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See detailLong-term sediment management for sustainable hydropower
Dewals, Benjamin ULg; Rulot, François ULg; Erpicum, Sébastien ULg et al

in Sayigh, A (Ed.) Comprehensive Renewable Energy. Vol. 6 (2012)

Since the second half of the 20th century and for decades to come, sedimentation in reservoirs is challenging our ability to maintain the storage capacity needed for water supply, flood mitigation and ... [more ▼]

Since the second half of the 20th century and for decades to come, sedimentation in reservoirs is challenging our ability to maintain the storage capacity needed for water supply, flood mitigation and hydroelectricity production. This complex issue needs to be accounted for from the early stages of the design of dams and reservoirs, until the definition of operation rules oriented towards sustainable management of water and sediments. With reference to the widely-used Driver, Pressure, State, Impact, Response (DPSIR) analytical framework (European Commission 2003), the present chapter reviews key figures and trends in worldwide reservoirs sedimentation, as well as analyzes contemporary sediment management strategies. Besides setting some fundamentals of reservoir sedimentation and summarizing up-to-date background information on rate and distribution of loss of storage in the world, we identify some key driving forces of soil erosion, such as land use, urban development, agriculture and deforestation. Main mechanisms of watershed erosion and sediment yield to reservoirs are also discussed, with a focus on their spatial and temporal variation. Means for quantifying the magnitude of this pressure on reservoirs sustainability are presented, including reservoir surveys, fluvial measurements and combined approaches with numerical modelling. After a review of sedimentation impacts, both locally and downstream as well as upstream of the reservoir, we describe current experience and future opportunities of response to reservoir sedimentation. Possible measures are classified into three broad categories: sediment yield reduction, sediment routing (bypass and pass-through) and sediment removal (dredging and flushing). Pro and contras are presented for the different modes of reservoir operation, as well as their expected efficiency and some specific constraints. Predicting the sedimentation pattern as well as grain sorting processes is a prerequisite for developing optimal sediment evacuation strategies, involving for instance flushing operations. Sound modelling of sediment transport and deposition in reservoirs is highlighted as highly beneficial to support sediment management in the perspective of achieving reservoir sustainability. The chapter also illustrates how spatially distributed numerical modelling may succeed in enhancing decision-making for selecting optimal sediment management measures. [less ▲]

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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 ▲]

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See detailA Long-Term Slip-Rate Study Along The North Anatolian Fault, Eksik, Turkey Using Cosmogenic 36Cl
Kozaci, O; Dolan, J; Finkel, R et al

in EOS : Transactions, American Geophysical Union (2004, December)

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See detailLong-term Spectroscopic Variability of Two Oe Stars
Rauw, Grégor ULg; Nazé, Yaël ULg; Marique, P. X. et al

in Information Bulletin on Variable Stars (2007), 5773

HD 45314 and HD 60848 are poorly studied Oe-type stars. Spectroscopic monitoring over 5 years reveals strong variations in the strength of the emission lines and for HD 45314 in the V/R ratio of the ... [more ▼]

HD 45314 and HD 60848 are poorly studied Oe-type stars. Spectroscopic monitoring over 5 years reveals strong variations in the strength of the emission lines and for HD 45314 in the V/R ratio of the double-peaked emissions. Part of these long-term variations could be recurrent. [less ▲]

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See detailLong-term stability of classical photometry
Hensberge, H.; Manfroid, Jean ULg; Sterken, C.

in The Messenger (1992), 70

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See detailLong-term stratospheric carbon tetrafluoride (CF4) increase inferred from 1985-2004 infrared space-based solar occultation measurements
Rinsland, Curtis P.; Mahieu, Emmanuel ULg; Zander, Rodolphe ULg et al

in Geophysical Research Letters (2006), 33(2),

The long-term stratospheric carbon tetrafluoride (CF4) increase has been determined from infrared high spectral resolution solar occultation Fourier transform spectrometer measurements between 3 and 50 ... [more ▼]

