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Introduction

In addition to the companion presentation P/2 3-13 on the seasonal cycles of conventional trace gases retrieved from ground-based FTIR spectra above Wollongong, Australia (34.45°S, 150.88°E), this contribution deepens the discussion into isotopic signals obtained from the same data set. (Due to the AGUs new copyright regulations we unfortunately could not include our conference presentation P/2 3-13, C.P. Rinsland, A. Meier, D.W.T. Griffith, and L.Chiou, "Ground-Based Measurements of Tropospheric CO, C2H6, and HCN from Australia at 34 degreesS latitude during 1997-1998," submitted to J. Geophys. Res., Dec 2000.) The retrieval of isotopic ratios from atmospheric FTIR spectra is an exciting new field.

Since 1996 high resolution ground-based infrared spectra have been recorded in solar absorption geometry at Wollongong, Australia (34.45°S, 150.88°E). Currently we operate the only NDSC (Network for the Detection of Stratospheric Change) FTIR spectrometer between 19.5°N and 45°S. We present a seasonal cycle of isotopic enrichments in stratospheric ozone, a case study on altitude resolved water vapour isotopic ratios, and first results from an isotopic study in nitrous oxide. An assessment of the current uncertainties of this new technique shows that our main limitation is given by the limited accuracy of the spectroscopic data base currently used (HITRAN96). This prevented us in particular from showing any results we obtained for CH4 and HCl originally announced for this conference.

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