Prof Mat Collins University of Exeter College of Engineering, Mathematics and Physical Sciences
Dr Rob Chadwick (Met Office)
Dr Hugo Lambert University of Exeter College of Engineering, Mathematics and Physical Sciences
Dr Chris Taylor Centre for Ecology and Hydrology
Location: University of Exeter, Streatham Campus, Exeter EX4 4QJ
This project is one of a number that are in competition for funding from the NERC Great Western Four+ Doctoral Training Partnership (GW4+ DTP). The GW4+ DTP consists of the Great Western Four alliance of the University of Bath, University of Bristol, Cardiff University and the University of Exeter plus five Research Organisation partners: British Antarctic Survey, British Geological Survey, Centre for Ecology and Hydrology, the Natural History Museum and Plymouth Marine Laboratory. The partnership aims to provide a broad training in earth and environmental sciences, designed to train tomorrow’s leaders in earth and environmental science. For further details about the programme please see http://nercgw4plus.ac.uk/
Students from EU countries who do not meet the residency requirements may still be eligible for a fees-only award but no stipend. Applicants who are classed as International for tuition fee purposes are not eligible for funding.
Future changes in tropical precipitation have the potential to produce some of the most severe impacts of climate change. This is particularly true in monsoon regions - over two billion people in Asia alone are dependent on monsoon rainfall. Unfortunately, current projections of regional precipitation changes in the tropics are very uncertain across models, inhibiting adaptation planning and providing major challenges for the detection and attribution of observed tropical precipitation trends.
Dynamical shifts in the location of convection have been identified as the primary driver of precipitation change in monsoon regions. However, different monsoons respond in diverse ways, with for example India generally projected to get wetter but the North American monsoon region getting drier. This suggests that the balance of processes driving rainfall change differs between the various monsoon regions. Furthermore, model biases in simulating present-day monsoons imply reduced confidence in projections.
Project Aims and Methods
In order to reduce uncertainty in projections, it is first necessary to improve our understanding of which processes are most important in each region and to quantify the role of model biases. This can lead to emergent constraints.
A new set of experiments (co-ordinated by co-supervisor Chadwick), designed to isolate the influence of different aspects of CO2 forcing on regional climate change, is included in the forthcoming set of CMIP6 (Coupled Model Intercomparison Project phase 6 experiments). These will show the balance between the effects of uniform SST warming, patterned SST warming, direct CO2 radiative absorption, the plant physiological response to CO2, and sea-ice changes, for each model and region. Changes in mean climate, seasonality, and daily-scale rainfall will all be examined. The main research questions are:
1) Which aspects of CO2 forcing are most important for driving precipitation and circulation changes in each monsoon region, both for the CMIP6 ensemble mean and inter-model uncertainty?
2) Once the dominant processes are understood, can present-day observations be used to provide emergent constraints on monsoon projections?
3) How do present-day SST biases affect CMIP6 projections of water cycle change in monsoon regions?
Usual GW4+ training plus master-level lecture courses on geophysical fluid dynamics, weather and climate, research methodology. Access to Met Office short courses on modelling, weather and climate.
Brown, J.R., Moise, A.F., Colman, R. and Zhang, H. (2016). Will a warmer world mean a wetter or drier Australian monsoon? J. Climate, 29, 4577-4596
Chadwick, R., Boutle, I. and Martin, G. (2013). Spatial Patterns of Precipitation Change in CMIP5: Why the Rich Do Not Get Richer in the Tropics. J. Climate, 26(11): 3803-3822.
Chadwick, R., Douville, H. and Skinner, C. (2017). Timeslice experiments for understanding regional climate projections: applications to the tropical hydrological cycle and European winter circulation. Clim. Dyn., DOI:10.1007/s00382-016-3488-6
Collins M, Knutti R, Arblaster J, Dufresne JL, Fichefet T, Friedlingstein P, Gao X, Gutowski WJ, Johns T, Krinner G, Shongwe M, Tebaldi C, Weaver A, Wehner M (2013) Climate change 2013: the physical science basis. Contribution of working group 1 to the fifth assessment report of the Intergovernmental Panel on Climate Change. Cambridge Univ. Press, pp 1054–1099
Li, G., Xie, S.-P., He, C. and Chen, Z. (2017). Western Pacific emergent constraint lowers projected increase in Indian summer monsoon rainfall. Nat. Clim. Change, DOI:10.1038/NCLIMATE3387
Seager R, Naik N, Vecchi GA (2010) Thermodynamic and dynamic mechanisms for large-scale changes in the hydrological cycle in response to global warming. J Clim 23(17):4651–4668
Taylor, Christopher M.; Belusic, Danijel; Guichard, Francoise; Parker, Douglas J.; Vischel, Theo; Bock, Olivier; Harris, Phil P.; Janicot, Serge; Klein, Cornelia; Panthou, Geremy (2017) Frequency of extreme Sahelian storms tripled since 1982 in satellite observations. Nature, 544 (7651). 475-478. 10.1038/nature22069
Webb M, Andrews T, Bodas-Salcedo A, Bony S, Bretherton C, Chadwick R, Chepfer H, Douville H, Good P, Kay J, Klein S, Marchand R, Medeiros B, Siebesma A, Skinner C, Stevens B, Tselioudis G, Tsushima Y, Watanabe M (2016) The Cloud Feedback Model Intercomparison Project (CFMIP) contribution to CMIP6. Geosci Model Dev. doi:10.5194/gmd-2016-70