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See detailTrend evolution and seasonal variation of tropospheric and stratospheric carbonyl sulfide (OCS) above Jungfraujoch
Lejeune, Bernard ULg; Mahieu, Emmanuel ULg; Duchatelet, Pierre ULg et al

in Geophysical Research Abstracts (2011), 13

Carbonyl sulfide (OCS) is the most abundant sulfur-containing trace gas in the atmosphere and accounts for a substantial portion of the sulfur in the stratospheric aerosol layer which influences the ... [more ▼]

Carbonyl sulfide (OCS) is the most abundant sulfur-containing trace gas in the atmosphere and accounts for a substantial portion of the sulfur in the stratospheric aerosol layer which influences the Earth’s radiation budget and stratospheric ozone chemistry. The major identified OCS sources are oceans and anthropogenic emissions, while atmospheric loss and uptake by vegetation and soils constitute the main OCS sinks. The uptake by vegetation strongly influences the distribution and seasonality of OCS throughout most of the Northern Hemisphere, just like for CO2. Montzka et al. (2007) pointed that atmospheric OCS measurements have the potential to constrain the biomass Gross Primary Production (GPP). Unfortunately, there remain large uncertainties on some components strengths of the atmospheric OCS budget. A recent work by Suntharalingam et al. (2008) showed that uptake by plants has been strongly underestimated in actual balanced budgets, suggesting that additional significant OCS sources have still to be identified. In order to improve our understanding of the different processes governing seasonal and inter-annual OCS variability, a new approach has been developed and optimized, using the SFIT-2 algorithm, to retrieve atmospheric abundance of OCS from high-resolution ground-based infrared solar spectra. Our observations are recorded on a regular basis with Fourier Transform Infrared spectrometers (FTIRs), under clear-sky conditions, at the NDACC site (Network for the Detection of Atmospheric Composition Change, http://www.ndacc.org) of the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580m asl). Information content analysis of the retrieved OCS products shows us that we are able to distinguish between tropospheric and stratospheric partial column contributions for this species. Thanks to our unique observational database, we have produced an updated OCS long-term trend from 1995 to 2010, representative for both the troposphere and stratosphere at northern mid-latitudes. In this contribution, we will present and critically discuss the recent OCS trend evolution, in particular the end of the slow decline of its abundance observed in 2002 and the maximum reached in 2008. In addition to the OCS inter-annual variations, we will analyze the OCS seasonal cycle during the 15 last years. We will also compare our results with simulations of seasonal OCS variations issued from a 3D global atmospheric chemical transport model (CTM), in order to try to quantify the individual contribution of the various processes playing a role in the Jungfraujoch OCS variability and influencing its atmospheric abundance. [less ▲]

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See detailFirst retrievals of carbon tetrafluoride (CF4) from ground-based FTIR measurements: production and analysis of the two-decadal time series above the Jungfraujoch
Duchatelet, Pierre ULg; Zander, Rodolphe ULg; Mahieu, Emmanuel ULg et al

in Geophysical Research Abstracts (2011)

Carbon tetrafluoride (CF4 or PFC-14) is a potent greenhouse gas that is almost 7400 times more effective (100-yr horizon) than CO2 on a per molecule basis (IPCC, 2007). This high global warming potential ... [more ▼]

Carbon tetrafluoride (CF4 or PFC-14) is a potent greenhouse gas that is almost 7400 times more effective (100-yr horizon) than CO2 on a per molecule basis (IPCC, 2007). This high global warming potential, coming from its medium absorbance combined with a very long atmospheric lifetime (>50000 years; Ravishankara et al., 1993), makes CF4 a key species among the various greenhouse gases targeted by the Kyoto Protocol. In the Northern hemisphere, current atmospheric CF4 concentrations are close to 78 pptv, with a large fraction (around 35 pptv, Mühle et al., 2010) coming from natural processes like lithospheric emissions (Harnisch and Eisenhauer, 1998). In addition, CF4 has been used increasingly since the eighties in electronic and semiconductors industry. The primary aluminum production processes have also been clearly identified as an important anthropogenic source of CF4 emissions. The partitioning between these two main sources is however problematic, principally due to lacking or incomplete CF4 emission factors from inventories performed in industrial fields (e.g. International Aluminum Institute, 2009). Recent in situ ground level measurements of CF4 in the Northern hemisphere (Khalil et al., 2003; Mühle et al., 2010) or remotely from space (Rinsland et al., 2006) have indicated a significant slowdown in the increase rate of atmospheric CF4. This probably results from measures adopted by the aluminum industry aiming at the reduction of the frequency and duration of “anode effects” and therefore of related PFCs emissions (International Aluminum Institute, 2009). The present contribution reports on the long-term evolution (1990-2010) of the atmospheric carbon tetrafluoride total vertical abundance derived from ground-based Fourier transform infrared (FTIR) solar spectroscopy observations around 1285 cm-1 at the Jungfraujoch (46.5°N, 8.0°E, 3580m asl) and compares our findings with results available in the literature. To our knowledge, no equivalent time series (i.e. based on ground-based FTIR technique) has been published to date. [less ▲]

