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See detailValidation of ACE-FTS measurements of CFC-11, CFC-12 and HCFC-22 using ground-based FTIRs
Kolonjari, F; Walker, K A; Mahieu, Emmanuel ULg et al

Poster (2013, December 10)

Satellite data can be an effective global monitoring tool for long-lived compounds in the atmosphere. The Atmospheric Chemistry Experiment (ACE) is a mission onboard the Canadian satellite SCISAT. The ... [more ▼]

Satellite data can be an effective global monitoring tool for long-lived compounds in the atmosphere. The Atmospheric Chemistry Experiment (ACE) is a mission onboard the Canadian satellite SCISAT. The primary instrument on SCISAT is a high-resolution infrared Fourier transform spectrometer (ACE-FTS) which is capable of measuring a range of gases including key chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) species. These families of species are of interest because of their significant contribution to anthropogenic ozone depletion and to global warming. To assess the quality of data derived from satellite measurements, validation using other data sources is critical. Ground-based Fourier transform infrared spectrometers (FTIRs) are particularly useful for this purpose. In this study, five FTIRs located at four sites around the world are used to validate the CFC-11 (CCl3F), CFC-12 (CCl2F2), and HCFC-22 (CHClF2) retrieved profiles from ACE-FTS measurements. These species are related because HCFC-22 was the primary replacement for CFC-11 and CFC-12 in refrigerant and propellant applications. The FTIRs used in this study record solar absorption spectra at Eureka (Canada), Jungfraujoch (Switzerland), Poker Flat (USA), and Toronto (Canada). The retrieval of CFC-11, CFC-12, and HCFC-22 are not standard products for many of these FTIRs, and as such, a harmonization of retrieval parameters between the sites has been conducted. The retrievals of these species from the FTIR spectra are sensitive from the surface to approximately 20 km, while the ACE-FTS profiles extend from 6 to 30 km. For each site, partial column comparisons between coincident measurements of the three species and a validation of the observed trends will be discussed. [less ▲]

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See detailValidation of ACE-FTS using ground-based FTIR measurements of CFC-11, CFC-12 and HCFC-22
Kolonjari, F.; Mahieu, Emmanuel ULg; Walker, K.A. et al

Poster (2012, July 24)

Satellite data can be an effective global monitoring tool for long-lived compounds in the atmosphere. The Atmospheric Chemistry Experiment (ACE) is a mission on-board the Canadian satellite SCISAT. The ... [more ▼]

Satellite data can be an effective global monitoring tool for long-lived compounds in the atmosphere. The Atmospheric Chemistry Experiment (ACE) is a mission on-board the Canadian satellite SCISAT. The primary instrument on SCISAT is a high-resolution infrared Fourier Transform Spectrometer (ACE-FTS) which is capable of measuring a wide range of gases including key chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) species. These families of species are of interest because of their significant contribution to anthropogenic ozone depletion and to global warming. To assess the quality of data derived from satellite measurements, validation using other data sources is critical. Ground-based Fourier transform infrared spectrometers (FTIRs) are particularly useful for this purpose. In this study, five FTIRs located at four sites around the world are used to validate the CFC- 11, CFC-12, and HCFC-22 data products from ACE-FTS. These species are related; HCFC-22 was the primary replacement for CFC-11 and CFC-12 in refrigerant and propellant applications. The five FTIR instruments used in this study record solar absorption spectra at Eureka, Canada, Jungfraujoch, Switzerland, Poker Flat, USA, and Toronto, Canada. Details on the instrumentation at each site will be provided. The retrieval of CFC-11, CFC-12, and HCFC-22 are not standard products for many of these FTIRs, and as such, the initial stage of this study is to develop the retrieval of each species. Harmonization of retrieval parameters between the sites is an important step in this process. The development of these retrievals and preliminary results will be presented. Additionally, a new method for the validation of ACE-FTS measurements will be discussed. [less ▲]

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See detailObserved and simulated time evolution of HCl, ClONO2, and HF total column abundances
Kohlhepp, R; Ruhnke, R; Chipperfield, M P et al

in Atmospheric Chemistry and Physics (2012), 12(7), 3527--3556

Time series of total column abundances of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) were determined from ground-based Fourier transform infrared (FTIR) spectra ... [more ▼]

Time series of total column abundances of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) were determined from ground-based Fourier transform infrared (FTIR) spectra recorded at 17 sites belonging to the Network for the Detection of Atmospheric Composition Change (NDACC) and located between 80.05°N and 77.82°S. By providing such a near-global overview on ground-based measurements of the two major stratospheric chlorine reservoir species, HCl and ClONO2, the present study is able to confirm the decrease of the atmospheric inorganic chlorine abundance during the last few years. This decrease is expected following the 1987 Montreal Protocol and its amendments and adjustments, where restrictions and a subsequent phase-out of the prominent anthropogenic chlorine source gases (solvents, chlorofluorocarbons) were agreed upon to enable a stabilisation and recovery of the stratospheric ozone layer. The atmospheric fluorine content is expected to be influenced by the Montreal Protocol, too, because most of the banned anthropogenic gases also represent important fluorine sources. But many of the substitutes to the banned gases also contain fluorine so that the HF total column abundance is expected to have continued to increase during the last few years. The measurements are compared with calculations from five different models: the two-dimensional Bremen model, the two chemistry-transport models KASIMA and SLIMCAT, and the two chemistry-climate models EMAC and SOCOL. Thereby, the ability of the models to reproduce the absolute total column amounts, the seasonal cycles, and the temporal evolution found in the FTIR measurements is investigated and inter-compared. This is especially interesting because the models have different architectures. The overall agreement between the measurements and models for the total column abundances and the seasonal cycles is good. Linear trends of HCl, ClONO2, and HF are calculated from both measurement and model time series data, with a focus on the time range 2000–2009. This period is chosen because from most of the measurement sites taking part in this study, data are available during these years. The precision of the trends is estimated with the bootstrap resampling method. The sensitivity of the trend results with respect to the fitting function, the time of year chosen and time series length is investigated, as well as a bias due to the irregular sampling of the measurements. The measurements and model results investigated here agree qualitatively on a decrease of the chlorine species by around 1%yr-1. The models simulate an increase of HF of around 1%yr-1. This also agrees well with most of the measurements, but some of the FTIR series in the Northern Hemisphere show a stabilisation or even a decrease in the last few years. In general, for all three gases, the measured trends vary more strongly with latitude and hemisphere than the modelled trends. Relative to the FTIR measurements, the models tend to underestimate the decreasing chlorine trends and to overestimate the fluorine increase in the Northern Hemisphere. At most sites, the models simulate a stronger decrease of ClONO2 than of HCl. In the FTIR measurements, this difference between the trends of HCl and ClONO2 depends strongly on latitude, especially in the Northern Hemisphere. [less ▲]

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