Rodolphe Zander

University of Liège, Luik, Walloon Region, Belgium

Are you Rodolphe Zander?

Claim your profile

Publications (26)62.72 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Hydrofluorocarbons (HCFCs) are the first substitutes to the long-lived ozone depleting halocarbons, in particular the chlorofluorocarbons (CFCs). Given the complete ban of the CFCs by the Montreal Protocol, its Amendments and Adjustments, HCFCs are on the rise, with current rates of increase substantially larger than at the beginning of the 21st century. HCFC-142b (CH3CClF2) is presently the second most abundant HCFCs, after HCFC-22 (CHClF2). It is used in a wide range of applications, including as a blowing foam agent, in refrigeration and air-conditioning. Its concentration will soon reach 25 ppt in the northern hemisphere, with mixing ratios increasing at about 1.1 ppt/yr [Montzka et al., 2011]. The HCFC-142b lifetime is estimated at 18 years. With a global warming potential of 2310 on a 100-yr horizon, this species is also a potent greenhouse gas [Forster et al., 2007]. First space-based retrievals of HCFC-142b have been reported by Dufour et al. [2005]. 17 occultations recorded in 2004 by the Canadian ACE-FTS instrument (Atmospheric Chemistry Experiment - Fourier Transform Spectrometer, onboard SCISAT-1) were analyzed, using two microwindows (1132.5-1135.5 and 1191.5-1195.5 cm-1). In 2009, Rinsland et al. determined the HCFC-142b trend near the tropopause, from the analysis of ACE-FTS observations recorded over the 2004-2008 time period. The spectral region used in this study extended from 903 to 905.5 cm-1. In this contribution, we will present the first HCFC-142b measurements from ground-based high-resolution Fourier Transform Infrared (FTIR) solar spectra. We use observations recorded at the high altitude station of the Jungfraujoch (46.5°N, 8°E, 3580 m asl), with a Bruker 120HR instrument, in the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). The retrieval of HCFC-142b is very challenging, with simulations indicating only weak absorptions, lower than 1% for low sun spectra and current concentrations. Among the four microwindows tested, the region extending from 900 to 906 cm-1 proved to be the most appropriate, with limited interferences, in particular from water vapor. A total column time series spanning the 2004-2012 time period will be presented, analyzed and critically discussed. After conversion of our total columns to concentrations, we will compare our results with in situ measurements performed in the northern hemisphere by the AGAGE network. Acknowledgments The University of Liège contribution to the present work has primarily been supported by the SSD and PRODEX programs (AGACC-II and A3C projects, respectively) funded by the Belgian Federal Science Policy Office (BELSPO), Brussels. E. Mahieu is Research Associate with the F.R.S. - FNRS. Laboratory developments and mission expenses at the Jungfraujoch station were funded by the F.R.S. - FNRS and the Fédération Wallonie-Bruxelles, respectively. We thank the International Foundation High Altitude Research Stations Jungfraujoch and Gornergrat (HFSJG, Bern) for supporting the facilities needed to perform the observations. We further acknowledge the vital contribution from all the Belgian colleagues in performing the Jungfraujoch observations used here. References Dufour, G., C.D. Boone, and P.F. Bernath, First measurements of CFC-113 and HCFC-142b from space using ACE-FTS infrared spectra, Geophys. Res. Lett., 32, L15S09, doi:10.1029/2005GL022422, 2005. Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland, 2007: Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Montzka, S.A., S. Reimann, A. Engel, K. Krüger, S. O'Doherty, W.T. Sturges, D. Blake, M. Dirf, P. Fraser, L. Froidevaux, K. Jucks, K. Kreher, M.J. Kurylo, A. Mellouki, J. Miller, O.-J. Nielsen, V.L. Orkin, R.G. Prinn, R. Shew, M.L. Santee, A. Stohl, and D. Verdonik, Ozone-Depleting Substances (ODSs) and Related Chemicals, Chapter 1 in Scientific Assessment of Ozone Depletion: 2010, Global Ozone Research and Monitoring Project-Report No. 52, 516 pp., World Meteorological Organization, Geneva, Switzerland, 2011. Rinsland, C.P., L.S. Chiou, C.D. Boone, P.F. Bernath, and E. Mahieu, First Measurements of the HCFC-142b trend from Atmospheric Chemistry Experiment (ACE) Solar Occultation Spectra, J. Quant. Spectrosc. Radiat. Transfer, 110, 2127-2134, 2009.
