Daily IASI NH3 total column (demonstrational)

Example composite images of daily distributions (day and night)

Image gallery


The daily IASI NH3 product from Metop-B and Metop-C provides NH3 total columns with associated retrieval errors. A flag summarizes the quality of each observation: 2 for the most reliable pixels ("stringent quality assurance" in the ATBD definition), 1 for the valuable pixels, to use with caution ("weak quality assurance" in the ATBD definition) and 0 for the remaining pixels with no quality assurance. The ATBD gives the algorithm for constructing this flag. In addition to time indications and geographic coordinates, orbit, scan and pixel numbers are used to identify data, and a flag allows you to identify day and night data.


Daily. The product files are available to users every day.

Theoretical basis

The retrieval of this product is based on two steps: the calculation for each IASI observation of a hyperspectral range index (HRI) and the conversion of the HRI into a total column abundance via an artificial feedforward neural network.


The IASI NH3 product is produced within the ANNI (artificial neural network for IASI) retrieval framework. ANNI has been developed at the Université Libre de Bruxelles (ULB) in collaboration with LATMOS, to perform global retrievals of NH3. The IASI NH3 retrieval relies on meteorological information directly obtained from the IASI measurements.

Units and spatial resolution

NH3 total columns are given in moles/cm2. In 8 seconds a total of 120 views are collected over a swath of ∼2200 km, divided as 30 arrays of four individual pixels varying in size from 36 x π km2 at nadir (circular pixel 12 km in diameter) to 10 x 20 x π km2 at larger viewing angles (elliptical pixel).


IASI NH3 measurements have been compared with ground-based and airborne independent observations in Van Damme et al., 2015 and Dammers et al., 2016. A dedicated validation study was performed, and a good correlation was found between in-situ vertical profiles and IASI NH3 total columns in Guo et al., 2021 (doi: 10.1029/2020JD033475.


The product is currently running at ULB. As soon as the product will be implemented at EUMETSAT, internal daily reports will assess the daily match between the offline local product and the operational EUMETSAT product.


See NRT access information.

File format

This product is available in NetCDF format.

Algorithm version information

ANNI v3.1