O3 responses in CMIP6 AerChemMIP experiments: different roles of O3 precursors, CH4 concentrations and climate change
- 1School of GeoSciences, The University of Edinburgh, UK (Zhenze.Liu@ed.ac.uk)
- 2Lancaster Environment Centre, Lancaster University, UK
- 3Met Office Hadley Centre, UK
A new version of the UKCA chemistry-climate model with highly reactive volatile organic compounds (VOCs) is used to investigate the ozone (O3) responses in historical (2004-2014) and future (2045-2055) shared socio-economic pathways (SSPs) scenarios of CMIP6 AerChemMIP experiments. Significant increases in surface O3 levels in South and East Asia are simulated in the new version compared with the standard UKCA model. The O3 production and the O3 burden averaged over the troposphere increase slightly by 6 % as a result of more highly reactive VOCs, but the O3 lifetime is quite similar. Comparing the different SSP scenarios using this new model version we find the averaged surface O3 concentrations are higher in the scenario with high emissions than for historical conditions. O3 concentrations are much lower than historical O3 concentrations when O3 precursor concentrations are low. However, regional O3 increases occur in East Asia in the future scenario with low emissions of short-lived climate forcers due to strong VOC limited regimes. Decreases in surface O3 concentrations occur globally in the future scenario that has lower methane (CH4) concentrations. We construct O3 and O3 production isopleths. These both suggest that the threshold of NOx/VOCs shifting from NOx limited to VOC limited regimes is approximately 0.8. More areas become VOC limited in South Asia in all future scenarios, but there is little change for East Asia. The hydroxyl radical (OH) concentrations generally increase in regions with high O3 precursor abundances in the future scenario, but the high OH levels are offset by lower CH4 concentrations in the future low CH4 scenario. We find that there are small changes in O3 production efficiency in continental regions in all future scenarios. Relative O3 burden changes between the future SSP and historical scenarios are larger in the troposphere than in the planetary boundary layer (PBL), illustrating that O3 burdens are less sensitive in the PBL under emission and climate change. The O3 lifetime in the troposphere decreases in all future scenarios as compared to the historical period. We find that the decreases in O3 precursors and CH4 concentrations play important roles in reducing O3 burdens in the future.
How to cite: Liu, Z., M. Doherty, R., Wild, O., M. O’Connor, F., and T. Turnock, S.: O3 responses in CMIP6 AerChemMIP experiments: different roles of O3 precursors, CH4 concentrations and climate change, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15685, https://doi.org/10.5194/egusphere-egu21-15685, 2021.
