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Titre du document / Document title

Continuous observations of atmospheric trace gases by ground-based FTIR spectroscopy at Izaña Observatory, Tenerife Island

Auteur(s) / Author(s)

SCHNEIDER Matthias ;

Résumé / Abstract

Worldwide stratospheric ozone decline is observed with great concern, since it yields an increase of the harmful UV radiation on the Earth surface and it may contribute to climate change. While in the past, it was focusedon the investigation of the polar atmosphere, there is now a growing interest in lower latitudes, where stratospheric O3 is mainly produced and measurement data are still sparse. Therefore, a Fourier spectrometer manufactured by Bruker was installed at the subtropical site of the Izaña Observatory (28°N, 2367 m a.s.l.) on Tenerife, Spain, in February 1999, with the objective to perform long-term measurements. Between February 1999 and July 2001 measurements on approximately 200 days were conducted and analyzed within this work. The height dependent pressure broadening allows to invert trace gas profiles by the measured solar absorption spectra. The inversion was performed using the Tikhonov-Phillips method on a logarithmic scale. The retrieved profiles and column amounts showed typical annual cycles with enhanced upwelling in summer, due to a stratosphere with strong tropical characteristics, and relatively high variability in winter, caused by horizontal transport as a result of enhanced wave activity. We found a good agreement between the column amounts determined by the Fourier spectrometer and those obtained by Differential Optical Absorption Spectroscopy, the Brewer spectrometer, O3 sondes, radiosondes, and measurements conducted simultaneously by another Fourier spectrometer close to Izaña. We also compared O3 sonde profiles and O3 profiles obtained by the Fourier spectrometer, which coincided on 45 days, and found good agreement. H2O profiles detected by the radiosonde coincided on 152 days with the Fourier spectrometer measurements. The corresponding profiles agree well between 4 and 20 km. Data of a three dimensional Chemical Transport Model were available for nearly the whole measurement period. These data show a similar annual evolution, however, some significant differences from the Fourier spectrometer results are found. All these differences can be explained by the modelled stratosphere with a stronger coupling to the tropics than detected in the measurements. The short-term variability of the trace gases can be attributed mainly to transport processes. This was shown by trace gas ratios which show less short-term variability than the respective trace gas column amounts themselves. Further investigation of the trace gas variations was made with meteorological parameters, like tropopause height and backward trajectories. A correlation was derived between the tropopause height and the trace gas profiles, which confirms the role of vertical transport in short-term variability. The importance of horizontal transport in this respect was demonstrated by a correlation between the origin of the airmasses and the trace gas profiles. While the model shows no correlation with the tropopause height, it demonstrates a similar correlation with the origin of the airmass. The former may be attributed to a boundary effect, since the lowest model layer (10 km) is in the typical tropopause region. The latter demonstrates that the model calculates a latitudinal trace gas variation similar to that detected by the Fourier spectrometer.

Revue / Journal Title

Wissenschaftliche Berichte FZKA    ISSN  0947-8620 

Source / Source

2002, vol. 6727, pp. A-156

Langue / Language

Anglais
Revue : Allemand

Editeur / Publisher

Forschungszentrum Karlsruhe, Karlsruhe, ALLEMAGNE  (1995) (Revue)

Localisation / Location

INIST-CNRS, Cote INIST : 16334 B, 35400010106467.0010

Nº notice refdoc (ud4) : 13640901



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