The long-term stratospheric carbon tetrafluoride (CF4) increase has been determined from infrared high spectral resolution solar occultation Fourier transform spectrometer measurements between 3 and 50 hPa (similar to 20 to 40 km altitude) and latitudes from 50 degrees N to 50 degrees S during 1985, 1992, 1993, 1994, and 2004. The 1985 to 1994 measurements were recorded from the ATMOS ( Atmospheric Trace MOlecule Spectroscopy) instrument at 0.01 cm(-1) resolution and in 2004 by the Atmospheric Chemistry Experiment ( ACE) instrument at 0.02 cm(-1) resolution. Stratospheric volume mixing ratios, inferred from a polynomial fit to averages from the time periods considered here, increased from 49.37 +/- 2.60 pptv (10(-12) per unit volume) in 1985 to 58.38 +/- 4.14 pptv in 1992, 60.46 +/- 2.97 pptv in 1993, 60.11 +/- 3.60 pptv in 1994 and to 70.45 +/- 3.40 pptv in 2004. The stratospheric CF4 mixing ratio has continued to increase but at a slower rate than in previous years, for example, (1.14 +/- 0.68)% yr(-1) in 2004 as compared to (2.77 +/- 0.47)% yr(-1) in 1985, 1 sigma. Correlations of CF4 with N2O taking into account the increase of N2O with time also show the increase in the stratospheric CF4 burden over the two decade measurement time span. Our space-based measurements show that the slowdown in the rate of CF4 accumulation previously reported from surface measurements through 1997 has propagated to the stratosphere and is continuing. Citation: Rinsland, C. P., E. Mahieu, R. Zander, R. Nassar, P. Bernath, C. Boone, and L. S. Chiou (2006), Long-term stratospheric carbon tetrafluoride (CF4) increase inferred from 1985-2004 infrared space-based solar occultation measurements, Geophys. Res. Lett., 33, L02808, doi:10.1029/2005GL024709. [less ▲]

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See detailLong-term study of biogenic volatile organic compound exchanges in a forest ecosystem
Laffineur, Quentin ULg

Doctoral thesis (2012)

The terrestrial biosphere, especially forest ecosystems, emits large quantities of volatile organic compounds (VOCs) which have a significant impact on the atmosphere’s chemical and physical ... [more ▼]

