Reanalyzed daily IASI/Metop-C ULB-LATMOS peroxyacetyl nitrate (PAN) L2 product (total column)

The reanalyzed daily IASI/Metop-C peroxyacetyl nitrate (PAN) total column dataset (ANNI-PAN-v4R) includes the results of a flexible and robust PAN retrieval algorithm from measurements of the Infrared Atmospheric Sounding Interferometer (IASI). The method is based on the calculation of a hyperspectral range index (HRI) and subsequent conversion to PAN columns via a neural network. With this method: (1) complete temperature and humidity vertical profiles can be accounted for, (2) third‐party PAN vertical profile information can be used, (3) a full measurement uncertainty characterization is provided and (4) total column averaging kernels are provided. The ANNI-PAN-v4R IASI product builds on the heritage of the algorithm developed initially for the retrieval of ammonia (NH3), which was then adapted to the retrieval of volatile organic compounds (VOCs), including PAN ([Franco et al., 2018](https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2018JD029633)). The current version (v4) is based on the ANNI-NH3-v4 algorithm ([Clarisse et al.,2023](https://amt.copernicus.org/preprints/amt-2023-48/)), which includes several corrections to improve consistency in time and across the different IASI instruments, and introduces total column averaging kernels.
ANNI-PAN-v4R relies on ERA5 ECMWF meteorological input data ([Hersbach et al., 2020](https://rmets.onlinelibrary.wiley.com/doi/full/10.1002/qj.3803)), along with surface temperature and clouds retrieved from dedicated neural networks. A comparison of the IASI PAN product with ground-based FTIR column measurements can be found in [Mahieu et al. (2021)](https://doi.org/10.1525/elementa.2021.00027). An example of the use of the IASI PAN averaging kernels for comparison with model data is described in [Zhai et al. (2024)](https://doi.org/10.1525/elementa.2021.00027).

- Current Version: V4.0.0R, available since 2025-09-11