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Assessment of local HOx and ROx Measurement Techniques:
Achievements, Challenges, and Future Directions

IGAC Endorsed Workshop

International HOx Workshop 2015

Organisers Andreas Hofzumahaus (Forschungszentrum Jülich, Germany) and Dwayne Heard (University of Leeds, UK)
23-25 March 2015

Measurements of HOx and ROx radicals are an important tool for the investigation of tropospheric chemistry in field campaigns and simulation chamber experiments. The measured data allow us to test chemical models simulating the atmospheric concentrations of OH, HO2 and RO2, and help to improve chemical mechanisms used in regional and global models for predictions of the atmospheric chemical composition. Even after four-decades of development and application of radical measurement techniques, accurate measurement of radical species remains a highly challenging task and requires persistent care.

From March 23-25 2015, an international, IGAC-endorsed workshop took place at JUFA, Jülich, and hosted by the Forschungszentrum Jülich, Germany, to assess the performance and reliability of current HOx measurement techniques. Fifteen international groups from Germany, UK, Ireland, France, Finland, USA, China and Japan came together to discuss achievements, challenges and future directions of techniques based on laser absorption and laser-induced fluorescence spectroscopy, chemical ionisation mass spectrometry, and chemical techniques.

The major topic for discussion was an assessment of how well we can measure OH, HO2 and RO2; how instrumental performance can be improved in terms of sensitivity, calibration and artefacts; and how the reliability of HOx and ROx measurements can be demonstrated to the international community.

As a major workshop outcome, a working group was established to guide the community in the near future in making progress on continued improvement in HOx measurements. Three goals will be pursued: the development of a common calibration unit, the development of procedures to investigate and, if necessary, eliminate possible measurement artefacts, and planning for future instrumental intercomparisons.