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See detailFirst retrievals of methyl chloride from ground-based high-resolution FTIR solar observations
Mahieu, Emmanuel ULg; Harrison, Jeremy; Bernath, Peter F. et al

in Geophysical Research Abstracts (2011), 13

Methyl chloride (CH3Cl) is one of the most abundant chlorine-bearing gas in the Earth’s troposphere and a significant contributor to the organic chlorine budget. Measurements by in situ networks indicate ... [more ▼]

Methyl chloride (CH3Cl) is one of the most abundant chlorine-bearing gas in the Earth’s troposphere and a significant contributor to the organic chlorine budget. Measurements by in situ networks indicate a mean volume mixing ratio of 550 pptv, with a significant seasonal cycle of about 80 pptv, peak to peak. This species also exhibits inter-annual variability, but no long-term trend. Major sources are from tropical and sub-tropical plants and dead leaves, the oceans and biomass burning. Some industrial processes and waste incineration further add to the emissions. Oxidation by the hydroxyl radical is by far the largest CH3Cl sink, followed by soil uptake. Although balanced, its atmospheric budget is still affected by large uncertainties and contributions from unidentified sources and sinks cannot be ruled out. Methyl chloride has an atmospheric lifetime of 1 year, a global warming potential of 13 (100-yr horizon) and an ozone depleting potential of 0.02. The retrieval of methyl chloride from ground-based infrared (IR) spectra is very challenging. Indeed, numerous interferences by strong water vapor and methane lines complicate the detection of small CH3Cl absorptions, close to 1%, near 3 microns. In addition, and although weak, ethane features contribute to the difficulty, in particular since a significant number of ethane branches were absent until very recently from official HITRAN compilations. Therefore, the scientific literature does not report thus far about any investigations of CH3Cl from ground-based remote sensing observations. In this contribution, we will present first CH3Cl total column retrievals, using the SFIT-2 algorithm (v3.94) and high-resolution Fourier Transform Infrared (FTIR) solar absorption observations recorded with a 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). In our retrievals, we use new ethane absorption cross sections recorded at the Molecular Spectroscopy Facility of the Rutherford Appleton Laboratory (Harrison et al., 2010). They were calibrated in intensity by using reference low-resolution spectra from the Pacific Northwest National Laboratory (PNNL) IR database. These new cross sections were recently released as a HITRAN update (see http://www.hitran.com). 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, including our target CH3Cl. We will evaluate the improvement brought by the new ethane line parameters on the fitting residuals, and characterize the quality, the precision and the reliability of the retrieved product. If successful, a long-term CH3Cl total column time series will be produced using the Jungfraujoch observational database, and we will perform preliminary investigations of the seasonal and inter-annual variations of methyl chloride total columns at northern mid-latitudes. [less ▲]

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See detailThe evolution of the inorganic fluorine budget since the mid-1980s based on FTIR measurements at northern mid-latitudes
Duchatelet, Pierre ULg; Feng, Wuhu; Chipperfield, Martyn et al

in Geophysical Research Abstracts (2011)

Fluorine enters the stratosphere principally in the form of CFCs (chlorofluorocarbons, mainly CFC-12 and CFC-11), HCFCs (hydrochlorofluorocarbons, mainly HCFC-22) and HFCs (hydrofluorocarbons, mainly HFC ... [more ▼]

Fluorine enters the stratosphere principally in the form of CFCs (chlorofluorocarbons, mainly CFC-12 and CFC-11), HCFCs (hydrochlorofluorocarbons, mainly HCFC-22) and HFCs (hydrofluorocarbons, mainly HFC-134a) which have been (or are still) widely emitted at ground level by human activities. In the lower stratosphere, the photolysis of these halogenated source gases leads to the formation of the two fluorine reservoirs COClF and COF2. The subsequent photolysis of these two compounds frees F atoms, which principally react with CH4 and H2O to form the extremely stable HF gas, by far the dominant fluorine reservoir in the middle and upper stratosphere. Despite the fact that fluorine does not significantly contribute in stratospheric ozone depletion, measurements of the concentrations of individual F-containing species in different altitude ranges of the atmosphere are important as they reflect the amounts of anthropogenic gases transported into the middle atmosphere as well as their decomposition. Such measurements also provide insight into the partitioning between major fluorine source gases (which are potent greenhouse gases) and reservoirs and allows a global inventory of organic (CFy), inorganic (Fy) and total (FTOT) fluorine burdens to be monitored as a function of time. Indeed, regular updates of such inventories are important as the partitioning between F-containing gases in the stratosphere is continually evolving as emissions of anthropogenic gases from the surface change, principally as a consequence of the progressive ban on the production of CFCs and HCFCs adopted by the Montreal Protocol and its subsequent Amendments and Adjustments. To complement recent studies regarding fluorine species (Duchatelet et al., 2009, 2010, 2011; Mahieu et al., 2011), this communication presents the time series of the inorganic fluorine budget Fy over the last twenty-five years, based on HF and COF2 total column amounts derived from high resolution Fourier transform infrared (FTIR) solar spectra recorded at Jungfraujoch (46.5°N, 8.0°E, 3580m asl). A trend analysis of our HF, COF2 and Fy time series is performed and discussed in the context of past and current emissions of halogenated source gases. Comparisons with model and space data are also included. [less ▲]