    04/2013;
  • [Show abstract] [Hide abstract]
    ABSTRACT: The long-term trend of the atmospheric carbon tetrachloride (CCl4) burden has been retrieved from high spectral resolution infrared solar absorption spectra recorded between January 1999 and June 2011. The observations were made 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 spectrometric analysis of the strong CCl4ν3 band at 794 cm−1, accounting for all interfering molecules (e.g., H2O, CO2, O3, and a dozen weakly absorbing gases). A significant improvement in the fitting residuals and in the retrieved CCl4 columns was obtained by taking into account line mixing in a strong interfering CO2 Q branch. This procedure had never been implemented in remote sensing CCl4 retrievals though its importance was noted in earlier studies. A fit to the CCl4 daily mean total column time series returns a statistically-significant long-term trend of (−1.49±0.08×1013 mol/cm2)/yr, 2−σ. This corresponds to an annual decrease of (−1.31±0.07) pptv for the mean free tropospheric volume mixing ratio. Furthermore, the total column data set reveals a weak seasonal cycle with a peak-to-peak amplitude of 4.5%, with minimum and maximum values occurring in mid-February and mid-September, respectively. This small seasonal modulation is attributed primarily to the residual influence of tropopause height changes throughout the year. The negative trend of the CCl4 loading reflects the continued impact of the regulations implemented by the Montreal Protocol and its strengthening amendments and adjustments. Despite this statistically significant decrease, the CCl4 molecule currently remains an important contributor to the atmospheric chlorine budget, and thus deserves further monitoring, to ensure continued compliance with these strengthenings, globally. Our present findings are briefly discussed with respect to recent relevant CCl4 investigations at the ground and from space.
    Journal of Quantitative Spectroscopy and Radiative Transfer 07/2012; 113(11):1322–1329. · 2.29 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The longest series of Fourier Transform Infrared (FTIR) high spectral resolution solar absorption observations are available from the Jungfraujoch and Kitt Peak stations, located at 46.5°N and 30.9°N, respectively. State-of-the-art interferometers are operated at these sites within the framework of the Network for the Detection of Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). These instruments allow to record spectra on a regular basis, under clear-sky conditions, using a suite of optical filters which altogether cover the 2 to 16 micron spectral range. Numerous absorption features characterized in the HITRAN compilations (e.g. Rothman et al., 2008) are encompassed in this mid-infrared region. Their analyses with either the SFIT-1 or SFIT-2 algorithm allow retrieving total columns of the target gases. Moreover, information on their distribution with altitude can generally be derived when using SFIT-2 which implements the Optimal Estimation Method of Rodgers (1990). Among the two dozen gases of atmospheric interest accessible to the ground-based FTIR technique, we have selected here a suite of long-lived halogenated species: HCl, ClONO2, CCl2F2, CCl3F, CHClF2, CCl4 and SF6. Time series available from the two sites will be presented, compared and critically discussed. In particular, changes in the abundances of theses gases since the peak in inorganic chlorine (Cly, which occurred in 1996-1997) and their intra-annual variability will be characterized with a statistical tool using bootstrap resampling (Gardiner et al., 2008). Trends and their associated uncertainties will be reported and put into perspective with the phase-out regulations of the production of ozone depleting substances adopted and implemented by the Montreal Protocol, its Amendments and Adjustments. For instance, the trends affecting the reservoir species HCl, ClONO2, and their summation which is a good proxy of the total inorganic chlorine, have been calculated using all available daily mean measurements from January 1996 onwards. The following values were obtained for Jungfraujoch, when using 1996 as the reference year: -0.90±0.10%/yr for HCl, -0.92±0.26 %/yr for ClONO2, and -0.96±0.14 %/yr for Cly; in all cases, the uncertainties define the 95% confidence interval around the trend values. For Kitt Peak (covering 1977-2009 but with far fewer measurements than from Jungfraujoch), the corresponding trends are: -0.55±0.34 %/yr for HCl, -1.27±0.84 %/yr for ClONO2 and -0.61±0.51 %/yr for Cly, they are statistically consistent with the Jungfraujoch rates of decrease. Further trend data will be presented at