Tropospheric ozone in global models P. Young, V. Naik, J. Brandt, R. Doherty, A. M. Fiore, C. Geels, M. I. Hegglin, L. Hu, U. Im, R. Kumar, M. Lin, A. Luhar, L. Murray, D. A. Parrish, D. Plummer, H. E. Rieder, J. Rodriguez, J. L. Schnell, M. Schultz, S. Tilmes, O. Wild, M. Woodhouse, G. Zeng, L. Zhang, J. Ziemke TOAR Chapter 7 TOAR Beijing Workshop, Jan 2016 …and thanks to all those reviewing!

Outline Chapter structure Major science points Figures Remaining issues Overlaps Request for author contributions Owen’s request

Our chapter will… Review and assess tropospheric ozone in the current generation of global chemistry models, including evaluation methods, model performance and model shortcomings.

Goals/science points Synthesize information on models Identify ways to improve model evaluation techniques and the models themselves Encourage the community* to critically reflect on the right model for the right question/purpose (and how they might assess that) *modelers, observational scientists and data analysts, and impact community

Chapter structure (currently) 1.Introduction 2.How are models evaluated? 3.How do they compare to observations? 4.Why might they be wrong? 5.Conclusions

Chapter structure (currently) 1.Introduction 2.History and description of global models and assessments 3.Methods of evaluating model performance 4.Present day ozone distribution (climatology) 5.Extreme ozone pollution episodes 6.Sub-decadal scale ozone variability 7.Long term ozone changes 8.Drivers of model biases 9.Summary and conclusions

Approach Drawing on published literature –multi-model focus, but with ref to single model studies –cut off date? No substantial new data analysis –Easier to encourage contributions –cf. WMO, IPCC

Some (key) figures

Model process schematic

Different model types…

…continued

ACCMIP vs Sofen (ann mean)

ACCMIP vs CASTNET (more in chapter)

CMIP5 vs OMI* Would like to update OMI with Free Trop TOAR Chapter 2 product *issue with this data (as is probably clear!)

Gaps & outstanding issues

Methods section Important since evaluation often ad hoc Will have more assessment of current methods (e.g. biased evaluations) Should we link to the TOAR dataset as a “gold standard”?

Extreme events Perhaps a debate to be had about using global models for this purpose Also section very US focused currently

Sub-decadal variability Needs refocusing (agree with Owen) More on (e.g.) OEI and strat variability etc Note beginnings of more ozone indices (e.g. PNA, PDO)

Long term variability/trends Keep focus on model evaluation Various papers on this to include! Beyond US, EU and remote sites, appears not much in this field? Little (no?) work on multi-decadal scale climate-ozone links

Drivers of model biases Section needs finishing Very hard (impossible?) to isolate cause of biases in complex models Will be identifying candidate processes/factors There will be unknown unknowns!

Links to other chapters (??) Chapter 1 –Could be duplication of intro material Chapter 2 –Model/obs comparisons –Pre-industrial discussion Chapter 3-6 –Applying metrics to model output?????

Author contributions… WMO is a good model (in my experience) Will be looking for volunteers on our chapter to lead of our sections (i.e. lead the writing/editing)