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C417: Future stratospheric ozone changes and associated surface climate impacts (Lead Supervisor: Andrew Orr, British Antarctic Survey)

Supervisors: Andrew Orr (British Antarctic Survey), Luke Abraham (Chemistry), Peter Braesicke (Karlsruhe Institute for Technology, Germany), Lars Hoffmann (Julich Research Centre, Germany) and Reinhold Spang (Julich Research Centre)

Importance of the area of research:

The Antarctic ozone hole has profound impacts on the Southern Hemisphere atmospheric circulation and surface climate. The ozone hole is caused by chemical reactions that take place primarily on the surface of polar stratospheric clouds (PSCs). With the continued implementation of the Montreal Protocol, recovery of the ozone hole is generally anticipated by the end of the century. However, model predictions using coupled chemistry-climate simulations give a large range of estimates of the rate and timing of this recovery. Accurate projections of its recovery are critical as this will further reshape Southern Hemisphere climate by no longer counteracting the effects of increasing greenhouse gases. However, the fact that the results are model dependent indicates that some mechanisms are not properly represented. In particular, to produce accurate simulations of stratospheric ozone depletion, coupled chemistry-climate models must be able to represent PSC formation mechanisms and their attendant ozone-loss chemistry due to localised dynamics such as mountain waves.

Project summary:

The aim of this project is to produce realistic projections of the recovery of the Antarctic ozone hole, and associated changes to the Southern Hemisphere atmospheric circulation and climate, by including the effects of mountain waves on PSC formation in a chemistry-climate model. Mountain waves play a crucial role in the formation of PSCs by producing localised temperature fluctuations (up to 20 K), enabling stratospheric temperatures to fall below the threshold value for PSC formation. However, small-scale mountain waves are unresolved by global chemistry-climate models, leading to insufficient PSCs. We will thus improve the representation of mountain-wave-induced PSCs in a chemistry-climate model by including a mountain wave parameterisation scheme (which computes the temperature fluctuations due to unresolved waves). The impacts of this on the Arctic climate will also be examined.

What the student will do:

Based within a strong research community at the British Antarctic Survey's headquarters in Cambridge, you will work with a version of the chemistry-climate configuration of the Unified Model (UM) numerical modelling system, which includes the simulation of mountain-wave-induced PSCs. You will evaluate and further improve the representation of PSC formation mechanisms in the model by comparison with satellite measurements, including MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) PSC observations, and mountain-wave-induced stratospheric temperature fluctuations detected by the Atmospheric Infrared Sounder (AIRS). You will use the improved model to produce more reliable future predictions of both Antarctic and Arctic stratospheric ozone, and the associated atmospheric circulation and surface climate. The project will involve considerable international collaboration with scientists at Karlsruhe Institute of Technology and Julich Research Centre, Germany, which you will visit for extended periods to work on analysis of the data.

Please contact the lead supervisor directly for further information relating to what the successful applicant will be expected to do, training to be provided, and any specific educational background requirements.

References:

Orr, A., Hosking, J. S., Hoffmann, L., Keeble, J., Dean, S. M., Roscoe, H. K., Abraham, N. L., Vosper, S., & Braesicke, P. 2015. Inclusion of mountain-wave-induced cooling for the formation of PSCs over the Antarctic Peninsula in a chemistry-climate model. Atmospheric Chemistry and Physics, vol., 15, pp. 1071-1086, DOI: 10.5194/acp-15-1071-2015.

Spang, R., and co-authors, 2012. Fast cloud parameter retrievals of MIPAS/Envisat. Atmospheric Chemistry and Physics, vol. 12, pp. 7135-7164, doi:10.5194/acp-12-7135-2012.

Thompson, D. W. J., Solomon, S., Kushner, P. J., England, M. H., Grise, K. M., & Karoly, D. J. 2011. Signatures of the Antarctic ozone hole in Southern Hemisphere surface climate change. Nature Geoscience, vol. 4, pp. 741-749.

Follow this link to find out about applying for this project.

Other projects available from the Lead Supervisor can be viewed here.

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