Multi-spectral investigation of ozone: Part I. Setup & uncertainty budget

Abstract

This is the first in a series of two papers concerned with new accurate high resolution spectroscopic measurements of line positions and intensities of ozone in the 5 µm and 10 µm regions using a commercial Michelson Fourier transform spectrometer. Measurements in both wavelength regions have been made quasi simultaneously using a special H-shaped absorption cell with two parallel absorption paths of different lengths that remained connected during the experiments. Accurate ozone partial pressures were monitored on the shorter of the two paths using UV absorption at the 253.65 nm Hg reference line. In this paper, we report in detail on the experimental setup and provide a comprehensive uncertainty analysis. The spectral analysis and retrieved line parameters are provided in the second paper, which also contains the comparison to the literature data. Line positions have been measured with standard uncertainties of u(ν0)=3·10−5 cm-1 in both spectral regions, mainly in the ν3 and the ν1+ν3 bands of ozone. Intensities of most of the transitions in the ν3 band have a relative standard uncertainty of ur(S)=1.1·10−2. The uncertainty is slightly smaller for intensities in the ν1+ν3 band at 5 µm. The highly accurate experimental data provide a benchmark for molecular calculations and the 1.1 % line intensity uncertainty will help resolving the discrepancy between UV and IR atmospheric ozone retrievals and correcting current biases in spectroscopic databases.