The terrestrial biosphere, especially forest ecosystems, emits large quantities of volatile organic compounds (VOCs) which have a significant impact on the atmosphere’s chemical and physical characteristics. In particular, VOCs are precursors in the formation of ozone and sec-ondary organic aerosols. Isoprene and monoterpenes dominate the total VOC emissions, and methanol is one of the most abundant atmospheric VOCs due to its longer half-life than the other two. The main objective of this thesis was to investigate (using the eddy covariance technique and a proton-transfer-reaction mass spectrometer) the mechanisms of VOC (isoprene, monoterpene and methanol) emission and/or deposition at the scale of a temperate climate forest ecosystem (Vielsalm, Belgium) comprising several species (Fagus sylvatica, Abies alba, Picea Abies and Pseudotsuga menziessi). The eddy covariance technique is very suitable for studying VOC emission/deposition mechanisms at ecosystem level as it does not interfere with the functioning of the ecosystem and it has very good temporal resolution (half an hour). It was used for several months at the Vielsalm site without any major interruption to the measurements. The first measurement period ran from early July to late November 2009 and the second from late March to late November 2010. As well as measuring the VOC exchanges by eddy covari-ance, the climate parameters controlling the exchange mechanisms were also measured. During both these periods the methanol, acetaldehyde, acetone, isoprene, methyl vinyl ke-tone/methacrolein, monoterpene, acetic acid (2010) and formic acid (2010) fluxes were meas-ured. The highest emission levels observed were isoprene and monoterpenes along with methanol, which unlike the first two also showed depositions. The thesis therefore naturally focused on studying these three fluxes, in view of the important role played by these three compounds in atmospheric chemistry and hence the scientific community’s interest in refining the parametrisation of these compounds’ ecosystem/atmosphere exchange models. The study of the isoprene, monoterpene and methanol fluxes has been written up in three original articles which form the main body of this thesis. Because of the heterogeneity of the ecosystem studied, the first essential study concerned the identification of VOC-emitting species. This was done with the aid of a flux footprint model combined with a map of the species occurring on the site. This analysis showed that the main monoterpene emitter was Fagus sylvatica followed, to a lesser extent, by Abies alba, Picea Abies and Pseudotsuga menziessi. In contrast to the literature, the analysis showed Abies alba to be a probable isoprene emitter but the presence of Picea Abies, a known isoprene emitter, ruled out absolute certainty on that point. The isoprene fluxes were observed by day only, unlike the monoterpene fluxes which were observed both day and night. Diurnal flux analysis clearly showed temperature and light to be the two main variables controlling emissions. Combining this analysis with a study of the close relationship between isoprene/monoterpene emissions and photosynthesis revealed the plants’ de novo biosynthetic production mechanisms, an original aspect at ecosystem scale. From the occurrence of nocturnal monoterpene emissions it was possible to determine that de novo monoterpene production emitted directly into the atmosphere (as in the case of isoprene) was not the only source of the emissions observed. Withdrawals from monoterpene sinks located in plant organs or in the soil can also be monoterpene sources. Studying the relationship between isoprene/monoterpene fluxes and light, distinguishing between cloudy and sunny conditions, showed that for the same light intensity the emissions were higher in cloudy con-ditions than in sunshine. Similarly, a study of the relationship between isoprene fluxes and photosynthesis in cloudy/sunny conditions suggested that de novo isoprene production is greater in leaves above the canopy than in leaves within the canopy. Long-term measurement of isoprene and monoterpene emissions enabled seasonal changes in the mechanisms observed to be studied and more fully understood. As well as providing an understanding of the mechanisms, this research also resulted in quantification of the seasonal changes in the key parameters for modelling isoprene/monoterpene emissions. Methanol exchanges were generally positive (emissions) by day and negative (depositions) at night. Overall, methanol depositions were predominant in summer and autumn but in the mi-nority in spring. On average, the Vielsalm site behaved like a methanol sink, which contradicts all the other research published to date. An original model was developed for identifying the mechanisms responsible for short-term and long-term methanol emissions/depositions. The consistency between the measurements and the model simulations suggested that the main processes controlling methanol exchanges in summer could be attributed, in the short term, to (water-soluble) methanol adsorption/desorption occurring in the films of water on leaf surfaces and/or on the soil surface and, in the long term, to methanol destruction by a biological and/or chemical degradation process also occurring on the surface of leaves and/or the soil. A study of the difference between the measurements and the model, in spring, indicated the possibility of biosynthetic methanol production by the plants. This production was apparently controlled mainly by temperature, but it could not be shown in summer when methanol adsorption/desorption processes dominated. The literature on ecosystem-atmosphere exchanges of isoprene, monoterpenes and, to a lesser extent, methanol is extensive. Nevertheless, what makes this research original is the spatio-temporal scale used. We are in fact working at ecosystem scale, and not at leaf or branch scale as in most other cases. Moreover, our measurements cover a timescale from half an hour to a full growing season, which is rarely found in the literature. This has resulted in a better under-standing of these compounds’ production and exchange mechanisms. To be precise, the methanol flux study is currently unique in its description and understanding of the deposition mechanisms. [less ▲]

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See detailLong-term study of methane and two of its derivatives from solar observations recorded at the Jungfraujoch station
Bader, Whitney ULg

Doctoral thesis (2015)

A long-term study of methane and two of its derivatives, i.e. ethane and methanol from ground-based FTIR solar observations recorded at the high alpine International Scientific Station of the Jungfraujoch ... [more ▼]

