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PhD project on the dynamics of tropical convection and the large-scale tropical circulation

Job summary
Job summary
Sector Academic
Relevant divisions Atmospheric Sciences (AS)
Climate: Past, Present & Future (CL)
Type Full time
Level Entry level
Employer University of Leeds/Met Office
Location United Kingdom
Salary Open
Preferred education Master
Application deadline Open until the position is filled
Posted 29 November 2017
Job description

PhD project on the dynamics of tropical convection and the large-scale tropical circulation

University of Leeds / Met Office (UK applicants only)

We are looking for applicants with strong mathematical ability, for this PhD project which is available as part of the NERC DTP programme at the University of Leeds. The project would start 1 October 2018, and is supervised by Doug Parker, Juliane Schwendike (Leeds) and Lorenzo Tomassini (Met Office).

This project will advance our theoretical understanding of the most important dynamical processes in the tropical atmosphere, namely the interactions between convective clouds and their large-scale environment. This is one of the most critical unsolved theoretical questions in climate science, and we seek an ambitious and capable mathematician or physicist with an interest in solving real-world problems.

Deep convection in the tropics is the engine-room of the global climate, communicating energy, momentum and water between the major climatic systems (earth, atmosphere and ocean). Convection is really the driver of the tropical circulation, and tropical-extratropical transitions are important for weather prediction all over the globe. Convective clouds also deliver heavy rainfall and winds, and are the cause of much of the severe weather experienced in the tropics. Despite their importance, these clouds remain very poorly predicted, and their feedback on the climate system is one of the biggest uncertainties in weather and climate prediction. The project will use observations, numerical model simulations and mathematical theory to advance our understanding of how these storms interact with the circulation systems of the Earth’s tropics.

Water plays a remarkable role in the dynamics of the Earth’s atmosphere. Cumulonimbus storms are driven by the latent heat released during condensation as the air rises in the cloud. The mathematics of water vapour conversions in the atmosphere is deep and challenging. When phase changes of water occur, we have to deal with functional relationships which are highly nonlinear even non-differentiable. Once convective clouds have formed, they have a violent impact on atmospheric circulation. A cloud’s vertical velocities carry air through the depth of the troposphere in a few minutes, and lead to the generation of intense circulations (vorticity and potential vorticity) on the storm scale. In many parts of the world, those circulations lead to natural hazards such as tornados. The circulations also undergo complex fluid-dynamical transformations, including deformation, merging and “cascades” between spatial scales, so that the effects of a single storm on the 10km scale influence the environment on continental scales of 1000s of km. The mathematics of these systems is under-explored.

It is not just latent heating in clouds which contributes to storm intensity. Cooling of the air by evaporation of falling precipitation (snow or rain) can lead to intense downdraughts, which cause severe wind squalls when they descend to the Earth’s surface and spread out laterally. Other processes such as long-wave radiation from the cloud-tops, also contribute to the instability which drives the convection. A key uncertainty in climate science is to understand how such processes will change in a future climate, when the long-wave radiation changes, and the warmer air is able to hold more water vapour.

The project will explore theoretical approaches to these problems. It will exploit the new generation of numerical modelling products, in the form of very high resolution atmospheric simulations with an operational weather prediction model, to test and develop mathematical models. We have some nice tools to use to analyse the model data, including the analysis of Lagrangian “PV tracers” and the use of storm tracking. We also have access to the latest generation of satellite measurements of tropical clouds, and data from recent field experiments in Africa and India. We aim to use these model and observational data to test and advance theoretical understanding of the tropical dynamics.

This PhD project is a new collaborative research venture between the supervisors, who are based in School of Earth and Environment and at Leeds and the Met Office. Through partnership with the Met Office, results of the project will be communicated to, and hopefully influence the community of scientists developing the next generation of weather and climate models. We aim that this project will develop advanced theoretical understanding of water vapour processes in tropical storms and circulations, with practical applicability.

Requirements:
Strong mathematical background, e.g. excellent first degree or Master’s degree in Mathematics or Physics.

If you are interested, please get in touch with the supervisors,
Doug Parker <d.j.parker@leeds.ac.uk>
Juliane Schwendike <J.Schwendike@leeds.ac.uk>
Lorenzo Tomassini <lorenzo.tomassini@metoffice.gov.uk>

Interviews will take place in March 2018.

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