the EGU General Assembly while supplementary information on Jungfraujoch results will be available from communications at the same meeting by Duchatelet et al. (2010), Lejeune et al (2010) and Rinsland et al (2010). Comparisons with model data are also foreseen. Acknowledgments The University of Liège contribution to present work has primarily been supported by the AGACC and SECPEA projects funded by the Belgian Federal Science Policy Office (BELSPO), Brussels. We further acknowledge the support of the GEOMon European project. Work at the NASA Langley Research Center was supported by NASA's Upper Atmospheric Chemistry and Modeling Program (ACMAP). References Duchatelet et al., Updating hydrogen fluoride (HF) FTIR time series above Jungfraujoch: comparison of two retrieval algorithms and impact of line shape models, this issue, 2010. Gardiner, T., A. Forbes, M. De Mazière 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. Lejeune et al., Optimized approach to retrieve information on the Tropospheric and Stratospheric Carbonyl Sulfide (OCS) vertical distributions above Jungfraujoch from high-resolution FTIR solar spectra, this issue, 2010. Rinsland et al., Long-term trend of carbon tetrachloride (CCl4) from ground-based high-resolution infrared solar spectra recorded at the Jungfraujoch, this issue, 2010. Rodgers, C.D., Characterisation and error analysis of profiles derived from remote sensing measurements, J. Geophys Res., 95, 5587-5595, 1990. Rothman, L.S., I.E. Gordon, A. Barbe et al., The HITRAN 2008 molecular spectroscopic database, J. Quant. Spectrosc. Radiat. Transfer, 110, 533-572, 2008.
    05/2010;
  • [Show abstract] [Hide abstract]
    ABSTRACT: Trends of CO2, CH4 and N2O over 1985-2010 from high-resolution FTIR solar observations at the Jungfraujoch station
    05/2010;
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper reports on daytime total vertical column abundances of formic acid (HCOOH) above the Northern mid-latitude, high altitude Jungfraujoch station (Switzerland; 46.5° N, 8.0° E, 3580 m altitude). The columns were derived from the analysis of infrared solar observations regularly performed with high spectral resolution Fourier transform spectrometers during over 1537 days between September 1985 and September 2007. The investigation was based on the spectrometric fitting of five spectral intervals, one encompassing the HCOOH ν6 band Q branch at 1105 cm−1, and four additional ones allowing to optimally account for critical temperature-sensitive or timely changing interferences by other atmospheric gases, in particular HDO, CCl2F2 and CHClF2. The main results derived from the 22 yr long database indicate that the free tropospheric burden of HCOOH above the Jungfraujoch undergoes important short-term daytime variability, diurnal and seasonal modulations, inter-annual anomalies, but no statistically significant long-term background change at the 1-sigma level. A major progress in the remote determination of the atmospheric HCOOH columns reported here has resulted from the adoption of new, improved absolute spectral line intensities for the infrared ν6 band of trans-formic acid, resulting in retrieved free tropospheric loadings being about a factor two smaller than if derived with previous spectroscopic parameters. Implications of this significant change with regard to earlier remote measurements of atmospheric formic acid and comparison with relevant Northern mid-latitude in situ findings will be assessed critically. Sparse HCOOH model predictions will also be evoked.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 01/2010; · 5.30 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The long-term trend of methane (CH4) in the lower stratosphere has been estimated for the 1985–2008 time period by combining spaceborne solar occultation measurements recorded with high spectral resolution Fourier transform spectrometers (FTSs). Volume mixing ratio (VMR) FTS measurements from the ATMOS (atmospheric trace molecule spectroscopy) FTS covering 120–10 hPa (∼16–30 km altitude) at 25°N–35°N latitude from 1985 and 1994 have been combined with Atmospheric Chemistry Experiment (ACE) SCISAT-1 FTS measurements covering the same latitude and pressure range from 2004 to 2008. The CH4 trend was estimated by referencing the VMRs to those measured for the long-lived constituent N2O to account for the dynamic history of the sampled airmasses. The combined measurement set shows that the VMR increase measured by ATMOS has been replaced by a leveling off during the ACE measurement time period. Our conclusion is consistent with both remote sensing and in situ measurements of the CH4 trend obtained over the same time span.
