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Monthly gridded ozone profile climate data record (demonstrational)

Description

The monthly gridded ozone profile climate data record provides 3D ozone concentration information from the GOME-2 nadir scanning mode.

The product contains:

  • The ozone concentration on a 0.25° x 0.25° grid with 40 vertical layers in moles per layer
  • The a priori ozone concentration on a 0.25° x 0.25° grid with 40 layers in moles per layer
  • The averaging kernel, as a zonal average, in 18 bands of 10° latitude, as a 40 x 40 matrix
  • The integrated vertical (total) ozone column in moles and in Dobson units on 0.25° x 0.25° grid
  • The averaged number of spectral detector pixels used for the retrieval on 0.25° x 0.25° grid
  • The averaged number of iterations for the retrieval to converge on 0.25° x 0.25° grid
  • The averaged degrees of freedom (DFS) for the retrieval to converge on 0.25° x 0.25° grid

The DOI for this data record is 10.15770/EUM_SAF_AC_0052

Type

Cilmate data record (CDR)

Satellites and instruments

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

Algorithm version

The original level 2 ozone profile that was used to generate the gridded level 3 CDR had product algorithm version 2.10 and configuration file version 2.02.

Time period

  • GOME-2A: Jan 2007 – Nov 2021
  • GOME-2B: Jan 2013 - Dec 2024
  • GOME-2C: Jan 2019 - Dec 2024

Theoretical basis

Global Ozone Monitoring Experiment-2 (GOME-2) measures the radiance spectrum of sunlight scattered from the atmosphere in the (UV) wavelength region 260-330 nm. The absorption of ozone decreases with increasing wavelength. This differential absorption makes it possible to derive the vertical distribution of ozone in the atmosphere from the measured UV spectrum.

Processing

At KNMI, the Ozone ProfilE Retrieval Algorithm (OPERA) iteratively finds the vertical ozone profile best matching the GOME-2 reflectance using optimal estimation. The forward model is based on LidortA and uses an externally prescribed instrument response slit function. The a priori ozone climatology is (currently) based on McPeters/Labow/Logan. The surface pressure and the vertical temperature profile come from operational ECMWF forecasts. Special adaptations have been made to handle spikes in the measured radiance spectrum in the South Atlantic Anomaly.

The gridding of the level 2 profile data into level 3 is done on a 0.25° x 0.25° (lat/lon) grid with 40 layers. The averaging conserves essential information so that daily averages can be used as a basis for the monthly average without information loss.

Units and spatial resolution

The original level 2 vertical ozone profiles are retrieved as partial ozone columns in Dobson Units (DU) in 40 layers from the surface up to 0.001 hPa and are converted into moles per layer for the gridded level 3 to conform to SI and CF standards.

Validation

This product is validated by the AC SAF team (DWD (Germany) and KMI (Belgium)). The validation is based on detailed comparisons of the smoothed ozone profiles (i.e. the averaging kernel is applied) with collocated ground-based measurements (balloon soundings, lidar and microwave radiometer measurements).

The validation work has been published in AMT: Tuinder, O. N. E., Delcloo, A. W., and Achtert, P.: Quality Assessment of the AC SAF GOME-2 gridded ozone profile data records, EGUsphere, https://doi.org/10.5194/egusphere-2025-5728, 2025.

Archiving and dissemination

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

File format and size

This product is delivered in NetCDF-4 format. The size of a single monthly product file is about 1.6 GB.

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