This paper assesses the quality of IASI/Metop-A (IASI-A) and IASI/Metop-B (IASI-B) ozone (O<sub>3</sub>) products (total and partial O<sub>3</sub> columns) retrieved with the Fast Optimal Retrievals on Layers for IASI Ozone (FORLI-O<sub>3</sub>) v20151001 software for nine years (2008&ndash;2017) through an extensive inter-comparison and validation exercise using independent observations (satellite, ground-based and ozonesonde). IASI-A and IASI-B Total O<sub>3</sub> Columns (TOCs) are generally consistent, with a global mean difference less than 0.3&thinsp;% for both day- and nighttime measurements, IASI-A being slightly higher than IASI-B. A global difference less than 2.4&thinsp;% is found for the tropospheric (TROPO) O<sub>3</sub> column product (IASI-A being lower than IASI-B), which is partly due to a temporary issue related to IASI-A viewing angle in 2015. Our validation shows that IASI-A and IASI-B TOCs are consistent with GOME-2, Dobson, Brewer and SAOZ retrieved ones, with global mean differences in the range 0.1&ndash;2&thinsp;% depending on the instruments. The IASI-A and ground-based TOC comparison for the period 2008&ndash;July 2017 shows good long-term stability (negative trends within 3&thinsp;%&thinsp;decade<sup>&minus;1</sup>). The comparison results between IASI-A and IASI-B against smoothed ozonesonde partial O<sub>3</sub> columns vary in altitude and latitude, with maximum standard deviation for the 300&ndash;150&thinsp;hPa column (20&ndash;40&thinsp;%) due to strong ozone variability and <i>a priori</i> uncertainty. The worst agreement with the ozonesondes and with UV-vis retrieved TOC [satellite and ground] is found at the southern high latitudes. Compared to ozonesonde data, IASI-A and IASI-B O<sub>3</sub> products overestimate the O<sub>3</sub> abundance in the stratosphere (up to 20&thinsp;% for the 150&ndash;25&thinsp;hPa column) and underestimates the O<sub>3</sub> abundance in the troposphere (within 10&thinsp;% for the mid-latitudes and ~&thinsp;18&thinsp;% for the tropics). Based on the period 2011&ndash;2016, non-significant drift is found for the northern hemispheric tropospheric columns while a small drift prevails for the period before 2011.
Boynard, A., Hurtmans, D., Garane, K., Goutail, F., Hadji-Lazaro, J., Elissavet Koukouli, M., … Clerbaux, C. (2018). Validation of the IASI FORLI/EUMETSAT ozone products using satellite (GOME-2), ground-based (Brewer-Dobson, SAOZ, FTIR) and ozonesonde measurements. Atmospheric Measurement Techniques, 11(9), 5125–5152. https://doi.org/10.5194/amt-11-5125-2018