References of "Servais, Christian"
     in
Bookmark and Share    
Full Text
See detailOzone tropospheric and stratospheric trends (1995-2012) at six ground-based FTIR stations (28°N to 79°N)
Vigouroux, Corinne; De Mazière, Martine; Demoulin, Philippe ULg et al

Poster (2013, April)

In the frame of the Network for the Detection of Atmospheric Composition Change (NDACC), contributing ground-based stations have joined their efforts to homogenize and optimize the retrievals of ozone ... [more ▼]

In the frame of the Network for the Detection of Atmospheric Composition Change (NDACC), contributing ground-based stations have joined their efforts to homogenize and optimize the retrievals of ozone profiles from FTIR (Fourier transform infrared) solar absorption spectra. Using the optimal estimation method, distinct vertical information can be obtained in four layers: ground-10 km, 10-18 km, 18-27 km, and 27-42 km, in addition to total column amounts. In a previous study, Vigouroux et al. (2008) applied a bootstrap resampling method to determine the trends of the ozone total and four partial columns, over the period 1995-2004 at Western European stations. The updated trends for the period 1995-2009 have been published in the WMO 2010 report. Here, we present the updated trends and their uncertainties, for the 1995-2012 period, for the different altitude ranges, above five European stations (28°N-79°N) and above the station Thule, Greenland (77°N). In this work, the trends have been estimated using a multiple regression model including some explanatory variables responsible for the ozone variability, such as the Quasi Biennial Oscillation (QBO), the solar flux, the Arctic Oscillation (AO) or El Niño-Southern Oscillation (ENSO). A major result is the significant positive trend of ozone in the upper stratosphere, observed at the Jungfraujoch (47°N), which is a typical mid-latitude site, as well as at the high latitude stations. This positive trend in the upper stratosphere at Jungfraujoch provides a sign of ozone recovery at mid-latitudes. [less ▲]

Detailed reference viewed: 28 (0 ULg)
Full Text
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 ▲]

Detailed reference viewed: 189 (25 ULg)
Full Text
Peer Reviewed
See detailValidation of IASI FORLI carbon monoxide retrievals using FTIR data from NDACC
Kerzenmacher, T; Dils, B; Kumps, N et al

in Atmospheric Measurement Techniques (2012), 5

Carbon monoxide (CO) is retrieved daily and globally from space-borne IASI radiance spectra using the Fast Optimal Retrievals on Layers for IASI (FORLI) software developed at the Université Libre de ... [more ▼]

Carbon monoxide (CO) is retrieved daily and globally from space-borne IASI radiance spectra using the Fast Optimal Retrievals on Layers for IASI (FORLI) software developed at the Université Libre de Bruxelles (ULB). The IASI CO total column product for 2008 from the most recent FORLI retrieval version (20100815) is evaluated using correlative CO profile products retrieved from groundbased solar absorption Fourier transform infrared (FTIR) observations at the following FTIR spectrometer sites from the Network for the Detection of Atmospheric Composition Change (NDACC): Ny-Alesund, Kiruna, Bremen, Jungfraujoch, Izana and Wollongong. In order to have good statistics for the comparisons, we included all IASI data from the same day, within a 100 km radius around the ground-based stations. The individual ground-based data were adjusted to the lowest altitude of the co-located IASI CO profiles. To account for the different vertical resolutions and sensitivities of the ground-based and satellite measurements, the averaging kernels associated with the various retrieved products have been used to properly smooth coincident data products. It has been found that the IASI CO total column products compare well on average with the co-located ground-based FTIR total columns at the selected NDACC sites and that there is no significant bias for the mean values at all stations. [less ▲]

Detailed reference viewed: 75 (0 ULg)
Full Text
Peer Reviewed
See detailAnalysis of stratospheric NO2 trends above Jungfraujoch using ground-based UV-visible, FTIR, and satellite nadir observations
Hendrick, F; Mahieu, Emmanuel ULg; Bodeker, G E et al

in Atmospheric Chemistry and Physics (2012), 12

The trend in stratospheric NO2 column at the NDACC (Network for the Detection of Atmospheric Composition Change) station of Jungfraujoch (46.5°N, 8.0°E) is assessed using ground-based FTIR and zenith ... [more ▼]