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See detailTrend and lifetime of sulfur hexafluoride at mid-latitudes deduced from ACE-FTS occultation measurements
Mahieu, Emmanuel ULg; Duchatelet, Pierre ULg; Zander, Rodolphe ULg et al

in Geophysical Research Abstracts (2011), 13

Sulfur hexafluoride (SF6) is one of the strongest greenhouse gases on a per molecule basis, with a global warming potential of 22800 (100-yr horizon). This is an extremely stable gas in the atmosphere ... [more ▼]

Sulfur hexafluoride (SF6) is one of the strongest greenhouse gases on a per molecule basis, with a global warming potential of 22800 (100-yr horizon). This is an extremely stable gas in the atmosphere, which results in a very long lifetime, with large uncertainties. The value adopted by IPCC is 3200 years, but some studies suggest shorter lifetimes, as low as 800 years. Surface concentrations are now about 7 ppt, with reported trends indicating a steady and strong increase of 0.3 ppt/yr. Most emissions are of anthropogenic origin, related to its use as an insulator in high-voltage electrical installations. Secondary contributions result from magnesium and aluminum production as well as from the manufacturing of semiconductors (see e.g. Levin et al., 2010; Rigby et al., 2010 and references therein). In this contribution, we use occultation measurements performed by the ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer) instrument, launched in August 2003 onboard the Canadian SCISAT satellite (Bernath et al., 2005). ACE-FTS is still in operation to date, with no significant degradation in its performance. This spectrometer achieves a spectral resolution of 0.02 cm-1 in the broad 750-4400 cm-1 range which covers the unresolved nu-3 band Q branch of SF6 centered at 947.9 cm-1. Signal-to-noise ratios of 200-300 are typically obtained in the spectral region of interest. Version 3 retrievals performed by University of Waterloo give volume mixing ratio profiles of SF6 in the 11-32 km altitude range. We consider all available sunrise and sunset occultation measurements obtained at midlatitudes in both hemispheres to derive the trend of SF6 in the lower stratosphere, from late February 2004 onwards. Consistency between both hemispheres will be investigated. In addition, concurrent N2O measurements are used to evaluate the atmospheric lifetime of SF6, following a method used previously for other long-lived gases (e.g. Zander et al, 1996). Comparisons with trends derived from in situ surface measurements or from ground-based remote-sensing observations (e.g. at the Jungfraujoch station, 46.5ºN) are also included. [less ▲]

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See detailOzone-Depleting Substances (ODSs) and Related Chemicals (Chapter 1)
Montzka, S. A.; Reimann, S.; Engel, A. et al

in Nohende Ajavon, Ayité-Lô; Newmann, Paul A.; Pyle, John A. (Eds.) et al Scientific Assessment of Ozone Depletion: 2010 (2011)

The amended and adjusted Montreal Protocol continues to be successful at reducing emissions and atmospheric abundances of most controlled ozone-depleting substances (ODSs).

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See detailFormic acid above the Jungfraujoch during 1985–2007: observed variability, seasonality, but no long-term background evolution
Zander, Rodolphe ULg; Duchatelet, Pierre ULg; Mahieu, Emmanuel ULg et al

in Atmospheric Chemistry and Physics (2010), 10(20), 10047--10065

This paper reports on daytime total vertical column abundances of formic acid (HCOOH) above the Northern mid-latitude, high altitude Jungfraujoch station (Switzerland; 46.5° N, 8.0° E, 3580 m alt.). The ... [more ▼]

This paper reports on daytime total vertical column abundances of formic acid (HCOOH) above the Northern mid-latitude, high altitude Jungfraujoch station (Switzerland; 46.5° N, 8.0° E, 3580 m alt.). The columns were derived from the analysis of infrared solar observations regularly performed with high spectral resolution Fourier transform spectrometers during over 1500 days between September 1985 and September 2007. The investigation was based on the spectrometric fitting of five spectral intervals, one encompassing the HCOOH ν6 band Q branch at 1105 cm−1, and four additional ones allowing to optimally account for critical temperature-sensitive or time-evolving interferences by other atmospheric gases, in particular HDO, CCl2F2 and CHClF2. The main results derived from the 22 years long database indicate that the free tropospheric burden of HCOOH above the Jungfraujoch undergoes important short-term daytime variability, diurnal and seasonal modulations, inter-annual anomalies, but no significant long-term background change. A major progress in the remote determination of the atmospheric HCOOH columns reported here has resulted from the adoption of new, improved absolute spectral line intensities for the infrared ν6 band of trans-formic acid, resulting in retrieved free tropospheric loadings being about a factor two smaller than if derived with previous spectroscopic parameters. Implications of this significant change with regard to earlier remote measurements of atmospheric formic acid and comparison with relevant Northern mid-latitude findings, both in situ and remote, will be assessed critically. Sparse HCOOH model predictions will also be evoked and assessed with respect to findings reported here. [less ▲]

