Paul Griffiths, Lee Murray, Alex Archibald, Vaishali Naik, Prodromos Zanis and others

Breakout session December 2nd 1500 UTC

For co-authors - What has CMIP6 added and what can we do next? Five models analysed/assessed for CMIP6 Is this enough? What can be done to increase data availability?

Ozone burdens/concentration - CMIP6 progress? Future work?

• Evaluation of ozone against observations
• More clarity on 19th century ozone levels
• Transient experiments - comparison against trends now possible
• Did we make the most/best use of TOAR-Observations - longer time series but recommendation to - use zonal means, aggregated across stations/zones.
• Further use of other types of in-situ measurements for evaluation, e.g. IAGOS? Draw on TOAR-II - Harmonisation of free-tropospheric measurements?
• Better use of satellite data, e.g. draw on TOAR-II Satellite ozone working group
• Ozone burden
• Very sensitive to tropospheric definition
• Does the WMO tropopause output work well enough for ozone burden calculations?
• O3 output available more widely than tropopause pressure (PTP)
• Back to 150ppbv (AR5) ozonopause / 125 ppbv (TOAR) definitions?
• Difficulty in comparing burden against observations (TOAR-Climate)
• Higher time frequency data?

Ozone budgets - how did CMIP6 progress? Future work?

• O3PROD and O3LOSS for AERChemMIP output
• O3PROD the sum of all the HO2/RO2 + NO reactions (as k[HO2][NO])
• O3LOSS (i) O(1D)+H2O; (ii) O3+HO2; (iii) O3+OH; (iv) O3+alkenes (isoprene, ethene,…)
• Worked well but there were some bugs in CMOR-ising/processing
• Definitely a case for saving intermediate reaction output for a short period in case of - re-processing, and for early evaluation (multi-model) of output
• Closes budget? Impacts?
• Deposition? DryNOy and DryO3 provided, as well as wetNOy but implementation/definitions - variable- capturing wet deposition accurately between models an issue
• Simpler terms possible?
• Role of stratosphere?
• Better diagnostics for quantifying Strat-to-Trop transport, or understanding role of circulation
• TOAR-II ROSTEES working group to look again at O3STE, e90 in CCMI2022, different methods for - calculating STT (stratospheric ozone, tropospheric ozone residuals)
• Improving ozone budget treatment?
• Extensive, but tractable diagnostic output required for Oy budget (Bates and Jacob) or spin/- bond processing (Evans and Edwards) would be prohibitive in long transient experiments
• Targeted experiments required - expanding beyond Ox/Oy into HOy, NOy
• Work for the TOAR-II Global and Regional Models working group?

Experimental design - future work?

• AerChemMIP deliberately focuses on SSP3-7.0 - improve collaboration with other MIPS?
• Other scenarios? Filling out the impact of policy on air quality?
• Making the scenarios more realistic and more varied
• Focusing on regional variability within scenarios, esp in the tropics
• Pulling in input from expert/interested parties in generating new scenarios, around e.g. - net-zero
• Attribution experiments - how to follow on?
• hist/histSST/piX experiments - did we capture all that we need? Do we need more?
• High time-frequency output for AQ/human health?
• Do we know what the vegetation/health communities need - connect to TOAR again here?
• Availability?
• New variants of SSPs to target specific (policy?) questions?
• Experiments aimed at assessing specific processes?
• Emissions, deposition, transport/meteorology
• Trends and/or biases?
• Earth system processes - lightning, fire, biogenic VOC
• Further experiments aimed at understanding climate penalties and benefits and the role of - emissions reductions?

What are the drivers of intermodal differences?

• Chemical scheme - do we need a chemistry-focused MIP/experiment?
• AerChemMIP and DeCK make this difficult
• What should a chemistry DeCK look like - a definite follow-up!
• O3 and CO have been a focus, what about reservoirs - H2O2, NOy etc
• Diagnostic output - are there missing/simpler diagnostics that enable models to be better - compared?
• What could be done with the current output that enable multi-model process focus (ideally - evaluation)
• Operator tendencies urgently required
• Experiments targeted on processes?
• Understanding the role of missing processes, e.g. halogens, RO2 chemistry?
• Unravelling regional biases
• The role of the stratosphere?
• Focused experiments on role of stratospheric ozone and dynamics?
• Biogenic VOCs?
• A big source of uncertainty for ERF calculations? - experiments to better understand PI ozone - and aerosols?

Breakout session TriMIPAthlon

Comments

Burdens

AF: have done 12 ensemble using WACCM - compared against Gaudel TOAR data - good regional agreement against OMI/MLS. Ensemble gives assessment of range of model data. Some regions of concern: BL/emissions influence, e.g. Tropics. Propose: assess regionally and using ensembles.

ATA: analysis of O3PRE, O3RES and intermediates required

David S: model evaluation using seasonal cycles and diurnal cycles

Mike P: separate strat from trop as they have different patterns of change - strat varies little last 20 years - can also use strat O3 for evaluation, e.g. QBO, N2O, col O3. Budgets not very satisfying - don’t compare well. AToM shows that chemistry/transport effects important. Avoid residual methods - improve diagnostics for STT

Budgets

Olivia C: output dry deposition velocities, focus on process based diagnostics for model intercomparison

KS: data request huge

LM: frequently not accurate

ATA: CCMI shows it can be done but narrow down data requirement

MP: time for some sensitivity experiments: methane and O3 feedbacks.

David S: did CMOR-ising add a burden?

Chemistry DeCK

ATA: a chemistry DeCK is (too) big. What should be priority?

KS: understanding model differences is a major undertaking, but major