Production of IASI FDR and CDRs at EUMETSAT

The Infrared Atmospheric Sounding Interferometer (IASI), onboard the three Metop satellites, has been delivering critical observations for atmospheric monitoring and numerical weather prediction for almost 18 years. To further enhance the value of this long-term dataset for climate applications, EUMETSAT has undertaken a comprehensive reprocessing of the IASI data. This effort includes both Level 1 and Level 2 data, leading to the creation of a IASI Fundamental Data Record (FDR) and several Climate Data Records (CDRs).

The second release of the IASI FDR addresses and correct a known bias of approximately 0.2 K in the CO₂ band (15 µm), identified through intercomparisons with the Cross-track Infrared Sounder (CrIS) measurements. This bias was due to a suboptimal linearity correction that introduced a discontinuity in the near-real-time radiances, affecting both the temporal consistency of the record and inter-instrument consistency. The correction improves the homogeneity of the dataset and supports more accurate climate analyses. In addition, EUMETSAT has released the IASI Principal Component Scores (PCS) FDR from Metop-A and -B. Principal component compression (PCC) is applied to the IASI Level 1c radiance spectra achieving a file reduction size reduction of up to a factor of 50. Using Eigenvector files, the spectra can be reconstructed from the PCS files for downstream applications.

Several CDRs from Metop-A and Metop-B have also been produced, validated and released using algorithms developed by EUMETSAT and the Atmospheric Composition SAF (AC SAF). These include all-sky temperature and humidity profiles as well as trace gas products such as carbon monoxide (CO) and sulfur dioxide (SO₂) and ozone (O₃) CDR.

This presentation will provide an overview of the available IASI FDRs and CDRs, highlighting key validation results and application areas. It will also emphasize EUMETSAT’s efforts to ensure the continuity, consistency, and scientific integrity of satellite-based climate records, underscoring their critical role in supporting long-term climate monitoring and research.