervals in the mid-infrared, encompassing absorption lines of gases of atmospheric interest, e.g. CH4, HF, HCl, H2O, N2O, NO2, C2H6, O3 and CO. More than 10 thousand spectra were recorded during this period. The total columns derived from these grating spectra have been combined with the FTIR columns derived at the Jungfraujoch since the mid-1980s, in order to derive the temporal evolution of various target gases for the period 1977-2011. [less ▲]

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See detailChanges in atmospheric composition discerned from long-term NDACC measurements: trends in direct greenhouse gases derived from infrared solar absorption spectra recorded at the Jungfraujoch station
Mahieu, Emmanuel ULg; Duchatelet, Pierre ULg; Zander, Rodolphe ULg et al

Poster (2011, October 25)

The University of Liège (ULg) is operating -under clear sky conditions- two state-of-the-art Fourier Transform Infrared (FTIR) spectrometers at the high-altitude research station of the Jungfraujoch ... [more ▼]

The University of Liège (ULg) is operating -under clear sky conditions- two state-of-the-art Fourier Transform Infrared (FTIR) spectrometers at the high-altitude research station of the Jungfraujoch (Swiss Alps, 46.5ºN, 3580m asl), within the framework of the Network for the Detection of Atmospheric Composition Changes (NDACC). Routine FTIR operation started in 1984. Since then, it has been continued without disruption, allowing collecting more than 45000 high-resolution broadband IR solar absorption spectra, between 2 and 16 µm, using either HgCdTe or InSb detectors as well as a suite of optical filters. Typically, the spectral resolutions achieved lie in the 0.003 to 0.009 cm-1 interval while signal-to-noise ratios of 1000 and more are reached. Numerous narrow-band IR spectra essentially recorded from 1976 to 1989 with grating instruments are also available. Their analyses with modern tools have recently started [Bader et al., 2011] and will be pursued to consistently extend our datasets back in the 1970s. Geophysical parameters are deduced from the ULg observational database either with the SFIT-1, SFIT-2 or PROFFIT-9 algorithm, allowing producing total column time series of the target gases. In addition, information on their vertical distributions with altitude can generally be derived when using SFIT-2 or PROFFIT-9 which both implement the Optimal Estimation Method of Rodgers [1990]. Presently, more than two dozen atmospheric species are systematically retrieved from the Jungfraujoch observations, allowing the monitoring of key constituents of the Earth's atmosphere which play important roles in stratospheric ozone depletion and/or in global warming. This communication will focus on the direct and major greenhouse gases available from our database, namely water vapor, CO2, CH4, N2O, tropospheric ozone, CFC-11, CFC-12, HCFC-22, CCl4, SF6, as well as CF4 which has recently been added to our targets list [Duchatelet et al., 2011]. Trends and associated uncertainties characterizing the available -and often multi-decadal- time series have been derived or updated with a statistical bootstrap resampling tool [Gardiner et al., 2008], they will be presented and critically compared with data available from the literature. [less ▲]

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