Project highlights

  • 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 the state-of-the-art models that provide the projections used by the Intergovernmental Panel on Climate Change, 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. Extremes in monsoon rain and damage caused by tropical cyclones make headlines year on year, and such events are expected to become more common under climate change. However, changes in even climatological monsoon precipitation remain highly uncertain, with different state-of-the-art models predicting both local increases and decreases in rainfall (e.g. Chadwick et al. 2013). With over one third of the world’s population relying on monsoon rain for their water supply, it is critical to better understand the controls on monsoon systems. 

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? 
  • How does the large-scale circulation interact with shorter-lived weather systems, particularly those driving rainfall extremes? 

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). 

Maps show where monsoon rain falls in June-Sept and Dec-March and photos show dry vs vegetated mountains in May vs August.

Figure 1: Tropical rain shifts north and south into the summer hemisphere throughout the year, particularly over land, accompanied by changes in the prevailing low-level wind direction. Top: Maps of precipitation and lower-level winds in boreal summer and winter. Bottom: Photos of Western Ghats, India, in 2010: (left) May, before the monsoon arrives vs (right) August, during the monsoon (Arne Hückelheim). 

CENTA Flagship

This is a CENTA Flagship Project

Case funding

This project is suitable for CASE funding


University of Birmingham


  • Climate and Environmental Sustainability


Project investigator

Dr. Ruth Geen, University of Birmingham, [email protected]


Dr. Robin Chadwick, UK Met Office, [email protected]

How to apply


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 ( ) 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

Students will be awarded CENTA2 Training Credits (CTCs) for participation in CENTA2-provided and ‘free choice’ external training. One CTC equates to 1⁄2 day session and students must accrue 100 CTCs across the three years of their PhD.  

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, and includes a CASE studentship with 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, India, and the University of Exeter, UK. 

Further details

Further details on how to contact the supervisor for this project and how to apply for this project can be found here: 

For any enquiries related to this project please contact Dr. Ruth Geen, [email protected]. 

To apply to this project: 

  • You must include a CENTA studentship application form, downloadable from: CENTA Studentship Application Form 2024. 
  • You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities. 
  • Please submit your application and complete the host institution application process via: Please select the PhD Geography and Environmental Science (CENTA) 2024/25 Apply Now button. The CENTA application form 2024 and CV can be uploaded to the Application Information section of the online form.  Please quote CENTA 2024-B15  when completing the application form. 

Applications must be submitted by 23:59 GMT on Wednesday 10th January 2024. 

Possible timeline

Year 1

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.

Year 2

Student connects results to state-of-the-art CMIP6 simulations, e.g. ScenarioMIP, CFMIP, PAMIP and PMIP, and designs further idealised simulations as appropriate.

Year 3

Student explores a direction of interest with further Isca simulations and CMIP6 analysis, e.g. role of cloud feedbacks, land hydrology, sea-ice, interactions with rainfall extremes.

Further reading

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.‐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 

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 

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 

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 

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 

Nicknish, P. A., Chiang, J. C. H., Hu, A. and Boos, W. R. (2023) Regional tropical rainfall shifts under global warming: an energetic perspective. Environ. Res.: Climate 2 015007. doi: 10.1088/2752-5295/acb9b0