A long-term study of methane and two of its derivatives, i.e. ethane and methanol from ground-based FTIR solar observations recorded at the high alpine International Scientific Station of the Jungfraujoch (3580 m a.s.l.) is reported. Those three gases act as tropospheric ozone precursors through their removal pathway and therefore have an impact on air quality. In the stratosphere, methane influences the content of ozone and in the production of water vapor. Moreover, both methane and ethane impact the greenhouse radiative forcing. While the latter is an indirect greenhouse gas because of its sinks, the former is the second most important anthropogenic greenhouse gas after CO2. The primary challenge of this work is the development and optimization of retrieval strategies for the three studied gases from FTIR spectra recorded at the Jungfraujoch station, in the framework of the Network for Detection of Atmospheric Composition Change (NDACC), in order to assess their concentrations in the atmosphere and to study their long-term trend and recent changes as well as their seasonal variations. The development and optimization of a retrieval strategy, based on the selection of the best combination of parameters, aims to limit interferences, minimize residuals, and maximize information content. To this end, the best retrieval strategy has been selected from a great number of available combinations thanks to a method for error analysis developed through this work. A 17-year time series of methanol is presented thanks to the combination of spectral windows for the first time for ground-based observations resulting in the improvement of the information content. We therefore present the first long-term time series of methanol total, lower tropospheric and upper tropospheric–lower stratospheric partial columns. We found no significant long-term trend of methanol but its seasonal cycle shows a high peak-to-peak amplitude of ̴103 % for total columns characterized by minimum values in winter and maximum values during summertime. The presented time series provides a valuable tool for model and satellite validation and complement the few NDACC measurements at northern mid-latitudes. Regarding ethane, we have for the first time included a combination of improved spectroscopic parameters as well as an improved a priori state that substantially reduce fitting residuals and enhance information content. Analysis of the long-term trend of ethane covering 20 years of observations revealed a strong positive trend of ethane from 2009 onwards of ̴5 %/year. We hypothesize that this recent ethane upturn may be the result of a large increase in fugitive emissions from the massive exploitation of shale gas and tight oil reservoirs on the North American continent. Finally, we quantified the changes of methane since 2005 from 10 ground-based NDACC sites, with a mean global increase of 0.30 %/year. Investigations into the source(s) responsible for this re-increase are performed with a GEOS-Chem tagged simulation that provides the contribution of each emission source and one sink to the total methane simulated. From the analysis of the GEOS-Chem tracers on both the local and global scales, we determined that the increasing anthropogenic emissions such as coal mining, gas and oil transport and exploitation, have played a major role in the increase of atmospheric methane observed since 2005 while they are secondary contributors to the total methane budget. [less ▲]

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See detailLong-term treatment of postmenopausal osteoporosis with strontium ranelate: Results at 8 years.
Reginster, Jean-Yves ULg; Bruyère, Olivier ULg; Sawicki, A. et al

in BONE (2009), 45

OBJECTIVES: Strontium ranelate 2 g/day has proven efficacy against vertebral and nonvertebral fracture over 5 years in postmenopausal osteoporosis, though many women require longer-term treatment. This ... [more ▼]

OBJECTIVES: Strontium ranelate 2 g/day has proven efficacy against vertebral and nonvertebral fracture over 5 years in postmenopausal osteoporosis, though many women require longer-term treatment. This article describes the efficacy, safety, and tolerability of this agent over 8 years. METHODS: Postmenopausal osteoporotic women having participated in the 5-year efficacy trials SOTI and TROPOS were invited to enter a 3-year open-label extension study. The results presented here focus on patients who received strontium ranelate for 8 years. RESULTS: At the extension baseline, the population treated for 8 years (n=879; 79.1+/-5.6 years) had femoral neck T-score of -2.61+/-0.71. The cumulative incidences of new vertebral and nonvertebral fractures (13.7% and 12.0%, respectively) over years 6 to 8 were non-statistically different from the cumulative incidences in the first 3 years of the original studies (11.5% and 9.6%). Lumbar spine, femoral neck, and total hip bone mineral density (BMD) increased throughout the 8-year period. Annual relative change in BMD was significant at every visit, except the 8-year visit for femoral neck and total hip BMD. Strontium ranelate was safe and well tolerated over 8 years. CONCLUSIONS: Long-term treatment with strontium ranelate 2 g/day in postmenopausal osteoporotic women leads to continued increases in BMD at all sites. The data also provide some evidence for a sustained antifracture efficacy. [less ▲]

