Total CHOCHO column data record


Total CHOCHO column data record provides long-term information about vertical column densities of glyoxal in the troposphere.


Data record

Satellites and instruments

GOME-2/Metop-A and GOME-2/Metop-B

Algorithm version

G2_L2_GLY version 1.0

Time period

  • 23/01/2007 - 31/12/2017 (GOME-2/Metop-A)
  • 01/01/2013 - 30/06/2020 (GOME-2/Metop-B)

Theoretical basis

The retrieval of the product is based on the DOAS method (Differential Optical Absorption Spectroscopy) using GOME-2 radiance measurements in the wavelength region of 405-490 nm.


The glyoxal processor is an integrated part of the AC SAF processing at DLR. First, an optimised DOAS algorithm is used to determine the glyoxal slant column. Then a daily normalization procedure based on measurements in remote Pacific Ocean is applied. In the final step, the tropospheric vertical glyoxal column is determined by Air Mass Factor (AMF) conversion, using the LIDORT RTM and a priori glyoxal profiles from the IMAGES version 3 CTM.

Units and spatial resolution

CHOCHO columns are given as vertical column densities (molecules/cm2).

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

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

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


This product has been validated by Belgian Institute for Space Aeronomy (BIRA-IASB). The validation is based on an end-to-end approach, that has been developed to evaluate independently all critical components of the level-1-to-2 retrieval chain, using correlative observations performed by ground-based and satellite instruments.

Archiving and dissemination

This product is archived at the DLR and available via data record access page.

File format

The product is delivered in NetCDF-4 format, each file containing one satellite orbit (sunlit portion).


GOME-2 pages at DLR: ATMOS