Dynamics Controlling the Seasonal Cycle of Congo Basin Evaporation
David is a DPhil student in the Climate Research Lab at the School of Geography and the Environment, University of Oxford. His doctoral research focuses on improving scientific understanding about the seasonal cycle of Congo Basin evaporation. He holds an MSc in Applied Meteorology (Distinction) from the University of Reading, where he specialised in climate change, tropical meteorology and environmental data analysis. He also holds a BA in Geography (First Class) from the University of Oxford, where he specialised in physical geography and climate variability.
Alongside his doctoral research, David is a Meteorological Observer at the Radcliffe Meteorological Station, which holds the longest single-site set of temperature and rainfall records in the United Kingdom. He undertook a nine-week work placement at the Centre for Ecology and Hydrology in Wallingford in 2019, funded by Hydro-JULES. Working within the team responsible for the COSMOS-UK environmental monitoring network, he wrote the code underpinning a new actual evaporation (AET) data system, which is now deriving AET in near real time for 50 COSMOS-UK sites around the UK as a residual of the surface energy balance. He also undertook a twelve-week work placement at the Met Office in Exeter in 2017. Working in the OSTIA sea surface temperature analysis group, he set up a night-time only configuration of the OSTIA system, and evaluated the benefits of this system compared to the existing one in a technical report.
Awards and Funding
- 2016-2021: Natural Environment Research Council (NERC) DTP Studentship
- 2015: Postgraduate Scholarship, MSc in Applied Meteorology
- 2015: Gibbs Prize for the best performance, BA in Geography
- 2015: H.O. Beckitt Prize for the best physical geography dissertation, BA in Geography
- 2013: Academic Scholarship, Keble College
Evaporation (sometimes referred to as 'evapotranspiration') is the transfer of water vapour from the land surface into the atmosphere. Evaporation drives weather patterns, affecting cloud formation, convection and rainfall. In the Congo Basin, evaporation from the tropical rainforest to the north and from the deciduous savannah to the south is believed to provide up to 50% of the moisture that is returned to the surface as rainfall. Understanding the processes responsible for the seasonal cycle of evaporation is desirable, as these processes are likely to have important consequences for the seasonal differences in rainfall amount and distribution across the basin. However, the processes controlling this seasonal cycle have been understudied, owing to a lack of available observational data from flux towers.
In his doctoral research, David aims to examine reanalysis data to determine, in the absence of in situ observations, the dynamics which control the seasonal cycle of Congo Basin evaporation. He also seeks to identify weaknesses in how climate data products produce the evaporation, and suggest methods to rectify these weaknesses in future.
His first publication in Journal of Geophysical Research: Atmospheres examined the credibility of the evaporation produced in the Congo Basin by eleven global climate models. He found that the models which produce evaporation realistically against reliable reference data consistently produce less evaporation at the November rainfall peak than the March rainfall peak on the basin-wide average, because the models release less transpiration from the vegetation. He suggested that global climate models should include sub-grid rainfall schemes to ensure that they realistically represent the evaporation process. His second publication in Climate Dynamics explained that lower leaf area, a result of lower surface solar radiation, causes the difference in transpiration, and therefore evaporation, between the two rainfall peaks. His third publication aims to move towards an understanding of the dynamics controlling the full seasonal cycle of evaporation on the basin-wide average.
- Crowhurst, D., Dadson, S., Peng, J., and Washington, R. (2021) Contrasting controls on Congo Basin evaporation at the two rainfall peaks. Climate Dynamics, 56: 1609-1624.
- Crowhurst, D.M., Dadson, S.J. and Washington, R. (2020) Evaluation of Evaporation Climatology for the Congo Basin Wet Seasons in 11 Global Climate Models. Journal of Geophysical Research: Atmospheres, 125(6). e2019JD030619.