Abstract. We present an original multi-spectrum fitting procedure to retrieve volume mixing ratio (VMR) profiles of carbonyl fluoride (COF 2 ) from ground-based high resolution Fourier transform infrared (FTIR) solar spectra. The multi-spectrum approach consists of simultaneously combining, during the retrievals, all spectra recorded consecutively during the same day and with the same resolution. Solar observations analyzed in this study with the SFIT-2 v3.91 fitting algorithm correspond to more than 2900 spectra recorded between January 2000 and December 2007 at high zenith angles, with a Fourier Transform Spectrometer operated at the high-altitude International Scientific Station of the Jungfraujoch (ISSJ, 46.5 • N latitude, 8.0 • E longitude, 3580 m altitude), Switzerland. The goal of the retrieval strategy described here is to provide information about the vertical distribution of carbonyl fluoride. The microwindows used are located in the ν 1 or in the ν 4 COF 2 infrared (IR) absorption bands. Averaging kernel and eigenvector analysis indicates that our FTIR retrieval is sensitive to COF 2 inversion between 17 and 30 km, with the major contribution to the retrieved information always coming from the measurement. Moreover, there was no significant bias between COF 2 partial columns, total columns or VMR profiles retrieved from the two bands. For each wavenumber region, a complete error budget including all identified sources has Correspondence to: P. Duchatelet (p.duchatelet@ulg.ac.be) been carefully established. In addition, comparisons of FTIR COF 2 17-30 km partial columns with KASIMA and SLIM-CAT 3-D CTMs are also presented. If we do not notice any significant bias between FTIR and SLIMCAT time series, KASIMA COF 2 17-30 km partial columns are lower of around 25%, probably due to incorrect lower boundary conditions. For each times series, linear trend estimation for the 2000-2007 time period as well as a seasonal variation study are also performed and critically discussed. For FTIR and KASIMA time series, very low COF 2 growth rates (0.4±0.2%/year and 0.3±0.2%/year, respectively) have been derived. However, the SLIMCAT data set gives a slight negative trend (−0.5±0.2%/year), probably ascribable to discontinuities in the meteorological data used by this model. We further demonstrate that all time series are able to reproduce the COF 2 seasonal cycle, which main seasonal characteristics deduced from each data set agree quite well.

Abstract. Methanol (CH 3 OH) is the second most abundant organic compound in the Earth's atmosphere after methane. In this study, we present the first long-term time series of methanol total, lower tropospheric and upper tropospheric-lower stratospheric partial columns derived from the analysis of high resolution Fourier transform infrared solar spectra recorded at the Jungfraujoch station (46.5 • N, 3580 m a.s.l.). The retrieval of methanol is very challenging due to strong absorptions of ozone in the region of the selected υ 8 band of CH 3 OH. Two wide spectral intervals have been defined and adjusted in order to maximise the information content. Methanol does not exhibit a significant trend over the 1995-2012 time period, but a strong seasonal modulation characterised by maximum values and variability in June-July, minimum columns in winter and a peak-topeak amplitude of 130 %. Analysis and comparisons with in situ measurements carried out at the Jungfraujoch and ACE-FTS (Atmospheric Chemistry Experiment-Fourier transform spectrometer) occultations have been performed. The total and lower tropospheric columns are also compared with IMAGESv2 model simulations. There is no systematic bias between the observations and IMAGESv2 but the model underestimates the peak-to-peak amplitude of the seasonal modulations.

Abstract. Methanol (CH3OH) is the second most abundant organic compound in the Earth's atmosphere after methane. In this work, we present the first long-term time series of methanol total, lower tropospheric and upper tropospheric-lower stratospheric partial columns derived from the analysis of high resolution Fourier transform infrared solar spectra recorded at the Jungfraujoch station (46.5° N, 3580 m a.s.l.). The retrieval of methanol is very challenging due to strong absorptions of ozone in the region of the selected υ8 band of CH3OH. Two wide spectral intervals have been defined and adjusted in order to maximize the information content. Methanol does not exhibit a significant trend over the 1995–2012 time period, but a strong seasonal modulation characterized by maximum values and variability in June–July, minimum columns in winter and a peak-to-peak amplitude of 130%. In situ measurements performed at the Jungfraujoch and ACE-FTS occultations give similar results for the methanol seasonal variation. The total and lower tropospheric columns are also compared with IMAGESv2 model simulations. There is no systematic bias between the observations and IMAGESv2 but the model underestimates the peak-to-peak amplitude of the seasonal modulations.

C’est au début des années 1950, bien avant qu’il ne soit question de changement climatique, que l’Université de Liège a réalisé ses premières mesures atmosphériques à la station scientifique internationale du Jungfraujoch, dans les Alpes bernoises. Ces observations pionnières ont alors notamment permis de confirmer la présence de méthane et de monoxyde de carbone dans l’atmosphère non polluée prévalant à ce site. Ravivé au milieu des années 1970 par les premières inquiétudes relatives à la destruction de l’ozone stratosphérique, le programme de surveillance n’a depuis plus cessé de fournir des données essentielles à la caractérisation de notre atmosphère et aux changements qu’elle subit sous l’influence des activités humaines ou de phénomènes naturels d’ampleur. Dans cet article, nous présentons quelques résultats déduits récemment de ce programme de longue haleine, pertinents pour la vérification de traités environnementaux internationaux.

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