Offline total ozone column

Composite offline images

NOTE: Metop-B+C image is for demonstrational purposes only, such multi-satellite product is not processed or disseminated.




Image gallery


Offline total ozone column product provides information about vertical column densities of ozone in the atmosphere. It is being produced with the latest algorithm version which is operational at the sensing time.


Offline. The product is available to users in 15 days from sensing. Typical delay is 2-3 days.

Theoretical basis

The retrieval of the product is based on GOME-2 (ir)radiance measurements in the wavelength region of 325-335 nm.


DLR generates vertical column products with Universal Processor for UV/VIS Atmospheric Spectrometers (UPAS), inside which the GOME Data Processor (GDP) operational algorithm is the baseline algorithm for the trace gas column retrievals from GOME-2.

The latest GDP 4.8/4.9 uses an optimised DOAS (Differential Optical Absorption Spectroscopy) algorithm to determine the trace gas slant column. The DOAS slant column fitting is followed by Air Mass Factor (AMF) conversions to generate vertical columns.

Units and spatial resolution

Ozone columns are given in Dobson Units (DU).

GOME-2/Metop-A has 24 forward-scan pixels with a nominal resolution of 40 km × 40 km, and 8 back-scan pixels with a nominal resolution of 120 km × 40 km.

GOME-2/Metop-B and GOME-2/Metop-C have 24 forward-scan pixels with a nominal resolution of 80 km × 40 km, and 8 back-scan pixels with a nominal resolution of 240 km × 40 km.

Both forward- and back-scan pixels are processed and written to the products.


This product is validated by LAP/AUTH. The validation is based on detailed comparisons of existing satellite data with ground-based measurements. Visit AC SAF offline total ozone column validation website for further information.

Online quality monitoring

The product quality is constantly monitored by KNMI. The online monitoring is based on near real-time validation of total ozone via data assimilation. For further information, visit website: Validation of AC SAF GOME-2 Total Ozone with data assimilation.

Archiving and dissemination

This product is archived at the DLR and available via offline data access page. Upon request, products can be directly pushed to dedicated FTP servers located at the users' premises.

File format

The product is delivered in HDF5 format, each file containing one satellite orbit (sunlit portion).

Algorithm version information

Time period GOME-2 / Metop-A GOME-2 / Metop-B GOME-2 / Metop-C
04.01.2007 – 15.07.2013 GDP 4.6 N.A. N.A.
15.07.2013 - 15.10.2016 GDP 4.7 GDP 4.7 N.A.
15.10.2016 - 16.01.2019 GDP 4.8 GDP 4.8 N.A.
16.01.2019 onwards GDP 4.8 GDP 4.8 GDP 4.9

Important algorithm changes in GDP 4.8

  • Improved retrieval algorithms and quality flags
    • O3: quality flag indexing volcanic SO2 affecting total ozone retrieval added
    • Cloud algorithm improvements (OCRA & ROCINN)


GOME-2 pages at DLR: ATMOS