XCO 2 -measurements with a tabletop FTS using solar absorption spectroscopy

Abstract. A commercial low-resolution (0.5 cm −1 ) Fourier Transform Spectrometer (FTS) has been modified and is used for determining the total column XCO 2 of the atmosphere by analysing direct solar radiation. The spectrometer has a small home-built solar tracker attached, so that it is a ready-to-use instrument. The results are validated with temporally coinciding on-site measurements taken with a high-resolution Total Carbon Column Observing Network (TCCON) FTIR spectrometer. For the whole comparison period of 5 months (26 measurement days) an agreement with TCCON results of (0.12 ± 0.08)% is achieved. This makes the spectrometer a promising candidate for a low-cost addition to the TCCON core FTIR sites, especially suitable for locations with limited infrastructure. An impressive mechanical and thermal stability is proved, enabling the spectrometer for use in field campaigns and for the monitoring of local sources.