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See detailValidation of ACE-FTS v2.2 measurements of HCl, HF, CCl3F and CCl2F2 using space-, balloon- and ground-based instrument observations
Mahieu, Emmanuel ULg; Duchatelet, Pierre ULg; Demoulin, Philippe ULg et al

in Atmospheric Chemistry and Physics (2008), 8

Hydrogen chloride (HCl) and hydrogen fluoride (HF) are respectively the main chlorine and fluorine reservoirs in the Earth's stratosphere. Their buildup resulted from the intensive use of man-made ... [more ▼]

Hydrogen chloride (HCl) and hydrogen fluoride (HF) are respectively the main chlorine and fluorine reservoirs in the Earth's stratosphere. Their buildup resulted from the intensive use of man-made halogenated source gases, in particular CFC-11 (CCl3F) and CFC-12 (CCl2F2), during the second half of the 20th century. It is important to continue monitoring the evolution of these source gases and reservoirs, in support of the Montreal Protocol and also indirectly of the Kyoto Protocol. The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) is a space-based instrument that has been performing regular solar occultation measurements of over 30 atmospheric gases since early 2004. In this validation paper, the HCl, HF, CFC-11 and CFC-12 version 2.2 profile data products retrieved from ACE-FTS measurements are evaluated. Volume mixing ratio profiles have been compared to observations made from space by MLS and HALOE, and from stratospheric balloons by SPIRALE, FIRS-2 and Mark-IV. Partial columns derived from the ACE-FTS data were also compared to column measurements from ground-based Fourier transform instruments operated at 12 sites. ACE-FTS data recorded from March 2004 to August 2007 have been used for the comparisons. These data are representative of a variety of atmospheric and chemical situations, with sounded air masses extending from the winter vortex to summer sub-tropical conditions. Typically, the ACE-FTS products are available in the 10-50 km altitude range for HCl and HF, and in the 7-20 and 7-25 km ranges for CFC-11 and -12, respectively. For both reservoirs, comparison results indicate an agreement generally better than 5-10% above 20 km altitude, when accounting for the known offset affecting HALOE measurements of HCl and HF. Larger positive differences are however found for comparisons with single profiles from FIRS-2 and SPIRALE. For CFCs, the few coincident measurements available suggest that the differences probably remain within +/-20%. [less ▲]

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See detailValidation of ACE-FTS N2O measurements
Strong, Kimberley; Wolff, Mareile A; Kerzenmacher, Tobias E et al

in Atmospheric Chemistry and Physics (2008), 8(16), 4759-4786

The Atmospheric Chemistry Experiment (ACE), also known as SCISAT, was launched on 12 August 2003, carrying two instruments that measure vertical profiles of atmospheric constituents using the solar ... [more ▼]

The Atmospheric Chemistry Experiment (ACE), also known as SCISAT, was launched on 12 August 2003, carrying two instruments that measure vertical profiles of atmospheric constituents using the solar occultation technique. One of these instruments, the ACE Fourier Transform Spectrometer (ACE-FTS), is measuring volume mixing ratio (VMR) profiles of nitrous oxide (N2O) from the upper troposphere to the lower mesosphere at a vertical resolution of about 3-4 km. In this study, the quality of the ACE-FTS version 2.2 N2O data is assessed through comparisons with coincident measurements made by other satellite, balloon-borne, aircraft, and ground-based instruments. These consist of vertical profile comparisons with the SMR, MLS, and MIPAS satellite instruments, multiple aircraft flights of ASUR, and single balloon flights of SPIRALE and FIRS-2, and partial column comparisons with a network of ground-based Fourier Transform InfraRed spectrometers (FTIRs). Between 6 and 30 km, the mean absolute differences for the satellite comparisons lie between -42 ppbv and +17 ppbv, with most within +/- 20 ppbv. This corresponds to relative deviations from the mean that are within +/- 15%, except for comparisons with MIPAS near 30 km, for which they are as large as 22.5%. Between 18 and 30 km, the mean absolute differences for the satellite comparisons are generally within +/- 10 ppbv. From 30 to 60 km, the mean absolute differences are within +/- 4 ppbv, and are mostly between -2 and +1 ppbv. Given the small N2O VMR in this region, the relative deviations from the mean are therefore large at these altitudes, with most suggesting a negative bias in the ACE-FTS data between 30 and 50 km. In the comparisons with the FTIRs, the mean relative differences between the ACE-FTS and FTIR partial columns (which cover a mean altitude range of 14 to 27 km) are within +/- 5.6% for eleven of the twelve contributing stations. This mean relative difference is negative at ten stations, suggesting a small negative bias in the ACE-FTS partial columns over the altitude regions compared. Excellent correlation (R=0.964) is observed between the ACE-FTS and FTIR partial columns, with a slope of 1.01 and an intercept of -0.20 on the line fitted to the data. [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 detailTechnical Note: New ground-based FTIR measurements at Ile de La Réunion: observations, error analysis, and comparisons with independent data
Senten, Cindy; De Mazière, Martine; Dils, Bart et al

