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Ozone: right answer, wrong reason?

Department of Chemistry

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Prof M Evans , Dr P Edwards No more applications being accepted Competition Funded PhD Project (Students Worldwide)

About the Project

Ozone (O3) plays a central role in the Earth system: it protects the surface from harsh UV radiation, it is a pollutant, it reduces crop yields and is a climate gas. Computer models of atmospheric chemistry and transport are used to evaluate our understanding of its distribution around the world. In general, the O3 concentrations calculated by these models, agree both with themselves and with observations (1).

Despite the concentrations agreeing, the models disagree on how they reach this concentration. Some models have more chemical ozone production, some models have more transport from the stratosphere, etc. The models may be right, but for the wrong reasons. The ‘budgets’ (adding up the source and destruction terms) for O3 between the models can be quite different. The reasons for these differences are not clear, but they have existed for over 20 years (2) and little progress has been made in advancing the diagnosis of why.

If models don’t agree on the terms making up the ozone budget, our confidence in their predictions, for either the past or the future is in doubt. These differences could reflect differences in the chemical rate constants, the organic compounds considered in the models, wet deposition etc. However, without an understanding of why there are differences it is difficult to progress. The standard diagnostics of O3 production and loss have not been helpful in this understanding.

Over the last few years, some progress has been made. Edwards and Evans, (2017) (3) developed a new diagnostic for the production of ozone based on the conservation of quantum mechanical spin. This allowed for a new way of quantifying the production of ozone, which traced O3 back to the emission of organic compounds.

Similarly, Bates and Jacob (2020) (4) developed an extended Oy family within a chemistry transport model and showed it provided significant insight into new considerations for the production of ozone.

This project will continue with these methods to diagnose ozone production and loss, and apply it to a number of different atmospheric chemistry transport models.

Initial work will be done with the GEOS-Chem model, which is also the platform for the Edwards and Evans, and Bates and Jacob developments. The group in York has extensive experience of using this model to develop novel insights into the chemistry of the atmosphere. The group also has access to significant computational resources through the University of York’s Viking High-Performance Computing capability.

Initial experiments will involve diagnosing the model using both the Edwards and Evans, and the Bates and Jacob, approaches. The emphasis will then turn to developing a new diagnostic for ozone loss, based ozone production approach of Edwards and Evans. This would then provide a complete set of diagnostic tools for understanding the budget of O3 within the GEOS-Chem model.

Working with partners at the University of Rochester (Prof. Lee Murray: and the UK Met Office (Dr Fiona O’Connor: the approaches developed for GEOS-Chem will be included into two other models (GISS ModelE and UK-ESM1), and then the new budgets for O3 evaluated and compared. It will be possible to diagnose why the budgets for these models are different based on these diagnostics. This would provide more confidence in the predictions of the model both for the past and the future and help support activities in the wider CMIP activity (5).

The studentship would be based in the University of York’s, Wolfson Atmospheric Chemistry Laboratories (WACL), supervised by Prof Mat Evans ( and Dr Pete Edwards ( You would join the wider atmospheric modelling community at WACL researching a range of problems using numerical models, data analysis and machine learning. You would have the opportunity to travel to the University of Rochester and the Met-Office to learn how to run the necessary simulations for the project. Further project information:

The Leeds-York Natural Environment Research Council PANORAMA Doctoral Training partnership’s comprehensive trainer programme covers subject-specific and generic skills. Students obtain training and understanding of the full range of training topics. Students make a training plan when they start their PhD. Inductions and training on specific lab instruments and techniques will be provided by WACL. Additionally, you have access to our innovative Doctoral Training in Chemistry (iDTC): cohort-based training to support the development of scientific, transferable and employability skills.

The Department of Chemistry holds an Athena SWAN Gold Award and is committed to supporting equality and diversity for all staff and students.

Funding Notes

This project is part of the NERC Panorama Doctoral Training Programme. Appointed candidates will be fully-funded for 3.5 years. The funding includes:

Tax-free annual UKRI stipend (£15,285 full time for 2020/21)
UK tuition fees (£4,473 for 2021/22)
Research support and training charges (£7,000 in total)

International candidates (including EU) will be considered however the fee difference would need to be covered from other sources. International tuition fees for 2021 entry is £22,250.

Not all projects will be funded; a limited number of strong candidates will be appointed via a competitive process.



Candidate selection process:
You should hold or expect to achieve the equivalent of at least a UK upper second class degree in Chemistry or a related subject. Please check the entry requirements for your country:
• Applicants should submit a PhD application to the University of Leeds by 5 January 2021:
• Supervisors may contact candidates either by email, telephone or web-chat
• Supervisors rank the candidates for the assessment panel
• The assessment panel will shortlist candidates for interview from all those nominated
• The Leeds PANORAMA DTP awarding committee will award studentships following the panel interviews
• Candidates will be notified of the outcome of the panel’s decision by email
• Successful candidates will then need to submit a formal PhD application to the University of York
This PhD will formally start on 1 October 2021. Induction activities will start on 27 September.

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