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See detailUpdating hydrogen fluoride (HF) FTIR time series above Jungfraujoch: comparison of two retrieval algorithms and impact of line shape models
Duchatelet, Pierre ULg; Demoulin, Philippe ULg; Hase, Frank et al

Poster (2010, May)

Fluorine enters the stratosphere mainly in the form of chlorofluorocarbons (CFCs; principally CFC-11 and CFC-12) and tetrafluoromethane (CF4), which have been widely emitted at ground level by human ... [more ▼]

Fluorine enters the stratosphere mainly in the form of chlorofluorocarbons (CFCs; principally CFC-11 and CFC-12) and tetrafluoromethane (CF4), which have been widely emitted at ground level by human activities over the past few decades. In the lower stratosphere, the photolysis of the long-lived CFC-11 (CCl3F) and CFC-12 (CCl2F2), whose emissions from the ground have been progressively phased out by the Montreal Protocol and its successive Amendments and Adjustments, leads to the formation of the two reservoirs: COClF and COF2. Subsequent photolysis of these two compounds then liberates F atoms, which could quickly react with CH4, H2O or H2 to form the extreme stable hydrogen fluoride (HF) gas. The formation of HF by these reactions is significant, as they make HF the largest fluorine reservoir in the middle and upper stratosphere. Despite the fact that fluorine does not directly participate in ozone depletion, measurements of the concentration of individual F-containing species at different altitude of the atmosphere are important as they reflect the amounts of anthropogenic gases – which also often bear ozone-threatening Cl atoms - transported into the middle atmosphere as well as their decomposition. Since the first detection of hydrogen fluoride in the Earth’s atmosphere by Zander (1975), several studies dealing with HF total column amounts derived from ground-based Fourier transform infrared (FTIR) observations at several latitudes in both hemispheres have been published. In addition, these last years have seen the emergence of more sophisticated retrieval algorithms (e.g. SFIT-2, PROFFIT) allowing to inverse total or partial columns as well as vertical distribution of the target gas from ground-based FTIR spectra. In this contribution, we propose to compare HF total columns derived from FTIR high-resolution ground-based observations performed at the Jungfraujoch (46.5°N, 8.0°E, 3580 m asl) by using two different retrieval codes: SFIT-2 v.3.91 and PROFFIT v.9.5. The impact of spectroscopic parameters (Voigt line shape model versus Galatry model line shape) on HF retrievals is also analyzed. References: Zander, R.: Présence de HF dans la stratosphère supérieure, C.R. Acad. Sci. Paris. Série B., 281, 213-214, 1975. [less ▲]

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See detailValidation of five years (2003–2007) of SCIAMACHY CO total column measurements using ground-based spectrometer observations
de Laat, A. T. J.; Gloudemans, A. M. S.; Schrijver, H. et al

in Atmospheric Measurement Techniques (2010), 3(5), 1457--1471

This paper presents a validation study of SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) carbon monoxide (CO) total column measurements from the Iterative Maximum ... [more ▼]

This paper presents a validation study of SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) carbon monoxide (CO) total column measurements from the Iterative Maximum Likelihood Method (IMLM) algorithm using ground-based spectrometer observations from twenty surface stations for the five year time period of 2003–2007. Overall we find a good agreement between SCIAMACHY and ground-based observations for both mean values as well as seasonal variations. For high-latitude Northern Hemisphere stations absolute differences between SCIAMACHY and ground-based measurements are close to or fall within the SCIAMACHY CO 2σ precision of 0.2 × 1018 molecules/cm2 (~10%) indicating that SCIAMACHY can observe CO accurately at high Northern Hemisphere latitudes. For Northern Hemisphere mid-latitude stations the validation is complicated due to the vicinity of emission sources for almost all stations, leading to higher ground-based measurements compared to SCIAMACHY CO within its typical sampling area of 8° × 8°. Comparisons with Northern Hemisphere mountain stations are hampered by elevation effects. After accounting for these effects, the validation provides satisfactory results. At Southern Hemisphere mid- to high latitudes SCIAMACHY is systematically lower than the ground-based measurements for 2003 and 2004, but for 2005 and later years the differences between SCIAMACHY and ground-based measurements fall within the SCIAMACHY precision. The 2003–2004 bias is consistent with previously reported results although its origin remains under investigation. No other systematic spatial or temporal biases could be identified based on the validation presented in this paper. Validation results are robust with regard to the choices of the instrument-noise error filter, sampling area, and time averaging required for the validation of SCIAMACHY CO total column measurements. Finally, our results show that the spatial coverage of the ground-based measurements available for the validation of the 2003–2007 SCIAMACHY CO columns is sub-optimal for validation purposes, and that the recent and ongoing expansion of the ground-based network by carefully selecting new locations may be very beneficial for SCIAMACHY CO and other satellite trace gas measurements validation efforts. [less ▲]

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See detailLong-term trend of carbon tetrachloride (CCl4) from ground-based high resolution infrared solar spectra recorded at the Jungfraujoch
Rinsland, Curtis P.; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

in Geophysical Research Abstracts (2010), 12(EGU2010-1819-3),

The long-term trend of carbon tetrachloride (CCl4) has been retrieved from infrared high resolution solar absorption spectra encompassing the 1999 to 2010 time period. The measurements were recorded with ... [more ▼]