    Journal of Quantitative Spectroscopy and Radiative Transfer 09/2009; 110(13):1066-1071. · 2.29 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Multi-decade atmospheric OCS (carbonyl sulfide) infrared measurements have been analyzed with the goal of quantifying long-term changes and evaluating the consistency of the infrared atmospheric OCS remote-sensing measurement record. Solar-viewing grating spectrometer measurements recorded in April 1951 at the Jungfraujoch station (46.5°N latitude, 8.0°E longitude, 3.58 km altitude) show evidence for absorption by lines of the strong ν3 band of OCS at 2062 cm−1. The observation predates the earliest previously reported OCS atmosphere remote-sensing measurement by two decades. More recent infrared ground-based measurements of OCS have been obtained primarily with high-resolution solar-viewing Fourier transform spectrometers (FTSs). Long-term trends derived from this record span more than two decades and show OCS columns that have remained constant or have decreased slightly with time since the Mt. Pinatubo eruption, though retrievals assuming different versions of public spectroscopic databases have been impacted by OCS ν3 band line intensity differences of ∼10%. The lower stratospheric OCS trend has been inferred assuming spectroscopic parameters from the high-resolution transmission (HITRAN) 2004 database. Volume mixing ratio (VMR) profiles measured near 30°N latitude with high-resolution solar-viewing FTSs operating in the solar occultation mode over a 22 years time span were combined. Atmospheric Trace MOlecucle Spectroscopy (ATMOS) version 3 FTS measurements in 1985 and 1994 were used with Atmospheric Chemistry Experiment (ACE) measurements during 2004–2007. Trends were calculated by referencing the measured OCS VMRs to those of the long-lived constituent N2O to account for variations in the dynamic history of the sampled airmasses. Means and 1-sigma standard deviations of VMRs (in ppbv, or 10−9 per unit air volume) averaged over 30–100 hPa from measurements at 25–35°N latitude are 0.334±0.089 ppbv from 1985 (ATMOS Spacelab 3 measurements), 0.297±0.094 ppbv from 1994 ATLAS 3 measurements, 0.326±0.074 ppbv from ACE 2004 measurements, 0.305±0.096 ppbv from ACE 2005 measurements, 0.328±0.074 from ACE 2006 measurements, and 0.305±0.090 ppbv from ACE measurements through August 2007. Assuming these parameters, we conclude that there has been no statistically significant trend in lower stratospheric OCS over the measurement time span. We discuss past measurement sets, quantify the impact of changes in infrared spectroscopic parameters on atmospheric retrievals and trend measurements, and discuss OCS spectroscopic uncertainties of the current ν3 band parameters in public atmospheric databases.
    Journal of Quantitative Spectroscopy and Radiative Transfer 11/2008; · 2.29 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: MIPAS, the Michelson Interferometer for Passive Atmospheric Sounding, is a mid-infrared emission spectrometer which is part of the core payload of ENVISAT. It is a limb sounder, i.e. it scans across the horizon detecting atmospheric spectral radiances which are inverted to vertical temperature, trace species and cloud distributions. These data can be used for scientific investigations in various research fields including dynamics and chemistry in the altitude region between upper troposphere and lower thermosphere. The instrument is a well calibrated and characterized Fourier transform spectrometer which is able to detect many trace constituents simultaneously. The different concepts of retrieval methods are described including multi-target and two-dimensional retrievals. Operationally generated data sets consist of temperature, H2O, O3, CH4, N2O, HNO3, and NO2 profiles. Measurement errors are investigated in detail and random and systematic errors are specified. The results are validated by independent instrumentation which has been operated at ground stations or aboard balloon gondolas and aircraft. Intercomparisons of MIPAS measurements with other satellite data have been carried out, too. As a result, it has been proven that the MIPAS data are of good quality. MIPAS can be operated in different measurement modes in order to optimize the scientific output. Due to the wealth of information in the MIPAS spectra, many scientific results have already been published. They include intercomparisons of temperature distributions with ECMWF data, the derivation of the whole NOy family, the study of atmospheric processes during the Antarctic vortex split in September 2002, the determination of properties of Polar Stratospheric Clouds, the downward transport of NOx in the middle atmosphere, the stratosphere-troposphere exchange, the influence of solar variability on the middle atmosphere, and the observation of Non-LTE effects in the mesosphere.
