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See detailCarbon monoxide retrieved from ground based FTIR remote sensing in the mid-­‐ and near infrared spectral region
Petri, Christof; Blumenstock, Thomas; Hase, Frank et al

Conference (2014, May 14)

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See detailOzone tropospheric and stratospheric trends (1995-2012) at six ground-based FTIR stations (28°N to 79°N)
Vigouroux, Corinne; De Mazière, Martine; Demoulin, Philippe ULg et al

Poster (2013, April)

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

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

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

Poster (2012, August)

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

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

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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 detailOzone tropospheric and stratospheric trends (1995-2011) at six ground- based FTIR stations (34°S to 79°N)
Vigouroux, Corinne; Demoulin, Philippe ULg; Hase, Frank et al

Poster (2011, November)

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

Five ground-based stations in Western Europe, from 79°N to 28°N, all part of the Network for the Detection of Atmospheric Composition Change (NDACC), have joined their efforts to homogenize and optimize the retrievals of ozone profiles from FTIR (Fourier transform infrared) solar absorption spectra. Using the optimal estimation method, distinct vertical information can be obtained in four layers: ground—10 km, 10—18 km, 18—27 km, and 27—42 km, in addition to total column amounts. A bootstrap resampling method has been implemented to determine annual partial and total column trends. Vigouroux et al. (2008) applied this method to the ozone data and discussed the trends of the total columns and of the partial columns in the above four layers, over the period 1995-2004. The updated trends for the 1995-2009 period has been published in the WMO 2010 report. Here, we present the updated trends for the 1995-mid-2011 period, for the five European stations but also for a southern hemisphere station, Wollongong (34°S), which recently joined this ozone network. [less ▲]

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See detailScientific Assessment of Ozone Depletion: 2010, Chapter 2 - Stratospheric Ozone and Surface Ultraviolet Radiation
Douglass, A.; Fioletov, V.; Godin-Beekmann, Sophie et al

Report (2011)

As a result of the Montreal Protocol, ozone is expected to recover from the effect of ozone-depleting substances (ODSs) as their abundances decline in the coming decades. The 2006 Assessment showed that ... [more ▼]

As a result of the Montreal Protocol, ozone is expected to recover from the effect of ozone-depleting substances (ODSs) as their abundances decline in the coming decades. The 2006 Assessment showed that globally averaged column ozone ceased to decline around 1996, meeting the criterion for the first stage of recovery. Ozone is expected to increase as a result of continued decrease in ODSs (second stage of recovery). This chapter discusses recent observations of ozone and ultraviolet radiation in the context of their historical records. Natural variability, observational uncertainty, and stratospheric cooling necessitate a long record in order to attribute an ozone increase to decreases in ODSs. The primary tools used in this Assessment for prediction of ozone are chemistry-climate models (CCMs). These CCMs are designed to represent the processes determining the amount of stratospheric ozone and its response to changes in ODSs and greenhouse gases. Eighteen CCMs have been recently evaluated using a variety of process-based compari-sons to measurements. The CCMs are further evaluated here by comparison of trends calculated from measurements with trends calculated from simulations designed to reproduce ozone behavior during an observing period. [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 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 detailTrend analysis of greenhouse gases over Europe measured by a network of ground-based remote FTIR instruments
Gardiner, Tom; Forbes, A.; De Mazière, Martine et al

in Atmospheric Chemistry and Physics (2008), 8(22), 6719-6727

This paper describes the statistical analysis of annual trends in long term datasets of greenhouse gas measurements taken over ten or more years. The analysis technique employs a bootstrap resampling ... [more ▼]

This paper describes the statistical analysis of annual trends in long term datasets of greenhouse gas measurements taken over ten or more years. The analysis technique employs a bootstrap resampling method to determine both the long-term and intra-annual variability of the datasets, together with the uncertainties on the trend values. The method has been applied to data from a European network of ground-based solar FTIR instruments to determine the trends in the tropospheric, stratospheric and total columns of ozone, nitrous oxide, carbon monoxide, methane, ethane and HCFC-22. The suitability of the method has been demonstrated through statistical validation of the technique, and comparison with ground-based in-situ measurements and 3-D atmospheric models. [less ▲]