The long-term trend of carbon tetrachloride (CCl4) has been retrieved from infrared high resolution solar absorption spectra encompassing the 1999 to 2010 time period. The measurements were recorded 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 the region of the strong CCl4 _3 band at 794 cm􀀀1 accounting for all interfering molecules (e.g. H2O, O3) with significant improvement in the residuals obtained by also taking into account the line mixing in a nearby CO2 Q branch, a procedure not implemented in previous remote sensing CCl4 retrievals though its importance has been noted in several papers. The time series shows a statistically-significant long-term decrease in the CCl4 total atmospheric burden of -1.18_0.10 %/yr, at the 95% confidence level, using 2005 as reference. Furthermore, fit to the total column data set also reveals a seasonal cycle with a peak-to-peak amplitude of 10.2%, with minimum and maximum values found in mid-February and early August, respectively. This seasonal modulation can however be attributed to tropopause height changes throughout the season. The results quantify the continued impact of the regulations implemented by the Montreal Protocol and its strengthening amendments and adjustments for a molecule with high global warming potential. Although a statistically significant decrease in the total column is inferred, the CCl4 molecule remains an important contributor to the stratospheric chlorine budget and burden. [less ▲]

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See detailRecent trends of inorganic chlorine and halogenated source gases above the Jungfraujoch and Kitt Peak stations derived from high-resolution FTIR solar observations
Mahieu, Emmanuel ULg; Rinsland, Curtis P.; Gardiner, Tom et al

in Geophysical Research Abstracts (2010), 12(EGU2010-2420-3),

The longest series of Fourier Transform Infrared (FTIR) high spectral resolution solar absorption observations are available from the Jungfraujoch and Kitt Peak stations, located at 46.5ºN and 30.9ºN ... [more ▼]

The longest series of Fourier Transform Infrared (FTIR) high spectral resolution solar absorption observations are available from the Jungfraujoch and Kitt Peak stations, located at 46.5ºN and 30.9ºN, respectively. State-of-the-art interferometers are operated at these sites within the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). These instruments allow to record spectra on a regular basis, under clear-sky conditions, using a suite of optical filters which altogether cover the 2 to 16 micron spectral range. Numerous absorption features characterized in the HITRAN compilations (e.g. Rothman et al., 2008) are encompassed in this mid-infrared region. Their analyses with either the SFIT-1 or SFIT-2 algorithm allow retrieving total columns of the target gases. Moreover, information on their distribution with altitude can generally be derived when using SFIT-2 which implements the Optimal Estimation Method of Rodgers (1990). Among the two dozen gases of atmospheric interest accessible to the ground-based FTIR technique, we have selected here a suite of long-lived halogenated species: HCl, ClONO2, CCl2F2, CCl3F, CHClF2, CCl4 and SF6. Time series available from the two sites will be presented, compared and critically discussed. In particular, changes in the abundances of theses gases since the peak in inorganic chlorine (Cly, which occurred in 1996-1997) and their intra-annual variability will be characterized with a statistical tool using bootstrap resampling (Gardiner et al., 2008). Trends and their associated uncertainties will be reported and put into perspective with the phase-out regulations of the production of ozone depleting substances adopted and implemented by the Montreal Protocol, its Amendments and Adjustments. For instance, the trends affecting the reservoir species HCl, ClONO2, and their summation which is a good proxy of the total inorganic chlorine, have been calculated using all available daily mean measurements from January 1996 onwards. The following values were obtained for Jungfraujoch, when using 1996 as the reference year: -0.90±0.10%/yr for HCl, -0.92±0.26 %/yr for ClONO2, and -0.96±0.14 %/yr for Cly; in all cases, the uncertainties define the 95% confidence interval around the trend values. For Kitt Peak, the corresponding trends are: -0.55±0.34 %/yr for HCl, -1.27±0.84 %/yr for ClONO2 and -0.61±0.51 %/yr for Cly, they are statistically consistent with the Jungfraujoch rates of decrease. Further trend data will be presented at the EGU General Assembly while supplementary information on Jungfraujoch results will be available from communications at the same meeting by Duchatelet et al. (2010), Lejeune et al (2010) and Rinsland et al (2010). Comparisons with model data are also foreseen. [less ▲]

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See detailOptimized approach to retrieve information on the tropospheric and stratospheric carbonyl sulfide (OCS) vertical distributions above Jungfraujoch from high-resolution FTIR solar spectra
Lejeune, Bernard ULg; Mahieu, Emmanuel ULg; Servais, Christian ULg et al

in Geophysical Research Abstracts (2010), 12(EGU2010-3513),

Carbonyl sulfide (OCS), which is produced in the troposphere from both biogenic and anthropogenic sources, is the most abundant gaseous sulfur species in the unpolluted atmosphere. Due to its low chemical ... [more ▼]

