Remedy 1: Improved metrological understanding of potential for MAX-DOAS high-quality measurements and retrieval techniques of tropospheric ozone

Primary gap remedy type: 
Secondary gap remedy type: 
Proposed remedy description: 

More studies are needed to investigate the potential of the MAX-DOAS remote-sensing technique for tropospheric ozone measurements. In particular, the information content (vertical sensitivity, horizontal representativeness, dependency on measurement and solar geometries, and atmospheric visibility) and uncertainty budget of those measurements must be thoroughly characterized in different spectral ranges covering both Huggins and Chappuis ozone absorption bands and for a broad range of observation geometries and atmospheric conditions. Ideally, this should be conducted in a coordinated way, e.g. as part of an instrument intercomparison experiment such as the CINDI-2 intercomparison campaign which took place in Cabauw (The Netherlands) in September 2016. More in-depth studies are also needed to investigate and characterize the different possible methods for the retrieval of tropospheric ozone from MAX-DOAS observations. With most of the active MAX-DOAS research groups involved and the creation of a dedicated MAX-DOAS Tropospheric Ozone Working Group, this campaign provides an ideal framework for these tasks, and some of these tasks are already being addressed as part of the CINDI-2 campaign effort.

Hence the recommendation is:

To provide an in-depth characterisation of the different retrieval methods and their advantages and disadvantages for the retrieval of tropospheric ozone from MAX-DOAS measurements, and to select one of them for its operational application at all MAX-DOAS sites.

To provide the corresponding retrieval results to Copernicus and Space Agencies (ESA, EUMETSAT) for validation purpose.


A better characterisation of the information content and uncertainty budget of MAX-DOAS tropospheric ozone retrievals will improve the usability of MAX-DOAS observations for model and satellite validation studies, while an improved characterisation of the MAX-DOAS tropospheric ozone retrieval is fully aligned with the requirements of providing traceable and harmonized tropospheric ozone vertical columns and profiles for satellite and model validation.

Measurable outcome of success: 

To provide MAX-DOAS tropospheric ozone retrieval results with improved information content characterization and uncertainty assessment to Copernicus and Space Agencies (ESA, EUMETSAT), and to estimate the impact of these improvements on the interpretation of model and satellite validation studies.

Expected viability for the outcome of success: 
  • Medium
Scale of work: 
  • Single institution
  • Consortium
Time bound to remedy: 
  • Less than 3 years
Indicative cost estimate (investment): 
  • Low cost (< 1 million)
Indicative cost estimate (exploitation): 
  • No
Potential actors: 
  • Copernicus funding
  • ESA, EUMETSAT or other space agency
  • Academia, individual research institutes