Evolution of methanol (CH3OH) above the Jungfraujoch station (46.5°N) : Variability, seasonal modulation and long-term trend.

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 ▲]

First retrievals of methanol (CH3OH) above Jungfraujoch (46.5°N) : Optimization of retrieval strategy and information content.

Poster (2012, December 10)

Validation of IASI FORLI carbon monoxide retrievals using FTIR data from NDACC

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 ▲]

Long-term trends of NO above northern mid-latitudes as inferred from Jungfraujoch, HALOE and ACE-FTS solar observations

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 ▲]

Retrievals of ethane from ground-based high-resolution FTIR solar observations with updated line parameters: determination of the optimum strategy for the Jungfraujoch station.

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 ▲]

Retrieval of methanol (CH3OH) above the high-altitude Jungfraujoch station (46.5ºN): preliminary total column time series, long-term trend and seasonal modulation

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 ▲]

Observed and simulated time evolution of HCl, ClONO2, and HF total column abundances

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 ▲]

Fourier Transform Infrared Spectrometry

in Kämpfer, Niklaus (Ed.) Monitoring Atmospheric Water Vapour : Ground-Based Remote Sensing and In-situ Methods (2012)

Retrievals of ethane from ground-based high-resolution FTIR solar observations with updated line parameters: determination of the optimum strategy for the Jungfraujoch station.

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 ▲]

Analysis of historical grating spectra: Jungfraujoch atmospheric database extended back to 1977

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 ▲]