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See detailValidation of SCIAMACHY CH4 scientific products using ground-based FTIR measurements
Dils, Bart; De Mazière, Martine; Vigouroux, Corinne et al

Poster (2008, September)

In the framework of the past EVERGREEN project, the development of three scientific algorithms, namely WFM-DOAS (henceforward called WFMD), IMAP-DOAS (henceforward called IMAP) and IMLM, commenced in ... [more ▼]

In the framework of the past EVERGREEN project, the development of three scientific algorithms, namely WFM-DOAS (henceforward called WFMD), IMAP-DOAS (henceforward called IMAP) and IMLM, commenced in order to retrieve the total column amounts of key atmospheric trace gases, including CH4, from SCIAMACHY nadir observations in its near-infrared channels. Since then, the retrieval products of these three algorithms, have undergone serious improvements. At key phases in their development, the products have been validated by using a network of ground-based FTIR instruments. Parallel with the improved SCIAMACHY data, the FTIR groups have taken steps to optimise and harmonise their own datasets and as such the different validation efforts always used the state-of-the-art FTIR dataset. Here we present an overview of the evolution of the CH4 algorithms by re-validating the data, using the same FTIR dataset (as developed under the UFTIR project) for all algorithm versions. [less ▲]

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See detailSatellite validation of column-averaged methane on global scale: ground-based data from 15 FTIR stations versus last generation ENVISAT/SCIAMACHY retrievals
Sussmann, Ralf; Foster, Frank; Borsdorff, Tobias et al

Poster (2008, September)

Previous work has shown that the precision of ground-based mid-infrared (MIR) FTIR spectrometry is sufficient to detect day-to-day variability of columnar methane, while first retrievals from ENVISAT ... [more ▼]

Previous work has shown that the precision of ground-based mid-infrared (MIR) FTIR spectrometry is sufficient to detect day-to-day variability of columnar methane, while first retrievals from ENVISAT/SCIAMACHY (channel 8) satellite measurements were impacted by a significant time-dependent bias due to detector icing. This prevented insight into true methane temporal variability at that time. The goal of our updated study is to investigate the precision of the last generation (channel 6) SCIAMACHY retrievals IMAP-DOAS v49 and WFM-DOAS v1.0 in comparison to retrievals from ground-based MIR measurements of the European FTIR network. We first briefly discuss the origin and magnitude of the natural variability of columnar methane. Subsequently, our study investigates all factors which can be optimized to improve precision of ground-based MIR-FTIR retrievals of columnar methane. This includes an optimized Tikhonov-type regularization tuned in a way to minimize the diurnal variability of retrieved columnar methane. We also discuss ways to select and average individual-pixel satellite data in order to reflect true day-to-day variability and make them comparable to ground-based data. [less ▲]

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See detailImpact of different spectroscopic datasets on CH4 retrievals from Jungfraujoch FTIR spectra
Duchatelet, Pierre ULg; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

Poster (2008, August)

Methane (CH4) is released in the atmosphere by natural processes (e.g. wetlands, termites) as well as by anthropogenic activities (e.g. fossil fuel exploitation, rice agriculture, biomass burning, etc ... [more ▼]