in Atmospheric Chemistry and Physics (2008), 8(13), 3483-3508

Ground-based high spectral resolution Fourier-transform infrared (FTIR) solar absorption spectroscopy is a powerful remote sensing technique to obtain information on the total column abundances and on the ... [more ▼]

Ground-based high spectral resolution Fourier-transform infrared (FTIR) solar absorption spectroscopy is a powerful remote sensing technique to obtain information on the total column abundances and on the vertical distribution of various constituents in the atmosphere. This work presents results from two FTIR measurement campaigns in 2002 and 2004, held at Ile de La Réunion (21° S, 55° E). These campaigns represent the first FTIR observations carried out at a southern (sub)tropical site. They serve the initiation of regular, long-term FTIR monitoring at this site in the near future. To demonstrate the capabilities of the FTIR measurements at this location for tropospheric and stratospheric monitoring, a detailed report is given on the retrieval strategy, information content and corresponding full error budget evaluation for ozone (O3), methane (CH4), nitrous oxide (N2O), carbon monoxide (CO), ethane (C2H6), hydrogen chloride (HCl), hydrogen fluoride (HF) and nitric acid (HNO3) total and partial column retrievals. Moreover, we have made a thorough comparison of the capabilities at sea level altitude (St.-Denis) and at 2200 m a.s.l. (Maïdo). It is proved that the performances of the technique are such that the atmospheric variability can be observed, at both locations and in distinct altitude layers. Comparisons with literature and with correlative data from ozone sonde and satellite (i.e., ACE-FTS, HALOE and MOPITT) measurements are given to confirm the results. Despite the short time series available at present, we have been able to detect the seasonal variation of CO in the biomass burning season, as well as the impact of particular biomass burning events in Africa and Madagascar on the atmospheric composition above Ile de La Réunion. We also show that differential measurements between St.-Denis and Maïdo provide useful information about the concentrations in the boundary layer. [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 detailValidation of ACE-FTS v2.2 methane profiles from the upper troposphere to the lower mesosphere
De Mazière, Martine; Vigouroux, Corinne; Bernath, Peter et al

in Atmospheric Chemistry and Physics (2008), 9(9), 2421-2435

The ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) solar occultation instrument that was launched onboard the Canadian SCISAT-1 satellite in August 2003 is measuring vertical ... [more ▼]

The ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) solar occultation instrument that was launched onboard the Canadian SCISAT-1 satellite in August 2003 is measuring vertical profiles from the upper troposphere to the lower mesosphere for a large number of atmospheric constituents. Methane is one of the key species. The version v2.2 data of the ACE-FTS CH4 data have been compared to correlative satellite, balloon-borne and ground-based Fourier transform infrared remote sensing data to assess their quality. The comparison results indicate that the accuracy of the data is within 10% in the upper troposphere – lower stratosphere, and within 25% in the middle and higher stratosphere up to the lower mesosphere (<60 km). The observed differences are generally consistent with reported systematic uncertainties. ACE-FTS is also shown to reproduce the variability of methane in the stratosphere and lower mesosphere. [less ▲]