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See detailLong-term treatment of postmenopausal osteoporotic women with strontium ranelate : results at 10 years
Reginster, Jean-Yves ULg; Kaufman, J. M.; Devogelaer, J. D. et al

in Annals of the Rheumatic Diseases (2011), 70(S3), 167

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See detailLong-term treatment with valproic acid does not alleviate the condition of HAM/TSP
Olindo, S.; Belrose, G.; Lezin, A. et al

in AIDS Research and Human Retroviruses (2009, July 01), 25(11), 21

Long-Term Treatment with Valproic Acid Does Not Alleviate the Condition of HAM/TSP Olindo, S.,1 Belrose, G.,2 Lezin, A.,2 Gillet, N.,3 Defoiche, J.,4 Rodriguez, S.,4 Signaté, A.,1 Verlaeten, O.,4 Smadja ... [more ▼]

Long-Term Treatment with Valproic Acid Does Not Alleviate the Condition of HAM/TSP Olindo, S.,1 Belrose, G.,2 Lezin, A.,2 Gillet, N.,3 Defoiche, J.,4 Rodriguez, S.,4 Signaté, A.,1 Verlaeten, O.,4 Smadja, D.,1 Césaire, R.,2 Willems, L.4 1Service de Neurologie and JE 2503, Centre Hospitalier Universitaire de Fort-de-France, 97200 Fort-de-France, Martinique, France; 2Laboratoire de Virologie-Immunologie and JE 2503, Centre Hospitalier Universitaire de Fort-de-France, 97200 Fort-de-France, Martinique, France; 3Department of Immunology, Imperial College, London, UK; 4Molecular and Cellular Biology, University Academia ‘‘Wallonie-Europe’’, 5030 Gembloux, Belgium. LW is Research Director of the FNRS. We previously proposed to interfere with proviral loads in HAM/TSP patients by modulating lysine deacetylase activity using valproic acid (VPA). The strategy aims at activating viral gene expression in order to expose virus-positive cells to the host immune response. We conducted a single-center, two-year open-label trial, with 19 HAM/TSP volunteers treated with oral doses of VPA (20mg/Kg/day). Objectives were to assess biological response and clinical safety to VPA treatment in HAM/TSP patients. By microarray analysis, we show that VPA treatment moderately stimulated expression of cyclinD2 and Rho GTPase activating protein 18 in CD4-T cells. CD8-mediated lysis efficiency of Tax-expressing cells was unaltered by VPA treatment. The CD4-T cell turnover rate was calculated by GC/MS analysis from quantitative incorporation of deuterium into DNA. Transient increase in proviral loads correlated with accelerated proliferation. After 2 years, the proviral loads reached levels similar to those before treatment. The main clinical side effects were drowsiness (52%), tremor (47%), digestive symptoms (37%), vertigo (26%), and alopecia (10%). The frequency of side symptoms tended to decrease over the trial course. The neurological status over the study constituted the primary clinical safety measures. Disability Status Scale, muscle testing score, Ashworth score, and urinary dysfunction score showed no significant changes. Walking Time Test (WTT) slightly varied over the study except in 3 patients in whom the WTT variation rates were>20%. These 3 patients experienced drowsiness and tremor and improved rapidly after treatment discontinuation. Together, these observations indicated that long term treatment with VPA is safe but does not alleviate the condition of HAM/TSP. [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 detailLong-term trend of CH4 at northern mid-latitudes: Comparison between ground-based infrared solar and surface sampling measurements
Rinsland, Curtis P.; Goldman, Aaron; Elkins, James W. et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2006), 97(3), 457-466