Methane (CH4) is released in the atmosphere by natural processes (e.g. wetlands, termites) as well as by anthropogenic activities (e.g. fossil fuel exploitation, rice agriculture, biomass burning, etc). Due to its high warming potential and its relatively long chemical lifetime (~9 years), atmospheric methane plays a major role in the radiative forcing responsible of the greenhouse effect. Methane also affects climate by influencing tropospheric ozone and stratospheric water. The cycle of methane is complex and to understand it requires a complete study of its emissions and its budget of sources and sinks. High quality methane data sets are needed to perform such studies. CH4 vertical distributions as well as total and partial column time series can be retrieved from high-resolution ground-based FTIR spectra, using, e.g., the SFIT-2 algorithm which implements the Optimal Estimation Method of Rodgers. A set of 5 microwindows - located in the 2 to 5.5 µm range and jointly adopted by all partners involved in the European HYMN project (www.knmi.nl/samenw/hymn/) - are fitted simultaneously during the retrieval procedure. Although this approach provides relatively high information content, CH4 retrieved profiles very often present large oscillations in the troposphere, which might result partly from inappropriate or inconsistent spectroscopic parameters. Significant improvements on retrieval quality could be reached by using more accurate CH4 spectroscopic parameters. This contribution compares 3 different sets of CH4 spectroscopic parameters (including HITRAN 2004 and 2 versions where HITRAN 2004 have been updated by recent laboratory measurements), which have been tested using one year of high resolution FTIR solar observations performed at the International Scientific Station of the Jungfraujoch (Swiss Alps, 46.5°N, 8.0 °E, 3580m a.s.l.). The impact of these different spectroscopic datasets on retrieved CH4 partial columns and vertical profiles, as well as on the fitting quality (residuals) and on the error budget characterizing our CH4 products will be evaluated and discussed. [less ▲]

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See detailValidation of HNO3, ClONO2, and N2O5 from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS)
Wolff, Mareile; Kerzenmacher, Tobias; Strong, Kimberley et al

in Atmospheric Chemistry and Physics (2008), 8(13), 3529-3562

The Atmospheric Chemistry Experiment (ACE) satellite was launched on 12 August 2003. Its two instruments measure vertical profiles of over 30 atmospheric trace gases by analyzing solar occultation spectra ... [more ▼]

The Atmospheric Chemistry Experiment (ACE) satellite was launched on 12 August 2003. Its two instruments measure vertical profiles of over 30 atmospheric trace gases by analyzing solar occultation spectra in the ultraviolet/visible and infrared wavelength regions. The reservoir gases HNO3, ClONO2, and N2O5 are three of the key species provided by the primary instrument, the ACE Fourier Transform Spectrometer (ACE-FTS). This paper describes the ACE-FTS version 2.2 data products, including the N2O5 update, for the three species and presents validation comparisons with available observations. We have compared volume mixing ratio (VMR) profiles of HNO3, ClONO2, and N2O5 with measurements by other satellite instruments (SMR, MLS, MIPAS), aircraft measurements (ASUR), and single balloon-flights (SPIRALE, FIRS-2). Partial columns of HNO3 and ClONO2 were also compared with measurements by ground-based Fourier Transform Infrared (FTIR) spectrometers. Overall the quality of the ACE-FTS v2.2 HNO3 VMR profiles is good from 18 to 35 km. For the statistical satellite comparisons, the mean absolute differences are generally within ±1 ppbv ±20%) from 18 to 35 km. For MIPAS and MLS comparisons only, mean relative differences lie within±10% between 10 and 36 km. ACE-FTS HNO3 partial columns (~15–30 km) show a slight negative bias of −1.3% relative to the ground-based FTIRs at latitudes ranging from 77.8° S–76.5° N. Good agreement between ACE-FTS ClONO2 and MIPAS, using the Institut für Meteorologie und Klimaforschung and Instituto de Astrofísica de Andalucía (IMK-IAA) data processor is seen. Mean absolute differences are typically within ±0.01 ppbv between 16 and 27 km and less than +0.09 ppbv between 27 and 34 km. The ClONO2 partial column comparisons show varying degrees of agreement, depending on the location and the quality of the FTIR measurements. Good agreement was found for the comparisons with the midlatitude Jungfraujoch partial columns for which the mean relative difference is 4.7%. ACE-FTS N2O5 has a low bias relative to MIPAS IMK-IAA, reaching −0.25 ppbv at the altitude of the N2O5 maximum (around 30 km). Mean absolute differences at lower altitudes (16–27 km) are typically −0.05 ppbv for MIPAS nighttime and ±0.02 ppbv for MIPAS daytime measurements. [less ▲]

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See detailMeasured and modeled trends of stratospheric Cly and Fy column amounts in the northern hemisphere
Ruhnke, Roland; Blumenstock, Thomas; Borsdorff, Tobias et al