    Atmospheric Chemistry and Physics 01/2008; 8(2008):2151-2188. · 5.51 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: MIPAS, the Michelson Interferometer for Passive Atmospheric Sounding, is a mid-infrared emission spectrometer which is part of the core payload of ENVISAT. It is a limb sounder, i.e. it scans across the horizon detecting atmospheric spectral radiances which are inverted to vertical temperature, trace species and cloud distributions. These data can be used for scientific investigations in various research fields including dynamics and chemistry in the altitude region between upper troposphere and lower thermosphere. The instrument is a well calibrated and characterized Fourier transform spectrometer which is able to detect many trace constituents simultaneously. The different concepts of retrieval methods are described including multi-target and two-dimensional retrievals. Operationally generated data sets consist of temperature, H2O, O3, CH4, N2O, HNO3, and NO2 profiles. Measurement errors are investigated in detail and random and systematic errors are specified. The results are validated by independent instrumentation which has been operated at ground stations or aboard balloon gondolas and aircraft. Intercomparisons of MIPAS measurements with other satellite data have been carried out, too. As a result, it has been proven that the MIPAS data are of good quality. MIPAS can be operated in different measurement modes in order to optimize the scientific output. Due to the wealth of information in the MIPAS spectra, many scientific results have already been published. They include intercomparisons of temperature distributions with ECMWF data, the derivation of the whole NOy family, the study of atmospheric processes during the Antarctic vortex split in September~2002, the determination of properties of Polar Stratospheric Clouds, the downward transport of NOx in the middle atmosphere, the stratosphere-troposphere exchange, the influence of solar variability on the middle atmosphere, and the observation of Non-LTE effects in the mesosphere.
    ATMOSPHERIC CHEMISTRY AND PHYSICS 01/2008; · 5.30 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report retrievals of COClF (carbonyl chlorofluoride) based on atmospheric chemistry experiment (ACE) solar occultation spectra recorded at tropical and mid-latitudes during 2004–2005. The COClF molecule is a temporary reservoir of both chlorine and fluorine and has not been measured previously by remote sensing. A maximum COClF mixing ratio of 99:7 AE 48:0 pptv (10 À12 per unit volume, 1 sigma) is measured at 28 km for tropical and subtropical occultations (latitudes below 20 in both hemispheres) with lower mixing ratios at both higher and lower altitudes. Northern hemisphere mid-latitude mixing ratios (30–501N) resulted in an average profile with a peak mixing ratio of 51:7 AE 32:1 pptv, 1 sigma, at 27 km, also decreasing above and below that altitude. We compare the measured average profiles with the one reported set of in situ lower stratospheric mid-latitude measurements from 1986 and 1987, a previous two-dimensional (2-D) model calculation for 1987 and 1993, and a 2-D-model prediction for 2004. The measured average tropical profile is in close agreement with the model prediction; the northern mid-latitude profile is also consistent, although the peak in the measured profile occurs at a higher altitude (2.5–4.5 km offset) than in the model prediction. Seasonal average 2-D-model predictions of the COClF stratospheric distribution for 2004 are also reported.
    Journal of Quantitative Spectroscopy and Radiative Transfer 07/2007; 105:467-475. · 2.29 Impact Factor
  • Scientific Assessment of Ozone Depletion: 2006, 03/2007; Global Ozone Research and Monitoring Project-Report No. 50, 572 pp., World Meteorological Organization.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Altitude profiles of ClONO<sub>2</sub> retrieved with the IMK (Institut für 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, Izaña, 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 ClONO<sub>2</sub>. 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±0.12×10<sup>14</sup> cm<sup>−2</sup> (1.0±1.1%) and −0.09±0.19×10<sup>14</sup> cm<sup>−2</sup> (−0.8±1.7%), depending on the coincidence criterion applied. χ<sup>2</sup> 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 χ<sup>2</sup> deviations. From the resulting χ<sup>2</sup> profiles there is no evidence for a systematic over/underestimation of the MIPAS random error analysis.