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See detailObservations of halogens, CO, CH4, and H2CO at Ile de La Réunion from ground-based FTIR and MAXDOAS campaign measurements
De Mazière, Martine; Vigouroux, Corinne; Hendrick, François et al

Poster (2008, April)

Ile de La Réunion is a complementary site in the Network for the Detection of Atmospheric Composition Change (NDACC), situated in the southern tropics, at 21°S, 55°E. In support of a better understanding ... [more ▼]

Ile de La Réunion is a complementary site in the Network for the Detection of Atmospheric Composition Change (NDACC), situated in the southern tropics, at 21°S, 55°E. In support of a better understanding of atmospheric chemistry and physics above tropical regions, we have implemented new ground-based MAX-DOAS (multi-axis DOAS) and FTIR (Fourier transform infrared) observations at this site, on a campaign basis since 2002. At present, we have data from 2002 (month of October), 2004 (August to October) and 2007 (end of May until the end of October). Additional campaigns are planned until the availability of a new infrastructure for permanent observations at the Maido (~ 2000 masl), around 2010. Here, we report on the available time series for a number of tropospheric species (CO, H2CO and CH4,) and stratospheric halogen species, comparisons between MAX-DOAS and FTIR data of H2CO, and comparisons of ground-based and satellite data. [less ▲]

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See detailObservations of CH4, CH3D and H2CO at Ile de La Réunion from ground-based FTIR and MAXDOAS campaign measurements
Vigouroux, Corinne; De Mazière, Martine; Van Roozendael, Michel et al

Poster (2007, November)

Ile de La Réunion (21°S, 55°E) is candidate to become a primary station the ground-based Network for the Detection of Atmospheric Composition Change (NDACC) which was formed to provide long-term ... [more ▼]

Ile de La Réunion (21°S, 55°E) is candidate to become a primary station the ground-based Network for the Detection of Atmospheric Composition Change (NDACC) which was formed to provide long-term monitoring of atmospheric trace gases at globally distributed sites. Ground-based network data are also very valuable for the validation of satellite data, such as SCIAMACHY, ACE-FTS and IASI. Up to now, only a few NDACC stations are located in the Southern Hemisphere, and none of them is at subtropical latitude. Three campaigns of FTIR measurements were made at the Ile de La Réunion in preparation of a near future permanent installation, namely in October 2002, from August to October 2004, and from May to November 2007. A UV-visible Multi-Axis DOAS (MAXDOAS) instrument was operated at the same site from July 2004 to June 2005. The inversion algorithms for both the MAXDOAS and FTIR spectral data analyses use the Optimal Estimation Method to derive information about the vertical distribution of the target gases. We will present the vertical profiles and total columns of the greenhouse gas CH4 and its isotopologue CH3D, obtained from the FTIR measurements. For the latter, the number of degrees of freedom for signal is close to one, limiting the information to the total column abundance. Early comparisons with correlative measurements from satellite data will be discussed. Formaldehyde (H2CO) is a source of HOx and an indicator for biogenic emissions, biomass burning, and anthropogenic pollution. It can be measured by both the FTIR and UV-Visible MAXDOAS instruments. The total columns obtained by the two techniques in the common period of measurements August-October 2004 will be discussed. We will also show the comparisons of the time series for formaldehyde from both instruments with correlative SCIAMACHY data above La Réunion. [less ▲]

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See detailApproaches for retrieving abundances of methane isotopologues in the frame of the AGACC project from ground-based FTIR observations performed at the Jungfraujoch
Duchatelet, Pierre ULg; Mahieu, Emmanuel ULg; Demoulin, Philippe ULg et al

Poster (2007, April)

This work has been performed within the frame of AGACC(http://www.oma.be/AGACC/Home.html), a contribution to the Belgian Scientific Support for a Sustainable Development. The project intends to make an ... [more ▼]

