Abstract
Abstract. We report the ozone absolute absorption cross section between 350–470 nm, the minimum between the Huggins and Chappuis bands, where the ozone cross section is less than 10−22 cm2. Ozone spectra were acquired using an incoherent broadband cavity enhanced absorption spectrometer, with three channels centered at 365, 405, and 455 nm. The accuracy of the measured cross section is 4–30%, with the greatest uncertainty near the minimum absorption at 375–390 nm. Previous measurements vary by more than an order of magnitude in this spectral region. The measurements reported here provide much greater spectral coverage than the most recent measurements. The effect of O3 concentration and water vapor partial pressure were investigated, however there were no observable changes in the absorption spectrum most likely due to the low optical density of the complex.
Highlights
Weak spectral absorptions play an important role in the radiative transfer of the Earth’s atmosphere and accurate measurements of these are necessary for satellite retrievals of atmospheric trace gases (Burrows et al, 1999a; Bogumil et al, 2003; Petropavlovskikh et al, 2011)
Ozone concentrations were measured simultaneously with the Incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) spectral measurements using a single-pass absorption measurement at 254 nm that consisted of a 10.6 cm glass cell with quartz windows, a mercury pencil lamp (UVP 90-0012-01), and gallium phosphide (GaP) photodiode detector (Thorlabs SM05PD7A) with a 254 nm band pass filter (Fig. 1b)
The O2/O3 flow from the discharge source was diluted with He (Fig. 1b), such that only up to 3.3 % of flow through the IBBCEAS cells was from the O3 source, of which, at most 1.8 % could consist of O4
Summary
Weak spectral absorptions play an important role in the radiative transfer of the Earth’s atmosphere and accurate measurements of these are necessary for satellite retrievals of atmospheric trace gases (Burrows et al, 1999a; Bogumil et al, 2003; Petropavlovskikh et al, 2011). Previous O3 cross sections in this region have been measured using high resolution Fourier transform spectrometers (Brion et al, 1998; Voigt et al, 2001) and grating spectrometers (Burkholder and Talukdar, 1994; Burrows et al, 1999a; Bogumil et al, 2003). These studies report cross sections that differ by more than an order of magnitude near the minimum, and show some disagreement where the cross section is greater (e.g. 8 % at 350 nm and 20 % at 450 nm). These results are compared to the previous literature studies of O3 cross sections in this region
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