    Atmospheric Chemistry and Physics 01/2007; · 4.88 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: 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 (, 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 (, 3013 m altitude). The two measurement sets therefore overlap for the 1983–2004 time period. An average tropospheric volume mixing ratios of ( 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.
    Journal of Quantitative Spectroscopy and Radiative Transfer 02/2006; 97(3):457-466. · 2.29 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The first space-based measurements of upper tropospheric (110–300 hPa) formic acid (HCOOH) are reported from 0.02 cm−1 resolution Atmospheric Chemistry Experiment (ACE) Fourier transform spectrometer solar occultation measurements at 16°S–43°S latitude during late September to early October in 2004 and 2005. A maximum upper tropospheric HCOOH mixing ratio of 3.13 ± 0.02 ppbv (1 ppbv = 10−9 per unit volume), 1 sigma, at 10.5 km altitude was measured during 2004 at 29.97°S latitude and a lower maximum HCOOH mixing ratio of 2.03 ± 0.28 ppbv, at 9.5 km altitude was measured during 2005. Fire counts, back trajectories, and correlations of HCOOH mixing ratios with ACE simultaneous measurements of other fire products confirm the elevated HCOOH mixing ratios originated primarily from tropical fire emissions. A HCOOH emission factor relative to CO of 1.99 ± 1.34 g kg−1 during 2004 in upper tropospheric plumes is inferred from a comparison with lower mixing ratios measured during the same time period assuming HITRAN 2004 spectroscopic parameters.
    Geophysical Research Letters 01/2006; 33(23). · 4.46 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Volume mixing ratios (VMRs) of HF, HCl, CCl2F2, CHClF2 (HCFC-22), and SF6 in the lower stratosphere have been derived from solar occultation measurements recorded with spaceborne high resolution Fourier transform spectrometers. Atmospheric Chemistry Experiment (ACE) VMRs measured during 2004 have been compared with those obtained in 1985 and 1994 by the Atmospheric Trace MOlecule Spectroscopy (ATMOS) instrument. Trends are estimated by referencing the measured VMRs to those of the long-lived constituent N2O to account for variations in the dynamic history of the sampled air masses. Pressure-gridded measurements covering 10-100 hPa (~16 to 30 km altitude) were used in the analysis that includes typically 25°N-35°N latitude. The VMR changes provide further evidence of the impact of the emission restrictions imposed by the Montreal Protocol and its strengthening amendments and adjustments and are consistent with model predictions and known sources and sinks of halocarbons. Decreases in the lower stratospheric mixing ratios of CCl3F and HCl are measured in 2004 with respect to 1994, providing important confirmation of recent ground-based solar absorption measurements of a decline in inorganic chlorine. Trends estimates are compared with other reported measurements and model predictions.
    Geophysical Research Letters 06/2005; 32(16). · 4.46 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The average tropospheric volume mixing ratios of chlorofluorocarbon 12 (CCl2F2) have been retrieved from high-spectral resolution ground-based infrared solar-absorption spectra recorded from March 1982 to October 2003 with the McMath Fourier transform spectrometer at the US National Solar Observatory facility on Kitt Peak in southern Arizona (31.9°N, 111.6°W, 2.09 km altitude). The retrievals are based on fits to the unresolved ν8 band Q-branches near using the SFIT2 retrieval algorithm. The annual increase rate was equal to (16.88±1.37) parts per trillion (10-12) by volume at the beginning of the time series, March 1982, or (4.77±0.04)%, 1 sigma, declining progressively to (2.49±1.24) parts per trillion, by volume at the end, October 2003, or (0.46±0.24)%, 1 sigma. Average tropospheric mixing ratios from the solar spectra have been compared with average surface flask and in situ sampling measurements from the Climate Monitoring and Diagnostics Laboratory (CMDL) station at Niwot Ridge, CO, (USA) (40.0°N, 105.5°W, 3013 m altitude). The average ratio and standard deviation of the monthly means of the retrieved tropospheric mixing ratios relative to the CMDL surface mixing ratios is (1.01±0.03) for the overlapping time period. Both datasets demonstrate the progressive impact of the Montreal protocol and its strengthening amendments on the trend of CCl2F2, though a tropospheric decrease has yet to be observed.
