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Validation of SAGE III \(O_3\) with ACE-FTS

The Stratospheric Aerosol and Gas Experiment III on the International Space Station (SAGE III/ISS) was launched on 19 February 2017 and began routine operation in June 2017. In this study, the SAGE III/ISS solar occultation ozone data have been validated using correlative satellite and ground‐based measurements such as the ACE-FTS ozone data.

The comparisons between SAGE III/ISS AO3 (aerosol ozone) and ACE‐FTS, OSIRIS, and OMPS LP are shown in the figure below. The differences between SAGE III and ACE‐FTS are in general within 5% between 15 and 45 km. Above 45 km, SAGE III shows a negative bias of ~10%. Below 15–20 km, SAGE III values become larger than ACE‐FTS by 10–20% in midlatitudes. This is consistent with an earlier study, which shows ACE‐FTS v3.5 ozone has a positive bias of ~10–20% in the upper stratosphere and mesosphere (>45 km) and negative bias of 20–30% in the UT/LS (Sheese et al., 2017).

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The mean differences and standard deviations between SAGE III/ISS AO3 and ACE‐FTS, OSIRIS, and OMPS LP are shown in the figure below. In the lower stratosphere and upper troposphere SAGE III ozone in general shows high biases against other correlative satellite measurements, with mean relative differences of ~5–10% against Aura MLS and ACE‐FTS from 20 km down to the tropopause. The differences between SAGE III and OSIRIS and OMPS LP are larger (~10–20%) in the southern hemisphere midlatitudes and in the tropics. The standard deviations of relative differences between SAGE III and other satellite measurements, except ACE‐FTS, show similar magnitudes and vertical structures. The smallest standard deviations of ~5% are found in the middle stratosphere (e.g., between 20 and 40 km). The standard deviations increase to ~10% at 50 km and ~20% at 60 km. The smaller standard deviations of differences between SAGE III and ACE‐FTS in the upper stratosphere and lower mesosphere are due to both instruments making observations during sunrise and sunset with smaller noise. Below 20 km the standard deviations also become larger. These increases result from both measurement uncertainties and mismatch (inexact coincidence) between SAGE III and other satellites.

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Reference:

Wang, H. J. R., Damadeo, R., Flittner, D., Kramarova, N., Taha, G., Davis, S., Thompson, A. M., Strahan, S., Wang, Y., Froidevaux, L., Degenstein, D., Bourassa, A., Steinbrecht, W., Walker, K. A., Querel, R., Leblanc, T., Godin‐Beekmann, S., Hurst, D., Hall, E.: Validation of SAGE III/ISS solar occultation ozone products with correlative satellite and ground based measurements, Journal of Geophysical Research: Atmospheres, 125 (11), https://doi.org/10.1029/2020JD032430, 2020.