Carbonyl sulfide (OCS), which is produced in the troposphere from both biogenic and anthropogenic sources, is the most abundant gaseous sulfur species in the unpolluted atmosphere. Due to its low chemical reactivity and water solubility, a significant fraction of OCS is able to reach the stratosphere where it is converted to SO2 and ultimately to H2SO4 aerosols (Junge layer). These aerosols have the potential to amplify stratospheric ozone destruction on a global scale and may influence Earth’s radiation budget and climate through increasing solar scattering. The transport of OCS from troposphere to stratosphere is thought to be the primary mechanism by which the Junge layer is sustained during nonvolcanic periods. Because of this, long-term trends in atmospheric OCS concentration, not only in the troposphere but also in the stratosphere, are of great interest. A new approach has been developed and optimized to retrieve atmospheric abundance of OCS from high-resolution ground-based infrared solar spectra by using the SFIT-2 (v3.91) algorithm, including a new model for solar lines simulation (solar lines often produce significant interferences in the OCS microwindows). The strongest lines of the nu3 fundamental band of OCS at 2062 cm-1 have been systematically evaluated with objective criteria to select a new set of microwindows, assuming the HITRAN 2004 spectroscopic parameters with an increase in the OCS line intensities of the nu3band main isotopologue 16O12C32S by 15.79% as compared to HITRAN 2000 (Rothman et al., 2008, and references therein). Two regularization schemes have further been compared (deducted from ATMOS and ACE-FTS measurements or based on a Tikhonov approach), in order to select the one which optimizes the information content while minimizing the error budget. The selected approach has allowed us to determine updated OCS long-term trend from 1988 to 2009 in both the troposphere and the stratosphere, using spectra recorded on a regular basis with Fourier Transform Infrared spectrometers (FTIRs), under clear-sky conditions, at the NDACC site (Network for the Detection of Atmospheric Composition Change, visit http://www.ndacc.org) of the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580m asl). Trends and seasonal cycles deduced from our results will be compared to values published in the literature and critically discussed. In particular, we will confirm the recent change in the OCS total column trend, which has become positive since 2002 before undergoing a slowing down over the last years. [less ▲]

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See detailTrends of CO2, CH4 and N2O over 1985-2010 from high-resolution FTIR solar observations at the Jungfraujoch station
Duchatelet, Pierre ULg; Mahieu, Emmanuel ULg; Zander, Rodolphe ULg et al

in Geophysical Research Abstracts (2010), 12(EGU2010-15418-2),

Two state-of-the-art Fourier Transform Infrared (FTIR) spectrometers are operated at the Jungfraujoch station (46.5ºN, 8.0ºE, 3580m asl) within the framework of the Network for the Detection of ... [more ▼]

Two state-of-the-art Fourier Transform Infrared (FTIR) spectrometers are operated at the Jungfraujoch station (46.5ºN, 8.0ºE, 3580m asl) within the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). The earliest FTIR observations have been obtained there in 1984. Since then, regular recordings of high-resolution solar absorption spectra have been performed at that site, under clear-sky conditions, allowing to collect almost 29000 observations relevant to the present communication. We present time series of three greenhouse gases targeted by the Kyoto Protocol: CO2, CH4 (and its isotopologue 13CH4) and N2O. These data sets have been obtained with the SFIT-2 algorithm which implements the Optimal Estimation Method of Rodgers (1990). This allows retrieving total columns of the target gases as well as information on their distribution with altitude. For the methane isotopologues and N2O, a Tikhonov L1 regularization scheme has been applied, as part of an harmonization effort carried out within the European HYMN project (see also Dils et al, 2010; Foster et al., 2010). Trends –and their associated uncertainties– characterizing these long series as well as the seasonal modulations have been determined with a statistical tool using bootstrap resampling (Gardiner et al., 2008). Trend values will be presented and critically discussed; in particular, we will investigate if significant changes in the rate of accumulations of these four atmospheric gases occurred over the last 25 years. Numerous additional greenhouse gases are accessible to the FTIR technique. Examples of such trend studies are reported at the EGU General Assembly by Mahieu et al. (2010) and Rinsland et al. (2010). [less ▲]

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See detailHydrogen fluoride total and partial column time series above the Jungfraujoch from long-term FTIR measurements: Impact of the line-shape model, characterization of the error budget and seasonal cycle, and comparison with satellite and model data
Duchatelet, Pierre ULg; Demoulin, Philippe ULg; Hase, Frank et al

in Journal of Geophysical Research. Atmospheres (2010), 115

Time series of hydrogen fluoride (HF) total columns have been derived from ground-based Fourier transform infrared (FTIR) solar spectra recorded between March 1984 and December 2009 at the International ... [more ▼]