The trend in stratospheric NO2 column at the NDACC (Network for the Detection of Atmospheric Composition Change) station of Jungfraujoch (46.5°N, 8.0°E) is assessed using ground-based FTIR and zenith-scattered visible sunlight SAOZ measurements over the period 1990 to 2009 as well as a composite satellite nadir data set constructed from ERS-2/GOME, ENVISAT/SCIAMACHY, and METOP-A/GOME-2 observations over the 1996–2009 period. To calculate the trends, a linear least squares regression model including explanatory variables for a linear trend, the mean annual cycle, the quasi-biennial oscillation (QBO), solar activity, and stratospheric aerosol loading is used. For the 1990–2009 period, statistically indistinguishable trends of -3.7±1.1%/decade and -3.6±0.9%/decade are derived for the SAOZ and FTIR NO2 column time series, respectively. SAOZ, FTIR, and satellite nadir data sets show a similar decrease over the 1996–2009 period, with trends of -2.4±1.1%/decade, -4.3±1.4%/decade, and -3.6±2.2%/decade, respectively. The fact that these declines are opposite in sign to the globally observed +2.5%/decade trend in N2O, suggests that factors other than N2O are driving the evolution of stratospheric NO2 at northern mid-latitudes. Possible causes of the decrease in stratospheric NO2 columns have been investigated. The most likely cause is a change in the NO2/NO partitioning in favor of NO, due to a possible stratospheric cooling and a decrease in stratospheric chlorine content, the latter being further confirmed by the negative trend in the ClONO2 column derived from FTIR observations at Jungfraujoch. Decreasing ClO concentrations slows the NO+ ClO -> NO2 + Cl reaction and a stratospheric cooling slows the NO+O3 -> NO2 +O2 reaction, leaving more NOx in the form of NO. The slightly positive trends in ozone estimated from ground- and satellitebased data sets are also consistent with the decrease of NO2 through the NO2 +O3 -> NO3 +O2 reaction. Finally, we cannot rule out the possibility that a strengthening of the Dobson-Brewer circulation, which reduces the time available for N2O photolysis in the stratosphere, could also contribute to the observed decline in stratospheric NO2 above Jungfraujoch. [less ▲]

Detailed reference viewed: 131 (20 ULg)
Full Text
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 ▲]

Detailed reference viewed: 21 (4 ULg)
Full Text
See detailOzone tropospheric and stratospheric trends (1995-2011) at six ground-based FTIR stations (28°N to 79°N)
Vigouroux, Corinne; De Mazière, Martine; Demoulin, Philippe ULg et al

Poster (2012, August)

Five ground-based stations in Western Europe, from 79°N to 28°N, all part of the Network for the Detection of Atmospheric Composition Change (NDACC), have joined their efforts to homogenize and optimize ... [more ▼]

Five ground-based stations in Western Europe, from 79°N to 28°N, all part of the Network for the Detection of Atmospheric Composition Change (NDACC), have joined their efforts to homogenize and optimize the retrievals of ozone profiles from FTIR (Fourier transform infrared) solar absorption spectra. Using the optimal estimation method, distinct vertical information can be obtained in four layers: ground—10 km, 10—18 km, 18—27 km, and 27—42 km, in addition to total column amounts. Vigouroux et al. (2008) applied a bootstrap resampling method to the ozone data to determine the trends of the total columns and of the partial columns in the above four layers, over the period 1995-2004. The updated trends for the period 1995-2009 have been published in the WMO 2010 report. Here, we present the updated trends, obtained using the bootstrap resampling method, for the 1995-mid-2011 period, for the five European stations and also for the station Thule, Greenland (77°N), which has joined this effort. The trends have also been estimated using a multiple regression model including the Quasi Biennial Oscillation (QBO) and the solar flux as explanatory variables. The trends obtained by the two methods will be compared and discussed. One of the major results is the significant positive trend observed in the upper stratosphere at the station Jungfraujoch (47°N), which provides a sign of ozone recovery at mid-latitudes. Significant positive trends are also observed in the upper stratosphere at the high latitude stations. [less ▲]

