The Level-2 Aura Ozone Monitoring Instrument (OMI) Nitrogen Dioxide (NO2) Slant Column Product (OMNO2A) version 4 is now available from NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) for public access. The data are produced at a spatial resolution of 13x24 km2. The shortname for this Level-2 NO2 Product is OMNO2A_V004. The data was re-processed in December 2022 using collection 4 Level 1b data and the OMNO2A processor version 4.0.0. Since then, this version of the product is also being produced in the forward stream. This version of the product was publicly released in March 2026.
The KNMI OMI NO2 processing chain consists of two steps. First, retrieval of the NO2 Slant Columns using the Differential Absorption Spectroscopy (DOAS) fitting technique. This step is done at NASA and produces the OMNO2A product. Second, computation of the NO2 Total and Tropospheric Column using data assimilation which will be done by KNMI. The resulting product of the second step is the OMNO2B product. Before collection 4, this product was called TM5-MP-DOMINO. The OMNO2A product contains slant column densities and related information, such as the wavelength calibration parameters, as well as additional information, notably geolocation and viewing data and external imput data (such as surface and cloud data). Note that the OMNO2A and OMNO2B product share the same product format. For this reason, several fields in the OMNO2A product only contain fill values. The lead scientist for this product is Dr. J. van Geffen.
The OMNO2A files are stored in NetCDF 4 format. Each file contains data from the day lit portion of an orbit (~53 minutes). There are approximately 14 orbits per day. The maximum file size for the OMNO2A data product is about 15 Mbytes.