Daily IASI/Metop-B ULB-LATMOS ozone (O3) L2 product (vertical profile and columns – AC SAF/EUMETSAT processing)

The daily IASI/Metop-B ozone (O₃) dataset is processed by EUMETSAT Application Ground Segment using the Fast Optimal Retrievals on Layers for IASI (FORLI) software [(Hurtmans et al., 2012)](https://doi.org/10.1016/j.jqsrt.2012.02.036) in the [AC SAF](https://acsaf.org/) framework. The IASI O₃ retrievals are performed in the 1025-1075 cm^-1 spectral range using the optimal estimation method and tabulated absorption cross sections at various pressures and temperatures to speed up the radiative transfer calculation. A single a priori is used in the retrieval scheme. The temperature, pressure, humidity profiles and cloud fractions used in FORLI are those from the EUMETSAT Level 2 processor. Only pixels associated with cloud fraction below 13 % are processed. The IASI O₃ product is a vertical profile given as partial columns in moles per square meter in 40 layers between the surface and 40 km, with an extra layer from 40 km to the top of the atmosphere. The dataset consists in 2 files per day of observation:

- a file containing the total, tropospheric and 0-6km partial columns along with their total error associated.
- a file containing the retrieved profile, the pressure levels associated with retrieval layers, and other relevant information such as a general quality flag, the a priori profile, the total error profile, the air partial column profile, and the averaging kernel (AK) matrix, on the same vertical grid. Total or partial columns can be directly calculated from the retrieved vertical profile by summing ozone partial columns on the ad hoc layers.

The dataset consists of two consistent records, processed using the same version of the EUMETSAT Level 2 processor and FORLI software (FORLI v20151001):

- Climate Data Record (CDR): available from February 2013 to December 2023. The CDR product, which provides stable, high-quality data for climate studies is built from the EUMETSAT IASI O₃ Climate Data Record Release 1, processed with Version 6.5 of the processor (DOI: 10.15770/EUM_SAF_AC_0051).
- Interim Climate Data Record (ICDR): available from January 2024 to present. The ICDR product includes more recent data with a 1-day latency, enabling near-real-time climate monitoring. It is built from the EUMETSAT near-real-time Level 2 O₃ product, processed with Version 6.7 of the processor.

Note: The two EUMETSAT version numbers (6.5 and 6.7) have no impact on the O₃ data retrievals, therefore both records can be used together.

Disclaimers: The ICDR data file of day D can still be updated until day D+30 because of some potential missing data.