Detailed reference viewed: 27 (0 ULg)
Full Text
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 ▲]

Detailed reference viewed: 176 (29 ULg)
Full Text
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 ▲]

Detailed reference viewed: 98 (13 ULg)
Full Text
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 ▲]

Detailed reference viewed: 145 (22 ULg)
Full Text
Peer Reviewed
See detailObserved and simulated time evolution of HCl, ClONO2, and HF total column abundances
Kohlhepp, R; Ruhnke, R; Chipperfield, M P et al

in Atmospheric Chemistry and Physics (2012), 12(7), 3527--3556

Time series of total column abundances of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) were determined from ground-based Fourier transform infrared (FTIR) spectra ... [more ▼]

Time series of total column abundances of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) were determined from ground-based Fourier transform infrared (FTIR) spectra recorded at 17 sites belonging to the Network for the Detection of Atmospheric Composition Change (NDACC) and located between 80.05°N and 77.82°S. By providing such a near-global overview on ground-based measurements of the two major stratospheric chlorine reservoir species, HCl and ClONO2, the present study is able to confirm the decrease of the atmospheric inorganic chlorine abundance during the last few years. This decrease is expected following the 1987 Montreal Protocol and its amendments and adjustments, where restrictions and a subsequent phase-out of the prominent anthropogenic chlorine source gases (solvents, chlorofluorocarbons) were agreed upon to enable a stabilisation and recovery of the stratospheric ozone layer. The atmospheric fluorine content is expected to be influenced by the Montreal Protocol, too, because most of the banned anthropogenic gases also represent important fluorine sources. But many of the substitutes to the banned gases also contain fluorine so that the HF total column abundance is expected to have continued to increase during the last few years. The measurements are compared with calculations from five different models: the two-dimensional Bremen model, the two chemistry-transport models KASIMA and SLIMCAT, and the two chemistry-climate models EMAC and SOCOL. Thereby, the ability of the models to reproduce the absolute total column amounts, the seasonal cycles, and the temporal evolution found in the FTIR measurements is investigated and inter-compared. This is especially interesting because the models have different architectures. The overall agreement between the measurements and models for the total column abundances and the seasonal cycles is good. Linear trends of HCl, ClONO2, and HF are calculated from both measurement and model time series data, with a focus on the time range 2000–2009. This period is chosen because from most of the measurement sites taking part in this study, data are available during these years. The precision of the trends is estimated with the bootstrap resampling method. The sensitivity of the trend results with respect to the fitting function, the time of year chosen and time series length is investigated, as well as a bias due to the irregular sampling of the measurements. The measurements and model results investigated here agree qualitatively on a decrease of the chlorine species by around 1%yr-1. The models simulate an increase of HF of around 1%yr-1. This also agrees well with most of the measurements, but some of the FTIR series in the Northern Hemisphere show a stabilisation or even a decrease in the last few years. In general, for all three gases, the measured trends vary more strongly with latitude and hemisphere than the modelled trends. Relative to the FTIR measurements, the models tend to underestimate the decreasing chlorine trends and to overestimate the fluorine increase in the Northern Hemisphere. At most sites, the models simulate a stronger decrease of ClONO2 than of HCl. In the FTIR measurements, this difference between the trends of HCl and ClONO2 depends strongly on latitude, especially in the Northern Hemisphere. [less ▲]

Detailed reference viewed: 139 (14 ULg)
Full Text
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 ▲]

