The tropics cover 40% of Earth’s area, include 36% of its land, and are home to 40% of its people. Africa is the continent with the largest tropical land mass, and its rapidly growing population includes many of the people who are most vulnerable to climate change. Rainfall in the tropics is dominated by the tropical rain band that encircles earth. To first order the rain-band tracks the seasonal variation in solar heating. As a result of this movement, rainfall from the tropical rain-band directly affects not only the lush tropical forests of the Congo, but regions such as the southern reaches of the Sahara. The rain-band’s movement leads to the annual West African monsoon rains on which populations in the Sahel depend, and the bi-annual rains of East Africa, which vary enormously across the region from the highlands of Ethiopia to the deserts of Somalia. Regional climate projections of rainfall in the tropics are highly uncertain and in many regions we do not know if it will get wetter or drier, posing a “grand challenge” to atmospheric science. This PhD will tackle this problem using a range of state-of-the-art global and regional models and observations to understand how climate change affects the tropical rain-belt, with a focus on Africa.
Air ascends in the tropical rain band, causing clouds and rain, and descends further north or south, causing the great deserts of the world, including the Sahara. Together these form the important large-scale pattern of circulation known as the “Hadley circulation”. Even in simple configurations of climate models without continents there is a diverse response of the tropical rain band to climate change (Stevens and Bony, 2013), which carries through to simulations of the real world (e.g. Dunning et al., 2018). This PhD will examine a range of models to generate new understanding of changes in the tropical rain band and identify the main drivers, with assessment against relevant observations to evaluate models and processes.
(1) How will climate change affect the tropical rain band, especially over Africa, and how does this depend on internal atmospheric processes, and coupled processes such as land and ocean change?
(2) How does an explicit representation of convective processes affect projected rain band changes?
(3) How do changes seen in models relate to those observed in reality, and can this be used to constrain the diverse predictions from models?
Depending on the interests of the candidate, many further objectives are possible (see website)
Leeds is 7th in the Shanghai global rankings of universities for atmospheric science. You will join a large and dynamic team at Leeds. You will work under the supervision of Dr John Marsham (Met Office joint chair at Leeds), who manages a large group working across African climate, weather, atmospheric convection and associated fields, and his past PhD students have strong records of peer-reviewed publication. Co-supervisor at the Met Office, Dr Dave Rowell, is an expert in large-scale modelling of climate change and variability in the tropics, with a particular focus on the African climate system. Co-supervisor Dr Amanda Maycock is Associate Professor with expertise in large-scale climate change and circulation. She is a member of the US CLIVAR working group on Changes to the Width of the Tropical Belt and a Lead Author for the IPCC Sixth Assessment Report.
You will be encouraged to travel to share your findings and learn from other environments, including possible fieldwork on related projects. Leeds is a founding member of the Met Office Academic Partnership, and there are also opportunities further afield. Projects such as GCRF Africa-SWIFT (https://www.ncas.ac.uk/en/swift-project
) provide opportunities to engage with researchers and practitioners across the UK and Africa.
You will have a degree in mathematical, physical or environmental science, and have some familiarity with programming. You will be interested in weather and climate. A background in meteorology is useful but not essential.
You will bring enthusiasm, the ability to learn how to use state-of-the art meteorological models and observational data, and the potential to understand some of the most pressing research questions in meteorology and climate science. A willingness to travel to Africa and other tropical regions is not essential, but may be useful.
Byrne, M.P., Pendergrass, A.G., Rapp, A.D. et al. Curr Clim Change Rep (2018) 4: 355. https://doi.org/10.1007/s40641-018-0110-5
Dunning, C.M., Black, E.C.L., Allan, R.P., (2018), Later wet seasons with more intense rainfall over Africa under future climate change, J. Clim., DOI: 10.1175/JCLI-D-18-0102.1
Schmidt, D. F., and K. M. Grise, 2017: The response of local precipitation and sea level pressure to Hadley cell expansion. Geophys. Res. Lett., 44, 10573-10582.
Stevens, B. and Bony S., What are climate models missing?, Science, 340, 1053-1054
Taylor, C.M., Belusic, D., Guichard, F., Parker, D.J., Vischel, T., Bock, O., Harris, P.P., Janicot, S., Klein, C. and Panthou, G. (2017) Frequency of extreme Sahelian storms tripled since 1982 in satellite observations. Nature544 (7651), 475-478. https://doi.org/10.1038/nature22069
Kendon E.J., R. A. Stratton, S. Tucker, J. H. Marsham, S. Berthou, D. P. Rowell and C. A. Senior, 2019: Enhanced future changes in wet and dry extremes over Africa at convection-permitting scale, Nature Comms, 10, 1794, doi: 10.1038/s41467-019-09776-9.
Wainwright et al., 2019, ‘Eastern African Paradox’ rainfall decline due to shorter not less intense Long Rains, npj Clim. Atmos. Sci., (2019) 2:34 ; https://doi.org/10.1038/s41612-019-0091-7