Time series of hydrogen fluoride (HF) total columns have been derived from ground-based Fourier transform infrared (FTIR) solar spectra recorded between March 1984 and December 2009 at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0°E, 3580 m asl) with two high resolution spectrometers (one home-made and one Bruker 120-HR). Solar spectra have been inverted with the PROFFIT 9.5 algorithm, using the optimal estimation method. An inter-comparison of HF total columns retrieved with PROFFIT and SFIT-2 – the other reference algorithm in the FTIR community - is performed for the first time. The effect of a Galatry line shape model on HF retrieved total columns and vertical profiles, on the residuals of the fits and on the error budget is also quantified. Information content analysis indicates that, in addition to HF total vertical abundance, three independent stratospheric HF partial columns can be derived from our Bruker spectra. A complete error budget has been established and indicates that the main source of systematic error is linked to HF spectroscopy and that the random error affecting our HF total columns does not exceed 2.5%. Ground-based middle and upper stratospheric HF amounts have been compared to satellite data collected by the HALOE or ACE-FTS instruments. Comparisons of our FTIR HF total and partial columns with runs performed by two 3D numerical models (SLIMCAT and KASIMA) are also included. Finally, FTIR and model HF total and partial columns time series have been analyzed to derive the main characteristics of their seasonal cycles. [less ▲]

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See detailAn approach to retrieve information on the carbonyl fluoride (COF2) vertical distributions above Jungfraujoch by FTIR multi-spectrum multi-window fitting
Duchatelet, Pierre ULg; Mahieu, Emmanuel ULg; Ruhnke, Roland et al

in Atmospheric Chemistry and Physics (2009), 9

We present an original multi-spectrum fitting procedure to retrieve volume mixing ratio (VMR) profiles of carbonyl fluoride (COF2) from ground-based high resolution Fourier transform infrared (FTIR) solar ... [more ▼]

We present an original multi-spectrum fitting procedure to retrieve volume mixing ratio (VMR) profiles of carbonyl fluoride (COF2) from ground-based high resolution Fourier transform infrared (FTIR) solar spectra. The multi-spectrum approach consists of simultaneously combining, during the retrievals, all spectra recorded consecutively during the same day and with the same resolution. Solar observations analyzed in this study with the SFIT-2 v3.91 fitting algorithm correspond to more than 2900 spectra recorded between January 2000 and December 2007 at high zenith angles, with a Fourier Transform Spectrometer operated at the high-altitude International Scientific Station of the Jungfraujoch (ISSJ, 46.5° N latitude, 8.0° E longitude, 3580 m altitude), Switzerland. The goal of the retrieval strategy described here is to provide information about the vertical distribution of carbonyl fluoride. The microwindows used are located in the ν4 or in the ν4 COF2 infrared (IR) absorption bands. Averaging kernel and eigenvector analysis indicates that our FTIR retrieval is sensitive to COF2 inversion between 17 and 30 km, with the major contribution to the retrieved information always coming from the measurement. Moreover, there was no significant bias between COF2 partial columns, total columns or VMR profiles retrieved from the two bands. For each wavenumber region, a complete error budget including all identified sources has been carefully established. In addition, comparisons of FTIR COF2 17–30 km partial columns with KASIMA and SLIMCAT 3-D CTMs are also presented. If we do not notice any significant bias between FTIR and SLIMCAT time series, KASIMA COF2 17–30 km partial columns are lower of around 25%, probably due to incorrect lower boundary conditions. For each times series, linear trend estimation for the 2000–2007 time period as well as a seasonal variation study are also performed and critically discussed. For FTIR and KASIMA time series, very low COF2 growth rates (0.4±0.2%/year and 0.3±0.2%/year, respectively) have been derived. However, the SLIMCAT data set gives a slight negative trend (−0.5±0.2%/year), probably ascribable to discontinuities in the meteorological data used by this model. We further demonstrate that all time series are able to reproduce the COF2 seasonal cycle, which main seasonal characteristics deduced from each data set agree quite well. [less ▲]

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See detailTechnical Note: Harmonized retrieval of column-integrated atmospheric water vapor from the FTIR network - First examples for long-term records and station trends
Sussmann, R.; Borsdorff, T.; Rettinger, M. et al

in Atmospheric Chemistry and Physics (2009), 9(22), 8987-8999

We present a method for harmonized retrieval of integrated water vapor (IWV) from existing, long-term, measurement records at the ground-based mid-infrared solar FTIR spectrometry stations of the Network ... [more ▼]

