Investigating the dynamics of rapidly intensifying tropical cyclones in Southeast Asia (CASE award)

Year
2024
Primary Supervisor
Juliane Schwendike <j.schwendike@leeds.ac.uk>
Institution
University of Leeds (School of Earth and Environment))
Possibility of becoming a CASE project.
Yes
Academic Supervisors
Dr Andrew Ross <A.N.Ross@leeds.ac.uk> (University of leeds, Earth and Environment), Richard Jones
Research Themes
Project Partners
Met Office
Research Keywords
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Relevant Degree Courses
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Project description

Tropical cyclones (TCs) are amongst the most hazardous severe weather events in the tropics. Forecasts of TC tracks have improved in recent years (Heming et al., 2016), enabling earlier warnings and allowing better preparations to be made ahead of landfall. However, while forecasts of TC intensity from global numerical weather predictions (NWP) models have improved, this has been slower than for TC track forecasts (De Maria et al., 2014).

Fig. 1: Satellite image of Super Typhoon Rai on 06 December 2021. Image Courtesy: NASA (https://earthobservatory.nasa.gov/images/149228/super-typhoon-rai).

Forecasting rapid intensification (RI) events, where maximum wind speeds increase by 30 knots in a 24-hour period (Kaplan and DeMaria, 2002), remain challenging for both global and regional NWP models. The mesoscale processes responsible for RI, such as eyewall replacement cycles, are not captured by operational global NWP models. Convection-permitting regional models are able to capture these processes better but struggle to predict the timing and magnitude of RI (Short and Petch, 2018).

With growing capability in high-resolution regional coupled simulations (Castillo et al., 2022) we can explore the sensitivity of RI events to atmosphere-ocean coupling. This studentship will investigate rapidly intensifying TCs in Southeast Asia, and improve our understanding of the underlying processes responsible for RI in an ensemble framework. Further, there will be analysis of the sensitivity of TC intensity forecasts to atmosphere-ocean coupling utilising convection-permitting ensemble simulations.

Objectives

The scientific objectives of the PhD project are:

  1. Conduct a detailed investigation into the processes that lead to rapid intensification of tropical cyclones;
  2. Develop an understanding of the model’s limitations and investigate ways to improve it.

In particular, according to your particular research interests, the studentship could involve the following:

Year 1: Atmosphere-land only coupling

  • Evaluate ensemble simulations of rapidly intensifying high impact TCs in Southeast Asia including for instance Typhoons Goni (2020), Rai (2020; Fig. 1) and Noru (2022).
  • Compare MetUM simulations with observations to assess if the simulations are able to accurately capture RI events.

Year 2: Atmosphere-land and ocean coupling

  • Investigate coupled simulations of the same set of impactful events with a focus on the sensitivity of TC intensity to atmosphere-ocean coupling.
  • Are the coupled simulations more/less able to capture RI events?
  • Are the forecast track and forward speed of the TC impacted by the atmosphere-ocean coupling?

Year 3: Land-atmosphere interactions

  • You will have more freedom to explore the rich data sets and may chose to focus on one particularly interesting or impactful storm.
  • An area of interest to the WCSSP Southeast Asia partners (the national weather services in the Philippines, Malaysia, Indoensia, and Vietnam) is the impact of precipitation at landfall, particularly its spatial distribution and any asymmetry.

You will have the opportunity to spend time at the Met Office and learn how to run regional model simulations.

Potential for high-impact outcome

The Met Office has a close working relationship with the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) and the National Center for Hydrometeorological Forecasting (NCHMF) in Vietnam. The Philippines and Vietnam are severely affected by the most intense TCs. Forecasting the track and intensity of these storms is a key challenge for NWP models such as the MetUM, in both global and regional configurations. This project provides a way to investigate aspects of the TC dynamics in detail, to evaluate how certain dynamical processes are represented in the model with the aim of improving our ability to forecast these storms more accurately, ultimately benefiting people at risk. 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 be able to visit the Met Office in Exeter regularly and will have access to a broad spectrum of training in:

  • Numerical modelling and use of cutting-edge supercomputers;
  • State-of-the-science application and analysis of global atmospheric reanalysis data;
  • A computer programming language (e.g. Python) to perform complex analysis techniques;
  • Effective written and oral communication skills.

Further reading

Chan, J. C. L., and J. D. Kepert (2010). Global perspectives on tropical cyclones. World Scientific.

Emanuel, K. (2003). Tropical Cyclones. Annual Review of Earth and Planetary Sciences, 31, 75-104.

Stull, R. (1997). Introduction to boundary layer meteorology, Kluwer Academic Publishers.