Implementing a Globally Coordinated Change in Ozone Cross-Section Value for Surface Ozone Monitoring

The reference method for ground-level ozone measurements is based on UV photometry, with replicates of the NIST Standard Reference Photometer (SRP) acting as primary standards for numerous national and international ozone-monitoring networks. Therefore measurements of ozone amount fractions in ambient air are ultimately anchored to the value of the ozone absorption cross-section at the wavelength 253.65 nm. A consensus value with the smallest uncertainty ever achieved was published in 2019*. Global coordination is now required to implement the 2019 value, which will increase the measured atmospheric ozone concentrations. The workshop aimed to gather representatives of reference laboratories, monitoring networks, legislators, and ozone analyser manufacturers to develop a plan and timetable for the adoption of the 2019 value.

The virtual workshop included five on-line sessions from Monday 5 to Friday 9 October 2020: see the full agenda .

Each session started at 12:00 (UTC+2)

• Monday: Surface ozone measurement and its impact / Survey feedback
• Tuesday: International standards, calibration services and monitoring networks
• Wednesday: Air quality normative aspects; ozone analyser manufacturing
• Thursday: Break out session for Task Groups
• Friday: Feedback from Task Groups, conclusions and recommendations

5-9 October 2020	online
Steering Committee: P. Brewer NPL R.I. Wielgosz BIPM S. Lee KRISS I. Chubchenko VNIIM J. Carney NIST J.T. Hodges NIST J. Norris NIST K. Saarnio FMI N. Ntsasa NMISA A. Borowiak JRC Workshop Executive Secretary: J. Viallon (BIPM) Agenda Presentations

Following stakeholder consultation during the Workshop, the CCQM Gas Analysis Working Group is issuing a statement on its intention to change the Ozone Cross-Section Value used for Surface Ozone Standards and Measurement.