Poster (2008, July)

The german HGF virtual institute PEP (Pole-Equator-Pole) has been established in 2004 in order to investigate the variability of atmospheric trace constituents along a north-south transection. Within PEP ... [more ▼]

The german HGF virtual institute PEP (Pole-Equator-Pole) has been established in 2004 in order to investigate the variability of atmospheric trace constituents along a north-south transection. Within PEP the HGF centres AWI and FZK as well as the german Universities of Bremen, Karlsruhe and Potsdam combine their knowledge and capabilities in ground-based measurements and global and regional modelling of atmospheric trace constituents and aerosols. Here we present results of long-term measurements of the stratospheric column of HCl, ClONO2, HF, and O3 obtained at the different PEP stations in the northern hemisphere and in addtion at Jungfraujoch. All stations are affiliated to the NDACC (Network for the Detection of Atmospheric Composition Change). The measured time series are compared with long-term model calculations performed with a state of the art 2-D model of the University of Bremen and the 3-D CTM KASIMA. Please note, that the lowest altitude for the determination of the total columns is about 7 km leading to a slight underestimation w.r.t. the measurements. [less ▲]

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See detailCO measurements from the ACE-FTS satellite instrument: data analysis and validation using ground-based, airborne and spaceborne observations
Clerbaux, Catherine; George, Maya; Turquety, Solène et al

in Atmospheric Chemistry and Physics (2008), 8

The Atmospheric Chemistry Experiment (ACE) mission was launched in August 2003 to sound the atmosphere by solar occultation. Carbon monoxide (CO), a good tracer of pollution plumes and atmospheric ... [more ▼]

The Atmospheric Chemistry Experiment (ACE) mission was launched in August 2003 to sound the atmosphere by solar occultation. Carbon monoxide (CO), a good tracer of pollution plumes and atmospheric dynamics, is one of the key species provided by the primary instrument, the ACE-Fourier Transform Spectrometer (ACE-FTS). This instrument performs measurements in both the CO 1-0 and 2-0 ro-vibrational bands, from which vertically resolved CO concentration profiles are retrieved, from the mid-troposphere to the thermosphere. This paper presents an updated description of the ACE-FTS version 2.2 CO data product, along with a comprehensive validation of these profiles using available observations (February 2004 to December 2006). We have compared the CO partial columns with ground-based measurements using Fourier transform infrared spectroscopy and millimeter wave radiometry, and the volume mixing ratio profiles with airborne (both high-altitude balloon flight and airplane) observations. CO satellite observations provided by nadir-looking instruments (MOPITT and TES) as well as limb-viewing remote sensors (MIPAS, SMR and MLS) were also compared with the ACE-FTS CO products. We show that the ACE-FTS measurements provide CO profiles with small retrieval errors (better than 5% from the upper troposphere to 40 km, and better than 10% above). These observations agree well with the correlative measurements, considering the rather loose coincidence criteria in some cases. Based on the validation exercise we assess the following uncertainties to the ACE-FTS measurement data: better than 15% in the upper troposphere (8–12 km), than 30% in the lower stratosphere (12–30 km), and than 25% from 30 to 100 km. [less ▲]

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See detailImpact of different spectroscopic datasets on CH4 retrievals from Jungfraujoch FTIR spectra
Duchatelet, Pierre ULg; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

(2008)

Due to its high warming potential and its relatively long chemical lifetime (~9 years), atmospheric methane (CH4) plays a major role in the radiative forcing responsible of the greenhouse effect. Methane ... [more ▼]