Detailed reference viewed: 170 (35 ULg)
Full Text
Peer Reviewed
See detailDecrease of the Carbon Tetrachloride (CCl4) Loading above Jungfraujoch, based on High Resolution Infrared Solar Spectra recorded between 1999 and 2011
Rinsland, C. P.; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2012), 113

The long-term trend of the atmospheric carbon tetrachloride (CCl4) burden has been retrieved from high spectral resolution infrared solar absorption spectra recorded between January 1999 and June 2011 ... [more ▼]

The long-term trend of the atmospheric carbon tetrachloride (CCl4) burden has been retrieved from high spectral resolution infrared solar absorption spectra recorded between January 1999 and June 2011. The observations were made with a Fourier transform spectrometer at the northern mid-latitude, high altitude Jungfraujoch station in Switzerland (46.5°N latitude, 8.0°E longitude, 3580 m altitude). Total columns were derived from spectrometric analysis of the strong CCl4 ν3 band at 794 cm-1, accounting for all interfering molecules (e.g., H2O, CO2, O3, and a dozen weakly absorbing gases). A significant improvement in the fitting residuals and in the retrieved CCl4 columns was obtained by taking into account line mixing in a strong interfering CO2 Q branch. This procedure had never been implemented in remote sensing CCl4 retrievals though its importance was noted in earlier studies. A fit to the CCl4 daily mean total column time series returns a statistically-significant long-term trend of (-1.49±0.08 x 1013 molec./cm2)/yr, 2-σ. This corresponds to an annual decrease of (-1.31±0.07) pptv for the mean free tropospheric volume mixing ratio. Furthermore, the total column data set reveals a weak seasonal cycle with a peak-to-peak amplitude of 4.5 %, with minimum and maximum values occurring in mid-February and mid-September, respectively. This small seasonal modulation is attributed primarily to the residual influence of tropopause height changes throughout the year. The negative trend of the CCl4 loading reflects the continued impact of the regulations implemented by the Montreal Protocol and its strengthening amendments and adjustments. Despite this statistically significant decrease, the CCl4 molecule currently remains an important contributor to the atmospheric chlorine budget, and thus deserves further monitoring, to ensure continued compliance with these strengthenings, globally. Our present findings are briefly discussed with respect to recent relevant CCl4 investigations at the ground and from space. [less ▲]

Detailed reference viewed: 87 (10 ULg)
Full Text
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 ▲]

Detailed reference viewed: 250 (31 ULg)
Full Text
See detailLong-term series of tropospheric water vapour amounts and HDO/H2O ratio profiles above Jungfraujoch
Lejeune, Bernard ULg; Mahieu, Emmanuel ULg; Schneider, Matthias et al

in Geophysical Research Abstracts (2012), 14

Water vapour is a crucial climate variable involved in many processes which widely determine the energy budget of our planet. In particular, water vapour is the dominant greenhouse gas in the Earth’s ... [more ▼]

Water vapour is a crucial climate variable involved in many processes which widely determine the energy budget of our planet. In particular, water vapour is the dominant greenhouse gas in the Earth’s atmosphere and its radiative forcing is maximum in the middle and upper troposphere. Because of the extremely high variability of water vapour concentration in time and space, it is challenging for the available relevant measurement techniques to provide a consistent data set useful for trend analyses and climate studies. Schneider et al. (2006a) showed that ground-based Fourier Transform Infrared (FTIR) spectroscopy, performed from mountain observatories, allows for the detection of H2O variabilities up to the tropopause. Furthermore, the FTIR measurements allow the retrieval of HDO amounts and therefore the monitoring of HDO/H2O ratio profiles whose variations act as markers for the source and history of the atmospheric water vapour. In the framework of the MUSICA European project (Multi-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water, http://www.imk-asf.kit.edu/english/musica.php), a new approach has been developed and optimized by M. Schneider and F. Hase, using the PROFFIT algorithm, to consistently retrieve tropospheric water vapour profiles from high-resolution ground-based infrared solar spectra and so taking benefit from available long-term data sets of ground-based observations. The retrieval of the water isotopologues is performed on a logarithmic scale from 14 micro-windows located in the 2600-3100 cm-1 region. Other important features of this new retrieval strategy are: a speed dependant Voigt line shape model, a joint temperature profile retrieval and an interspecies constraint for the HDO/H2O profiles. In this contribution, we will combine the quality of the MUSICA strategy and of our observations, which are recorded on a regular basis with FTIR spectrometers, under clear-sky conditions, at the NDACC site (Network for the Detection of Atmospheric Composition Change, http://www.ndacc.org) of the Jungfraujoch International Scientific Station (Swiss Alps, 46.5°N, 8.0°E, 3580m asl). Information content analysis of the retrieved H2O products allows us to produce a long-term trend from 1996 to 2011 for different tropospheric levels. We will compare the annual cycle of tropospheric HDO/H2O ratio profiles with those already produced at other sites (Schneider et al., 2010). We will also focus on the diurnal variability of water vapour to determine a time limit in the inter-comparison of different water vapour measurement techniques. [less ▲]

