Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2017-324
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
10 Apr 2017
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Diagnosing the radiative and chemical contributions to future changes in tropical column ozone with the UM-UKCA chemistry-climate model
James Keeble1, Ewa M. Bednarz1, Antara Banerjee2, N. Luke Abraham1,3, Neil R. P. Harris4, Amanda C. Maycock5, and John A. Pyle1,3 1University of Cambridge, Department of Chemistry, Cambridge, UK
2Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA
3NCAS/University of Cambridge, Department of Chemistry, Cambridge, UK
4Centre for Atmospheric Inf ormatics and Emissions Technology, Cranfield University, Cranfield, UK
5School of Earth and Environment, University of Leeds, Leeds, UK
Abstract. Chemical and dynamical drivers of trends in tropical total column ozone (TCO3) for the recent past and future periods are explored using the UM-UKCA chemistry-climate model. A transient 1960-2100 simulation is analysed which follows the representative concentration pathway 6.0 (RCP6.0) emissions scenario for the future. Tropical averaged (10° S–10° N) TCO3 values decrease from the 1970s, reaching a minimum around 2000, and return to their 1980 values around 2040, consistent with the use and emission of ozone depleting substances (ODS), and their later controls under the Montreal Protocol. However, when the ozone column is subdivided into three partial columns (PCO3) that cover the upper stratosphere (PCO3US), lower stratosphere (PCO3LS) and troposphere (PCO3T), significant differences to the behaviour of the total column are seen. Modelled PCO3T values increase from 1960–2000 before remaining steady under this particular emissions scenario throughout the 21st century. PCO3LS values decrease rapidly from 1960–2000, remain steady until around 2050, before gradually decreasing further to 2100, never recovering to their 1980s values. PCO3US values decrease from 1960–2000, before rapidly increasing throughout the 21st century, recovering to 1980s values by ~ 2020, and are significantly higher than 1980s values by 2100. Using a series of idealised UM-UKCA time-slice simulations with varying concentrations of well-mixed greenhouse gases (GHG) and ODS set to either year 2000 or 2100 levels, we examine the main processes that drive the PCO3 responses in the three regions, and assess how these processes change under different emission scenarios. Finally, we present a simple, linearised model to describe the future evolution of tropical stratospheric column ozone values based on terms representing time-dependent abundances of GHG and ODS.

Citation: Keeble, J., Bednarz, E. M., Banerjee, A., Abraham, N. L., Harris, N. R. P., Maycock, A. C., and Pyle, J. A.: Diagnosing the radiative and chemical contributions to future changes in tropical column ozone with the UM-UKCA chemistry-climate model, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-324, in review, 2017.
James Keeble et al.
James Keeble et al.
James Keeble et al.

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Short summary
In this study we explore the chemical and transport processes controlling ozone abundances in different altitude regions in the tropics for the present day, and how these processes may change under a future climate in order to determine when total column ozone values in the tropics will recover to pre-1980s values following the implementation of the Montreal Protocol and its subsequent amendments, which imposed bans on the use and emissions of CFCs.
In this study we explore the chemical and transport processes controlling ozone abundances in...
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