Due to its high warming potential and its relatively long chemical lifetime (~9 years), atmospheric methane (CH4) plays a major role in the radiative forcing responsible of the greenhouse effect. Methane also affects climate by influencing tropospheric ozone and stratospheric water. High quality methane data sets are needed to understand its cycle and evaluate its budget of sources and sinks. Methane vertical distribution as well as total and partial column time series can be retrieved from high-resolution ground-based FTIR spectra, using, e.g., the SFIT-2 algorithm which implements the Optimal Estimation Method of Rodgers . However, although several retrieval approaches characterized by relatively high information content exist, methane retrieved profiles very often present large oscillations in their tropospheric range, which might result partly from inappropriate or inconsistent parameters. Significant improvements on retrieval quality should therefore be reached by using more accurate or compatible CH4 spectroscopic data. The main purpose of this contribution is to test and compare three different sets of CH4 spectroscopic parameters and to quantify their impact on CH4 retrieved products as well as on the fitting quality. [less ▲]

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See detailMeasured and modelled trends of stratopsheric Cly and Fy column amounts in the northern hemisphere
Ruhnke, Roland; Blumenstock, Thomas; Duchatelet, Pierre ULg et al

Poster (2007, April)

Reactive inorganic chlorine plays a crucial role in the stratospheric ozone depletion. To stabilize and enable a recovering of the stratospheric ozone layer, the Montreal protocol and its amendments and ... [more ▼]

Reactive inorganic chlorine plays a crucial role in the stratospheric ozone depletion. To stabilize and enable a recovering of the stratospheric ozone layer, the Montreal protocol and its amendments and adjustments have been progressively implemented to reduce or even stop the production and emission of important chlorinated source gases (CFCs, HCFCs, CCl4, CH3CCl3, and Halons). As these source gases are photolysed in the stratosphere into inorganic chlorine and fluorine, respectively, the turn over of the inorganic chlorine (HCl and ClONO2) and slowing down of fluorine (HF and COF2) reservoirs act as a verification of the effectiveness of these protocols. Here we present results of long-term measurements of the stratospheric column of HCl, ClONO2, and HF obtained at different stations in the northern hemisphere (Ny Alesund, Kiruna, Zugspitze, Jungfraujoch, Izana, all affiliated to the NDACC, Network for the Detection of Atmospheric Composition Change) within the PEP (Pole- Equator-Pole) network. These time series are interpreted with model calculations performed with a state of the art 2-D model and the 3-D CTM KASIMA with respect to the determination of the slowing down or turn over, respectively. In addition, trend parameters calculated using different approaches (e.g. linear trend, bootstrap-method) will be presented and intercompared. [less ▲]

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See detailComparisons between ground-based FTIR and MIPAS N2O and HNO3 profiles before and after assimilation in BASCOE
Vigouroux, Corinne; De Mazière, Martine; Errera, Quentin et al

in Atmospheric Chemistry and Physics (2007), 7

Within the framework of the Network for Detection of Atmospheric Composition Change (NDACC), regular ground-based Fourier transform infrared ( FTIR) measurements of many species are performed at several ... [more ▼]

Within the framework of the Network for Detection of Atmospheric Composition Change (NDACC), regular ground-based Fourier transform infrared ( FTIR) measurements of many species are performed at several locations. Inversion schemes provide vertical profile information and characterization of the retrieved products which are therefore relevant for contributing to the validation of MIPAS profiles in the stratosphere and upper troposphere. We have focused on the species HNO3 and N2O at 5 NDACC-sites distributed in both hemispheres, i.e., Jungfraujoch (46.5 degrees N) and Kiruna (68 degrees N) for the northern hemisphere, and Wollongong (34 degrees S), Lauder (45 degrees S) and Arrival Heights (78 degrees S) for the southern hemisphere. These ground-based data have been compared with MIPAS offline profiles (v4.61) for the year 2003, collocated within 1000 km around the stations, in the lower to middle stratosphere. To get around the spatial collocation problem, comparisons have also been made between the same ground-based FTIR data and the corresponding profiles resulting from the stratospheric 4D-VAR data assimilation system BASCOE constrained by MIPAS data. This paper discusses the results of the comparisons and the usefullness of using BASCOE profiles as proxies for MIPAS data. It shows good agreement between MIPAS and FTIR N2O partial columns: the biases are below 5% for all the stations and the standard deviations are below 7% for the three mid-latitude stations, and below 10% for the high latitude ones. The comparisons with BASCOE partial columns give standard deviations below 4% for the mid-latitude stations to less than 8% for the high latitude ones. After making some corrections to take into account the known bias due to the use of different spectroscopic parameters, the comparisons of HNO3 partial columns show biases below 3% and standard deviations below 15% for all the stations except Arrival Heights ( bias of 5%, standard deviation of 21%). The results for this species, which has a larger spatial variability, highlight the necessity of defining appropriate collocation criteria and of accounting for the spread of the observed air-masses. BASCOE appears to have more deficiencies in producing proxies of MIPAS HNO3 profiles compared to N2O, but the obtained standard deviation of less than 10% between BASCOE and FTIR is reasonable. Similar results on profiles comparisons are also shown in the paper, in addition to partial column ones. [less ▲]

