TOAR-II HEGIFTOM Focus Working Group


What are the differences between the vertical tropospheric ozone distributions measured by different ground-based instruments and how can we harmonize the different data sets into one?

Key objective

Evaluation and harmonization of the different free tropospheric ozone datasets of the established measuring platforms.

Major deliverable

Quality assessed ozone data sets, whereby  each measurement gets also an uncertainty and a quality flag. Thereby , representativeness and instrumental drifts will be characterized and evaluated.

Expected outcomes

  • Homogenized time series of measured tropospheric ozone with uncertainty estimates and quality flags included.
  • Traceability to a common standard for the different ground-based networks
  • Characterization and eventual correction of instrumental drifts based on cross-comparisons between instruments at sites hosting different techniques or between instruments measuring identical air masses.
  • New explorative tropospheric ozone datasets from new UV-Vis instruments (Pandora & MAX-DOAS)
  • In collaboration with other TOAR-II focus working groups: assessment of the tropospheric ozone distribution and trends of tropospheric ozone.


  • Year #01 (2021): Internal consistency within each network + preparation of Year #02
  • Year #02 (2022): Representativeness and external consistency among the networks through intercomparisons
  • Year #03 (2023): Exploitation of data sets (e.g. Trends) with other TOAR-II FWG’s & Preparation of publications


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