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The role of diabatic processes during the intensification of tropical cyclones

Dr Juliane Schwendike (SEE), Dr Andrew Ross (SEE), Christopher Short (Met Office)

Project partner(s):  Met Office (Potential CASE)

Contact email: j.schwendike@leeds.ac.uk

Project description / Motivation

Tropical cyclones are one of the most destructive atmospheric phenomena. Each year they cause enormous amounts of damage due to their destructive winds, heavy precipitation and their effects on the sea, e.g. storm surges. Two particularly intense tropical cyclones have recently affected the Philippines. In 2013, Typhoon Haiyan killed over 6,300 people and caused 1.8 billion pounds in total damage. Haiyan was one of the strongest tropical cyclones on record with one-minute sustained near-surface wind speeds of 315 km h-1 (195 mph). In December of the following year, Typhoon Hagupit killed 18 people and caused £71 million of damage to infrastructure and agriculture. Typhoon Megi (2016) which made landfall in Taiwan, is another recent example (Fig. 1). Being able to accurately forecast the track and intensity of these high impact weather systems is crucial to enable people to take appropriate action in time to minimise the damage to livelihood, property and economy.

Fig. 1: Typhoon Megi on 26 September 2016 at 0425 UTC taken from the Visible Infrared Imaging Radiometer Suite (VIIRS). Image Courtesy: NASA (http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=88820).

The largest number of tropical cyclones can be found in the Western Pacific. Here, tropical cyclones often rapidly intensify from a tropical depression to a Category 5 typhoon (1-minute surface wind speeds larger than 157 mph / 137 kt / 252 km h-1) in a few days. How this happens is one of the most challenging unanswered questions about tropical cyclones today. This project aims to investigate the dynamics of rapid intensification and how the underlying processes are represented in a world-class numerical weather prediction model, the Met Office Unified Model (MetUM). The main focus is to investigate the link between physical processes occurring in the inner regions of tropical cyclones and rapid intensification. One way to do this is by using potential vorticity (PV) tracers and calculating potential temperature and PV budgets. PV is a particularly useful diagnostic as it links the dynamics and thermodynamics.

Objectives

The scientific objectives of the PhD project are:

  1. What role do inner core processes play in the rapid intensification of tropical cyclones?

  2. What impact do these processes have on the cyclone track?

  3. How are these process represented in the MetUM?

  4. Develop diagnostic evaluation tools to assess the 3-dimensional structure and dynamics of tropical cyclones in the MetUM.

Potential for high-impact outcome

The Met Office has a close working relationship with the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA). The Philippines are severely affected by the most intense tropical cyclones. Forecasting the track and intensity of these storms is a key challenge for numerical weather prediction models such as the MetUM, in both global and regional configurations. This project provides a way to investigate one aspect of the intensification of tropical cyclones and to identify what is needed to represent the underlying processes in the MetUm in order improve our ability to forecast these storms more accurately, ultimately benefiting people at risk. Close collaboration with the Met Office will ensure the results of this study will feed into model development. The outcome of this study may also provide guidance for forecasters. The project will generate results for several papers, with at least one being suitable for submission to a high impact journal.

Training

The student will work under the supervision of Dr Juliane Schwendike and Dr Andrew Ross from the University of Leeds, as well as Dr Christopher Short from the Met Office. Co-supervision will involve regular meetings between all partners and regular visits to the Met Office in Exeter. The student might have the opportunity to visit PAGASA in the Philippines and Monash University in Australia. The successful PhD student will have access to a broad spectrum of training in numerical modelling, through to managing your degree or to preparing for your viva (http://www.emeskillstraining.leeds.ac.uk/). This project provides a high level of specialist scientific training in:

  1. Numerical modelling and use of cutting-edge supercomputers;

  2. Analysis of in-situ measurements from aircraft and ground-based monitoring sites;

  3. State-of-the-science application and analysis of global atmospheric reanalysis data;

  4. A computer programming language (e.g. Python) to perform complex analysis techniques;

  5. Effective written and oral communication skills.

The student will be part of the Dynamics and Clouds Group, which is embedded in the Institute for Climate and Atmospheric Science (ICAS) within the School of Earth and Environment. The Dynamics and Clouds Group is a large and active group of people working on a range of problems, with particular interests in the tropics and the role of convection. The group meets regularly and these group meeting provide an excellent opportunity to discuss your work  as well as to learn more about what others are working on. We encourage you to be an active member of the Dynamics and Clouds Group.

Related undergraduate subjects:

  • Physical science