    Journal of Quantitative Spectroscopy and Radiative Transfer 05/2005; · 2.29 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: 1] SCISAT-1, also known as the Atmospheric Chemistry Experiment (ACE), is a Canadian satellite mission for remote sensing of the Earth's atmosphere. It was launched into low Earth circular orbit (altitude 650 km, inclination 74°) on 12 Aug. 2003. The primary ACE instrument is a high spectral resolution (0.02 cm À1) Fourier Transform Spectrometer (FTS) operating from 2.2 to 13.3 mm (750– 4400 cm À1). The satellite also features a dual spectrophotometer known as MAESTRO with wavelength coverage of 285– 1030 nm and spectral resolution of 1 –2 nm. A pair of filtered CMOS detector arrays records images of the Sun at 0.525 and 1.02 mm. Working primarily in solar occultation, the satellite provides altitude profile information (typically 10– 100 km) for temperature, pressure, and the volume mixing ratios for several dozen molecules of atmospheric interest, as well as atmospheric extinction profiles over the latitudes 85°N to 85°S. This paper presents a mission overview and some of the first scientific results.
    Geophys. Res. Lett. 01/2005; 32:15-1.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The seasonal variation of the free tropospheric volume mixing ratio of formic acid (HCOOH) has been derived from high-spectral-resolution solar absorption spectra recorded with the Fourier transform spectrometer in the U.S. National Solar Observatory facility on Kitt Peak (31.9°N, 111.6°E, 2.09 km altitude) at a typical spectral resolution of 0.005 cm-1. The spectra have been analyzed with the SFIT2 algorithm, which is based on a semiempirical application of the optimal estimation method. Absorption by HCOOH is weak in these solar spectra, but successful retrievals have been obtained with a new procedure that fits the HCOOH ν6 band Q branch at 1105 cm-1 simultaneously with a window to account for a temperature-sensitive HDO line, which overlaps the HCOOH Q branch. After retaining only the best measurements from a database extending from June 1980 to October 2002 the retrievals show a seasonal variation, with a summer maximum and a winter minimum. Average 2.09-10 km volume mixing ratios binned in 3 month intervals range from a maximum of 792 ± 323 parts per trillion by volume (pptv), or 10-12, in July-September to a minimum of 313 ± 175 pptv in October-December, with the uncertainties corresponding to statistical means from daily averages. The results are compared with previously reported measurements and model calculations.
    Journal of Geophysical Research Atmospheres 09/2004; 109(D18):18308-. · 3.44 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Carbon monoxide total column amounts in the atmosphere have been measured between January 2002 and December 2003 in the High Northern Hemisphere (30°-90° N, HNH) using infrared spectrometers of high and moderate resolutions. They were compared to the mixing ratios measured in the surface layer and to the total column amounts measured by the Terra/MOPITT instrument. All the data reveal increased CO abundances in comparison with other years. Maximum anomalies (deviations from the "normal" monthly means, averaged over 2000- 2001 or over 1996 - 2001) were observed in October 2002 and August 2003. Nonetheless, these enhancements were twice as little comparing to the record high CO anomaly in October 1998. Most likely, CO emissions from the strong boreal forest fires in Russia and in Canada induced increasing CO burdens.
    AGU Spring Meeting Abstracts. 04/2004; -1:01.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Version 3 of the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment data set for some 30 trace and minor gas profiles is available. From the IR solar-absorption spectra measured during four Space Shuttle missions (in 1985, 1992, 1993, and 1994), profiles from more than 350 occultations were retrieved from the upper troposphere to the lower mesosphere. Previous results were unreliable for tropospheric retrievals, but with a new global-fitting algorithm profiles are reliably returned down to altitudes as low as 6.5 km (clouds permitting) and include notably improved retrievals of H2O, CO, and other species. Results for stratospheric water are more consistent across the ATMOS spectral filters and do not indicate a net consumption of H2 in the upper stratosphere. A new sulfuric-acid aerosol product is described. An overview of ATMOS Version 3 processing is presented with a discussion of estimated uncertainties. Differences between these Version 3 and previously reported Version 2 ATMOS results are discussed. Retrievals are available at http://atmos.jpl.nasa.gov/atmos.
    Applied Optics 12/2002; 41(33):6968-79. · 1.69 Impact Factor