This work has been performed within the frame of AGACC(http://www.oma.be/AGACC/Home.html), a contribution to the Belgian Scientific Support for a Sustainable Development. The project intends to make an advanced exploitation of existing ground-based remote-sensing measurements for a selection of atmospheric species that play an important role in the chemistry of the atmosphere and that have a direct or indirect impact on climate. Target species include -among others- lower tropospheric aerosols, H2O, HDO, CH4, HCN and CO. The instrumentation includes 3 types of spectrometers (FTIR, MAXDOAS and Brewer) and one CIMEL sun photometer. These instruments are operated at 3 different sites (Jungfraujoch, Ile de la Réunion and Uccle) and most of them are affiliated with the Network for the Detection of Atmospheric Composition Change (NDACC, formerly NDSC - http://www.ndacc.org), a group dedicated to performing high-quality long-term observations. This contribution will deal with the detection of the isotopologues of methane, a species released to 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, atmospheric methane is a major greenhouse gas. Methane also affects climate by influencing tropospheric ozone and stratospheric water. The cycle of methane is complex and a thoroughly study of the sources and sinks of its main isotopologue, as well as the other isotopic species, is necessary to characterize it. Isotopic ratios are also useful to differentiate between various sources of atmospheric methane. To study the vertical distribution of methane isotopologues from the high resolution FTIR spectra recorded by the University of Liège instrument at the International Scientific Station of the Jungfraujoch (ISSJ; 46.5°N, 8.0°E, 3580m a.s.l., Swiss Alps), we have selected several 13CH4 lines distributed in the so-called InSb (1-5 µm) and MCT (2-16 µm) spectral ranges. A set of four microwindows has also been selected for the study of CH3D. Using the SFIT-2 v3.91 algorithm, vertical column abundances as well as low-resolution vertical distributions have been retrieved, adjusted from an a priori profile defined on a 41 layers scheme and derived from ACE-FTS space observations. The information content and first preliminary retrieval results will be presented. [less ▲]

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See detailGround-based FTIR measurements at Ile de La Réunion: Observations, error analysis and comparisons with satellite data.
Senten, Cindy; De Mazière, Martine; Hermans, Christian et al

in Geophysical Research Abstracts (2007), 9

Ground-based Fourier-transform infrared (FTIR) spectroscopy is a powerful remote sensing technique to obtain information on the total column abundances and on the vertical distribution of various ... [more ▼]

Ground-based Fourier-transform infrared (FTIR) spectroscopy is a powerful remote sensing technique to obtain information on the total column abundances and on the vertical distribution of various constituents in the atmosphere. Many of these species are essential for the investigation of important atmospheric phenomena, such as the overall greenhouse effect or the stratospheric ozone decrease and recovery. In the frame of the Network for the Detection of Atmospheric Composition Change (NDACC), such observations have been made since many years at several measurement stations for the worldwide long-term monitoring of the atmospheric composition. In this work, we present the results from two short-term FTIR measurement campaigns in 2002 and 2004 at the Ile de La Réunion (21°S, 55°E), a complementary NDACC site in the subtropics, in the Indian Ocean. All spectra were recorded in solar absorption mode. The results discussed here concern the direct greenhouse gases methane (CH4), nitrous oxide (N2O) and ozone (O3), and the indirect greenhouse gases carbon monoxide (CO) and ethane (C2H6), as well as hydrogen cyanide (HCN) and stratospheric hydrogen chloride (HCl), hydrogen fluoride (HF) and nitric acid (HNO3). For the latter species (HCN, HCl, HF and HNO3), we show time series of total column amounts from the surface up to 60 km. For CO, CH4, N2O and O3, it is possible to derive additionally independent information on a few partial columns; these time series are discussed as well. A complete error budget of the retrieval products is given. Temporary mutually correlated enhancements of CO, C2H6and HCN have been observed. They have been traced back to biomass burning events in southern Africa and Madagascar using the FLEXPART model. Comparisons of our retrievals with correlative data from satellite experiments, such as ACE and MOPITT, and with available ozone soundings, show generally good agreements between the different data sets. [less ▲]

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