- Contribute to efforts to constrain future predictions of changes to the global monsoon system, which impacts billions of people
- Explore a hierarchy of climate model data and tools, from state-of-the-art models, to simpler idealised models, to pen and paper theories
- Build experience in climate dynamics, numerical modelling and experiment design, as well as skills in data analysis, coding and project management
Summer monsoons are the rainy summer seasons observed in tropical/subtropical regions around the world. As the summer hemisphere warms, tropical rain is drawn away from the Equator, particularly over land. It is estimated that over one third of the world’s population rely on monsoon rain for their water supply. Excessive rain can cause flooding with impacts on safety and hygiene, while a deficit can lead to drought and crop failure. Unfortunately future changes to the monsoons are uncertain, with different state-of-the-art models predicting both local increases and decreases in rainfall (e.g. Chadwick et al. 2013).
At the most basic level, two factors appear important in setting where monsoon rain falls: the thermal contrasts between the northern and southern hemisphere, and between land and ocean. Recently, simple energetic arguments have helped link the zonally averaged north/south location of tropical rain to the heating contrast between the hemispheres, but these arguments are less clear when applied to rain on regional scales (Atwood et al. 2020, Geen et al. 2020). This project will explore the role of east/west thermal contrasts (e.g. land-sea contrast) in setting the regional location of monsoon rain and its response to climate change. We will make use of a combination of observations, state-of-the-art model data, and idealised model simulations to explore questions such as:
- How do east/west circulations affect where rain falls locally and how it may shift in future climates? Are these regional circulation patterns constrained by the zonal-mean north/south energy balance?
- How are responses to localised, remote forcings, such as Arctic warming and aerosols, communicated between latitudes to achieve energy balance?
- Which climate change responses of the monsoons are consistent across state-of-the-art models and why?
This project would best suit a student with a numerical background, for example Physics, Maths or Meteorology, ideally with experience coding in Python or similar (e.g. Matlab, R, IDL).
HostUniversity of Birmingham
- Climate and Environmental Sustainability
Theory developed in the literature (see further reading) will be used to interpret differences between the zonal mean and regional tropical rainband response to forcings such as greenhouse gases and changes in extratropical/polar temperatures. We will use the following tools:
Isca (https://execlim.github.io/IscaWebsite/ ) is a fast idealised climate modelling framework that allows users to run simulations with different configurations of land and orography, and different levels of physical complexity. The student will run Isca to explore how theory might explain behaviour seen in observations and state-of-the-art climate models.
The 6th Phase of the Coupled Model Intercomparison Project (CMIP6) includes state-of-the-art model simulations of greenhouse gas scenarios (ScenarioMIP), as well as experiments examining physical parametrisations (CFMIP), polar amplification (PAMIP) and past climates (PMIP). This provides a large suite of data over which to explore shifts in tropical rain.
Training and skills
The student will build specialist knowledge in tropical climate dynamics, and experience in analysing and interpreting climate data and running a climate model. The student will also gain computing skills, in particular coding and visualising data with Python, with the opportunity to build further transferrable skills in model development, version control (Git) and coding in a low-level language (FORTAN). In the longer term, this PhD should provide a strong foundation for an academic career in climate dynamics research, or a career in the private sector e.g. the growing Climate Intelligence industry.
Partners and collaboration
This project is jointly supervised between the University of Birmingham and the UK Met Office. Ruth Geen (University of Birmingham) brings expertise in monsoon dynamics and in using the model hierarchy to deepen our understanding of climate. Rob Chadwick (UK Met Office) brings expertise in the tropical circulation and rainfall, their changes with climate change and variability and their representation in CMIP models. Depending on the direction taken, there may be further opportunities for collaboration with groups in the USA, China, and the University of Exeter, UK.
Student runs simple Isca simulations with various land configurations, and looks at how both the global and regional monsoon circulations respond to increased carbon dioxide, changes in prescribed ocean heat transport, and warming or cooling in the extratropics.
Student connects results to state-of-the-art CMIP6 simulations, e.g. ScenarioMIP, CFMIP, PAMIP and PMIP, and designs further idealised simulations as appropriate.
Student explores a direction of interest with further Isca simulations and CMIP6 analysis, e.g. role of cloud feedbacks, land hydrology, sea-ice, or paleo-monsoons.
Chadwick, R., Wu, P., Good, P., and Andrews, T. (2013). Asymmetries in tropical rainfall and circulation patterns in idealised CO 2 removal experiments. Climate Dyn., 40, 295–316, doi: 10.1007/s00382-012-1287-2.
Geen, R., Bordoni, S., Battisti, D. S. and Hui, K. (2020). Monsoons, ITCZs, and the Concept of the Global Monsoon, Reviews of Geophysics, 58, e2020RG000700. doi: 10.1029/2020RG000700
Atwood, A. R., Donohoe, A., Battisti, D. S., Liu, X. , and Pausata, F. S. R. (2020). Robust Longitudinally Variable Responses of the ITCZ to a Myriad of Climate Forcings, Geophys. Res. Lett., 47, e2020GL088833. doi: 10.1029/2020GL088833
Kang, S. M. (2020). Extratropical influence on the tropical rainfall distribution. Current Climate Change Reports, 6, 24–36. doi: 10.1007/s40641-020-00154-y
Adam, O., Bischoff, T., & Schneider, T. (2016a). Seasonal and interannual variations of the energy flux equator and ITCZ. Part I: Zonally averaged ITCZ position. Journal of Climate, 29(9), 3219–3230. https://doi.org/10.1175/JCLI‐D‐15‐0512.1
Adam, O., Bischoff, T., & Schneider, T. (2016b). Seasonal and interannual variations of the energy flux equator and ITCZ. Part II: Zonally varying shifts of the ITCZ. Journal of Climate, 29(20) 7281-7293. doi: 10.1175/JCLI‐D‐15‐0710.1
Boos, W. R., & Korty, R. L. (2016). Regional energy budget control of the Intertropical Convergence Zone and application to mid‐Holocene rainfall. Nature Geoscience, 9(12), 892–897. doi: 10.1038/ngeo2833
This project will be computational, using infrastructure at the University of Birmingham which has remained available throughout the COVID-19 pandemic. All goals would be achievable while working remotely. The student will be supported in engaging with the local, national and international scientific communities virtually if COVID-19 limits opportunities for travel and networking.