Daily IASI/Metop-A ULB-LATMOS carbon monoxide (CO) L2 product (total column)

The daily IASI/Metop-A carbon monoxide (CO) dataset is processed 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). The IASI CO retrievals are performed in the 2143-2181.25 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 25 % are processed. The FORLI-CO product is a vertical profile given as partial columns in molecules per square centimeter in 18 layers between the surface and 18 km, with an extra layer from 18 km to the top of the atmosphere. This IASI CO dataset, including CO total columns, are provided on the global scale from October 2007 till present. It also includes other relevant information such as quality flags, the a priori profile, the total error profile and the averaging kernel (AK) matrix, on the same vertical grid. The CO vertical profiles will be made available soon in a different updated dataset.

Versions of FORLI used for the processing of this dataset:
- FORLI v20100825: 1rst October 2007 – 29 September 2014
- FORLI v20140922: from 30 September 2014 till present

The FORLI software has also been set-up to retrieve ozone (O₃) vertical profiles. The daily IASI/Metop-A O₃ dataset is also available on the AERIS website [O3_IASI_A](https://en.aeris-data.fr/metadata/?09f3843e-eec0-42b0-8c87-30c91f4b3e4a).

Disclaimer: The Eumetsat IASI PPF L2 data processing chain has been updated several times since IASI launch, which can induce discontinuities in the retrieved CO time-series.