Near real-time IASI HNO3

Example composite images of daily distributions (day and night)


The near-real time IASI HNO3 product provides several variables from which the HNO3 profile, and corresponding averaging kernel matrix can be reconstructed/calculated.


Near real-time. Based on product requirements, the product files must be available to users within three hours after observation.

Theoretical basis

The retrieval of this product is based on the optimal estimation method. It relies on a radiative transfer model based on precalculated LUTs and an inversion scheme to process IASI level 1C radiances in near real-time.


The Fast Optimal Retrievals on Layers for IASI (FORLI) is a dedicated radiative transfer and retrieval software for IASI. It was developed at the Université Libre de Bruxelles (ULB) in collaboration with LATMOS, with the objective to provide global concentration distributions of atmospheric trace gases.

Units and spatial resolution

HNO3 profiles 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 (circular pixel 12 km in diameter) at nadir to 10 x 20 x π km2 (elliptical pixel) at larger viewing angles.


This product is validated by BIRA. Validation is based on detailed comparisons with satellite, ground-based and aircraft data. See the validation report for more details.


The product quality is constantly monitored by ULB. Internal daily reports 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 BUFR format.

Algorithm version information

FORLI v20151001_ sp20171122