We report average tropospheric CH4 volume mixing ratios retrieved from a 27 year time series of high spectral resolution infrared solar absorption measurements recorded between May 1977 and July 2004 at ... [more ▼]

We report average tropospheric CH4 volume mixing ratios retrieved from a 27 year time series of high spectral resolution infrared solar absorption measurements recorded between May 1977 and July 2004 at the US National Solar Observatory station on Kitt Peak (31.9 degrees N, 111.6 degrees W, 2.09 km altitude) and their comparison with surface in situ sampling measurements recorded between 1983 and 2004 at the Climate Monitoring and Diagnostics Laboratory (CMDL) station at Niwot Ridge, Colorado (40.0 degrees N, 105.5 degrees W, 3013 m altitude). The two measurement sets therefore overlap for the 1983-2004 time period. An average tropospheric volume mixing ratios of 1814 +/- 48 ppbv (1 ppbv = 10(-9) per unit volume) has been derived from the solar absorption time series with a best-fit increase rate trend equal to 8.26 +/- 2.20 ppbv yr(-1) in 1983 decreasing to 1.94 +/- 3.69 ppbv yr(-1) in 2003. The CMDL measurements also show a continuous long-term CH4 volume mixing ratio rise, with subsequent slowing down. A mean ratio of the retrieved average tropospheric volume mixing ratio to the CMDL volume mixing ratio for the overlapping time period of 1.038 +/- 0.034 indicates agreement between both data sets within the quantified experimental errors. (C) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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

Poster (2011, November 10)

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

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

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See detailLong-term trends of inorganic chlorine from ground-based infrared solar spectra: Past increases and evidence for stabilization
Rinsland, Curtis P.; Mahieu, Emmanuel ULg; Zander, Rodolphe ULg et al

in Journal of Geophysical Research (2003), 108(D8), 4252

Long-term time series of hydrogen chloride (HCl) and chlorine nitrate (ClONO2) total column abundances has been retrieved from high spectral resolution ground-based solar absorption spectra recorded with ... [more ▼]

Long-term time series of hydrogen chloride (HCl) and chlorine nitrate (ClONO2) total column abundances has been retrieved from high spectral resolution ground-based solar absorption spectra recorded with infrared Fourier transform spectrometers at nine NDSC (Network for the Detection of Stratospheric Change) sites in both Northern and Southern Hemispheres. The data sets span up to 24 years and most extend until the end of 2001. The time series of Cly (defined here as the sum of the HCl and ClONO2 columns) from the three locations with the longest time-span records show rapid increases until the early 1990s superimposed on marked day-to-day, seasonal and inter-annual variability. Subsequently, the buildup in Cly slows and reaches a broad plateau after 1996, also characterized by variability. A similar time evolution is also found in the total chlorine concentration at 55 km altitude derived from Halogen Occultation Experiment (HALOE) global observations since 1991. The stabilization of inorganic chlorine observed in both the total columns and at 55 km altitude indicates that the near-global 1993 organic chlorine (CCly) peak at the Earth’s surface has now propagated over a broad altitude range in the upper atmosphere, though the time lag is difficult to quantify precisely from the current data sets, due to variability. We compare the three longest measured time series with two-dimensional model calculations extending from 1977 to 2010, based on a halocarbon scenario that assumes past measured trends and a realistic extrapolation into the future. The model predicts broad Cly maxima consistent with the long-term observations, followed by a slow Cly decline reaching 12–14% relative to the peak by 2010. The data reported here confirm the effectiveness of the Montreal Protocol and its Amendments and Adjustments in progressively phasing out the major man-related perturbations of the stratospheric ozone layer, in particular, the anthropogenic chlorine-bearing source gases. [less ▲]

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