We present a method for harmonized retrieval of integrated water vapor (IWV) from existing, long-term, measurement records at the ground-based mid-infrared solar FTIR spectrometry stations of the Network for the Detection of Atmospheric Composition Change (NDACC). Correlation of IWV from FTIR with radiosondes shows an ideal slope of 1.00(3). This optimum matching is achieved via tuning one FTIR retrieval parameter, i.e., the strength of a Tikhonov regularization constraining the derivative (with respect to height) of retrieved water profiles given in per cent difference relative to an a priori profile. All other FTIR-sonde correlation parameters (intercept = 0.02(12) mm, bias = 0.02(5) mm, standard deviation of coincident IWV differences (stdv) = 0.27 mm, R = 0.99) are comparable to or better than results for all other ground-based IWV sounding techniques given in the literature. An FTIR-FTIR side-by-side intercomparison reveals a strong exponential increase in stdv as a function of increasing temporal mismatch starting at Δt ≈ 1 minute. This is due to atmospheric water vapor variability. Based on this result we derive an upper limit for the precision of the FTIR IWV retrieval for the smallest Δt (= 3.75 min) still giving a statistically sufficient sample (32 coincidences), i.e., precision (IWVFTIR) < 0.05 mm (or 2.2 % of the mean IWV). The bias of the IWV retrievals from the two different FTIR instruments is nearly negligible (0.02(1) mm). The optimized FTIR IWV retrieval is set up in the standard NDACC algorithm SFIT 2 without changes to the code. A concept for harmonized transfer of the retrieval between different stations deals with all relevant control parameters; it includes correction for differing spectral point spacings (via regularization strength), and final quality selection of the retrievals (excluding the highest residuals (measurement minus model), 5% of the total). As first application examples long-term IWV data sets are retrieved from the FTIR records of the Zugspitze (47.4 °N, 11.0 °E, 2964 m a.s.l.) and Jungfraujoch (46.5 °N, 8.0 °E, 3580 m a.s.l.) NDACC sites. Station-trend analysis comprises a linear fit after subtracting an intra-annual model (3 Fourier components) and constructing an uncertainty interval [95 % confidence] via bootstrap resampling. For the Zugspitze a significant trend of 0.79 [0.65, 0.92] mm/decade is found for the time interval [1996 - 2008], whereas for the Jungfraujoch no significant trend is found. This confirms recent findings that strong variations of IWV trends do occur above land on the local to regional scale (≈250 km) in spite of homogeneous surface temperature trends. This paper provides a basis for future exploitation of more than a dozen existing, multi-decadal FTIR measurement records around the globe for climate studies. [less ▲]

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See detailTrend of lower stratospheric methane (CH4) from Atmospheric Chemistry Experiment (ACE) and Atmospheric Trace Molecule Spectroscopy (ATMOS) measurements
Rinsland, Curtis P.; Chiou, Linda S.; Boone, C. D. et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2009), 110(13), 1066-1071

The long-term trend of methane (CH4) in the lower stratosphere has been estimated for the 1985 to 2008 time period by combining spaceborne solar occultation measurements recorded with high spectral ... [more ▼]

The long-term trend of methane (CH4) in the lower stratosphere has been estimated for the 1985 to 2008 time period by combining spaceborne solar occultation measurements recorded with high spectral resolution Fourier transform spectrometers (FTSs). Volume mixing ratio (VMR) FTS measurements from the ATMOS (Atmospheric Trace Molecule Spectroscopy) FTS covering 120-10 hPa (~16 to 30 km altitude) at 25°N-35°N latitude from 1985 and 1994 have been combined with Atmospheric Chemistry Experiment (ACE) SCISAT-1 FTS measurements covering the same latitude and pressure range from 2004 to 2008. The CH4 trend was estimated by referencing the VMRs to those measured for the long-lived constituent N2O to account for the dynamic history of the sampled airmasses. The combined measurement set shows that the VMR increase measured by ATMOS has been replaced by a leveling off during the ACE measurement time period. Our conclusion is consistent with both remote sensing and in situ measurements of the CH4 trend obtained over the same time span. [less ▲]

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See detailTime series of 12CO and 13CO at northern mid-latitudes: Determination of Partial Column and δ13C seasonal and interannual variations
Mahieu, Emmanuel ULg; Duchatelet, Pierre ULg; Rinsland, C. P. et al

in Geophysical Research Abstracts (2009, April), 11(EGU2009-10017-1),

Carbon monoxide (CO) is an important reactive gas in the troposphere. It is emitted at the ground level by fossil fuel combustion and biomass burning. Biogenic sources and oceans as well as oxidation of ... [more ▼]

Carbon monoxide (CO) is an important reactive gas in the troposphere. It is emitted at the ground level by fossil fuel combustion and biomass burning. Biogenic sources and oceans as well as oxidation of methane and nonmethane hydrocarbons complete the emissions budget. Large uncertainties still affect the relative contributions of the identified anthropogenic and natural sources. Destruction by the hydroxyl radical (OH) is the main removal process for CO in both the troposphere and the stratosphere. The resulting average tropospheric lifetime of CO varies from several weeks to a few months. Two approaches have been developed and optimized to independently retrieve abundances of 12CO and 13CO from high-resolution ground-based infrared solar spectra, using sets of carefully selected lines and the SFIT-2 (v3.91) algorithm which implements the optimal estimation method. The corresponding products will be described and characterized in terms of error budget and information content. These strategies have allowed us to produce partial column time series of 12CO and 13CO, using spectra recorded on a regular basis at the Jungfraujoch station (46.5ºN, 8.0ºE, 3580 m asl, Swiss Alps), a site of the Network for the Detection of Atmospheric Composition Change (NDACC). The seasonal and interannual changes observed in the 12CO,13CO and δ13C (13C/12C) data sets will be presented and discussed. Complementary zonal mean time series derived from occultation measurements collected by the ACE-FTS instrument onboard the Canadian SCISAT-1 platform since 2004 will also be included and analyzed, focusing on the upper troposphere-lower stratosphere region of the atmosphere. Finally, we will use GEOS-Chem 3-D chemistry transport model results to help in the interpretation of the short and long-term variations characterizing the ground-based and satellite data sets, focusing on the factors influencing the partitioning between the two CO isotopologues. [less ▲]

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