Detailed reference viewed: 204 (20 ULg)
Full Text
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 ▲]

Detailed reference viewed: 482 (36 ULg)
Full Text
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 ▲]

Detailed reference viewed: 14 (4 ULg)
Full Text
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 ▲]

Detailed reference viewed: 196 (25 ULg)
Full Text
Peer Reviewed
See detailCarbon monoxide (CO) and ethane (C2H6) trends from ground-based solar FTIR measurements at six European stations, comparison and sensitivity analysis with the EMEP model
Angelbratt, J.; Mellqvist, J.; Simpson, D. et al

in Atmospheric Chemistry and Physics (2011), 11(17), 9253--9269

Trends in the CO and C2H6 partial columns ~0–15 km) have been estimated from four European ground-based solar FTIR (Fourier Transform InfraRed) stations for the 1996–2006 time period. The CO trends from ... [more ▼]

Trends in the CO and C2H6 partial columns ~0–15 km) have been estimated from four European ground-based solar FTIR (Fourier Transform InfraRed) stations for the 1996–2006 time period. The CO trends from the four stations Jungfraujoch, Zugspitze, Harestua and Kiruna have been estimated to −0.45 ± 0.16% yr−1, −1.00 ± 0.24% yr−1, −0.62 ± 0.19 % yr−1 and −0.61 ± 0.16% yr−1, respectively. The corresponding trends for C2H6 are −1.51 ± 0.23% yr−1, −2.11 ± 0.30% yr−1, −1.09 ± 0.25% yr−1 and −1.14 ± 0.18% yr−1. All trends are presented with their 2-σ confidence intervals. To find possible reasons for the CO trends, the global-scale EMEP MSC-W chemical transport model has been used in a series of sensitivity scenarios. It is shown that the trends are consistent with the combination of a 20% decrease in the anthropogenic CO emissions seen in Europe and North America during the 1996–2006 period and a 20% increase in the anthropogenic CO emissions in East Asia, during the same time period. The possible impacts of CH4 and biogenic volatile organic compounds (BVOCs) are also considered. The European and global-scale EMEP models have been evaluated against the measured CO and C2H6 partial columns from Jungfraujoch, Zugspitze, Bremen, Harestua, Kiruna and Ny-Ålesund. The European model reproduces, on average the measurements at the different sites fairly well and within 10–22% deviation for CO and 14–31% deviation for C2H6. Their seasonal amplitude is captured within 6–35% and 9–124% for CO and C2H6, respectively. However, 61–98% of the CO and C2H6 partial columns in the European model are shown to arise from the boundary conditions, making the global-scale model a more suitable alternative when modeling these two species. In the evaluation of the global model the average partial columns for 2006 are shown to be within 1–9% and 37–50% of the measurements for CO and C2H6, respectively. The global model sensitivity for assumptions made in this paper is also analyzed. [less ▲]

Detailed reference viewed: 44 (4 ULg)