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See detailValidation of MIPAS ClONO2 measurements
Hopfner, Michael; von Clarmann, Thomas; Fischer, H. et al

in Atmospheric Chemistry and Physics (2007), 7

Altitude profiles of ClONO2 retrieved with the IMK (Institut fur Meteorologie und Klimaforschung) science-oriented data processor from MIPAS/Envisat (Michelson Interferometer for Passive Atmospheric ... [more ▼]

Altitude profiles of ClONO2 retrieved with the IMK (Institut fur Meteorologie und Klimaforschung) science-oriented data processor from MIPAS/Envisat (Michelson Interferometer for Passive Atmospheric Sounding on Envisat) mid-infrared limb emission measurements between July 2002 and March 2004 have been validated by comparison with balloon-borne (Mark IV, FIRS2, MIPAS-B), airborne (MIPAS-STR), ground-based (Spitsbergen, Thule, Kiruna, Harestua, Jungfraujoch, Izana, Wollongong, Lauder), and spaceborne (ACE-FTS) observations. With few exceptions we found very good agreement between these instruments and MIPAS with no evidence for any bias in most cases and altitude regions. For balloon-borne measurements typical absolute mean differences are below 0.05 ppbv over the whole altitude range from 10 to 39 km. In case of ACE-FTS observations mean differences are below 0.03 ppbv for observations below 26 km. Above this altitude the comparison with ACE-FTS is affected by the photochemically induced diurnal variation of ClONO2. Correction for this by use of a chemical transport model led to an overcompensation of the photochemical effect by up to 0.1 ppbv at altitudes of 30-35 km in case of MIPAS-ACE-FTS comparisons while for the balloon-borne observations no such inconsistency has been detected. The comparison of MIPAS derived total column amounts with ground-based observations revealed no significant bias in the MIPAS data. Mean differences between MIPAS and FTIR column abundances are 0.11 +/- 0.12 x 10(14) cm(-2) (1.0 +/- 1.1%) and -0.09 +/- 0.19 x 10(14) cm(-2) (-0.8 +/- 1.7%), depending on the coincidence criterion applied. chi(2) tests have been performed to assess the combined precision estimates of MIPAS and the related instruments. When no exact coincidences were available as in case of MIPAS-FTIR or MIPAS-ACE-FTS comparisons it has been necessary to take into consideration a coincidence error term to account for chi(2) deviations. From the resulting chi(2) profiles there is no evidence for a systematic over/underestimation of the MIPAS random error analysis. [less ▲]

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See detailOn the line parameters for the X 1sigma+g (1–0) infrared quadrupolar transitions of 14N2
Goldman, Aaron; Tipping, R.H.; Ma, Q. et al

in Journal of Quantitative Spectroscopy & Radiative Transfer (2007), 103

Re-examination of the 14N2 X 1sigma+g (1–0) line parameters in the HITRAN database showed that the vibration–rotation interaction effect on the line intensities has been neglected, and that the halfwidths ... [more ▼]

Re-examination of the 14N2 X 1sigma+g (1–0) line parameters in the HITRAN database showed that the vibration–rotation interaction effect on the line intensities has been neglected, and that the halfwidths are not compatible with experimental and theoretical studies. New line parameters have been generated, which improve the consistency and accuracy in individual N2 line retrievals from atmospheric spectra. Unresolved line shape issues require further studies. [less ▲]

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