I currently have positions open for PhD students and honours students to work on a range of projects broadly concerning the dynamics of the tropical atmosphere. Some potential projects are outlined below, but please contact me if you are interested in working in my group. Details on the PhD application process at Monash Univeristy may be found here.
Click on the project titles below to see a description of each project.
Tropical convection and thunderstorms
Understanding the land-ocean contrast in tropical convective intensity
The intensity of tropical thunderstorms is much higher over land than over the ocean. This land-ocean difference is evident in satellite estimates of lightning frequency, and it is has been found in measures of convective intensity derived from ground- and space-based radars. While there are a number of hypotheses that seek to explain the land-ocean contrast in the strength of thunderstorms, a clear understanding of their relative importance remains unknown. In this project, will use a combination of idealised numerical simulations and observational analyses in order to systematically investigate different causes of convective enhancement that have been hypothesised to be important for observed convection over land. This project is suitable for a PhD student with a strong mathematical and computational background.
Intense tropical thunderstorms in a future warmer world
Climate models predict that the energy available to tropical thunderstorms will increase under a future warmer climate. However, the mechanisms that lead to this increase in potential energy, and its implications for tropical thunderstorms remain incomplete. This project will use a combination of observational analysis and high-resolution modelling to investigate the mechanisms that influence tropical thunderstorm intensity as the climate warms. In particular, it will focus on a recently proposed theory for the energy available to tropical thunderstorms that depends on the rate of mixing of clouds and their unsaturated environment. This project is suitable for a PhD student with strong mathematical and computational skills.
Characterising intense convection in the tropics
A large fraction of the most intense thunderstorms on Earth occurs in the tropics and subtropics; many of these storms are part of larger systems that can be organised on mesoscales or larger scales. However, our understanding of the relationships between intense and organised convection and the large-scale environment is lacking, particularly in the tropics. In this project, we will use satellite data to probe the relationships between convective organisation, convective intensity, and the large-scale state of the atmosphere across tropical land and ocean. This project is suitable for an honours or PhD student with strong coding skills.
Large-scale tropical circulations and the monsoon
Dynamical constraints on the tropical overturning circulation
One of the most important features of the atmospheric general circulation is the Hadley circulation, a large-scale overturning that consists of rising motion in the deep tropics and descending motion in the subtropics. These motions are responsible for a band of high precipitation near the equator called the Intertropical Convergence Zone (ITCZ) and for the existence of deserts in Earth's subtropical regions. The seasonal shifts of the Hadley circulation are associated with Earth's monsoons, which provide seasonal precipitation for a large fraction ofthe world's population.
Despite the importance of the tropical overturning circulation, our understanding of the factors governing its strength and seasonal extent remain incomplete. For instance, climate models produce Hadley circulations with a wide variety of strengths, and constraining the strength of the Hadley circulation with observations has proven difficult. In this project, we will use a numerical model to simulate idealised tropical overturning circulations over a wide range of climatic conditions in order to develop and test theories for the tropical overturning circulatio for its position and strength as a function of external parameters such as the rotation rate, solar insolation gradient and the global mean temperature. A strong mathematical background is essential for this project to be sucessful.
Earth's monsoons in the past, present and future
A large proportion of the world's population depends on seasonal rainfall delivered by large-scale tropical circulations known as monsoons. However, future predictions of monsoons, and tropcal precipitation more generally, differ considerably across different climate models. Additionally, climate models cannot quantitatively reproduce known past variations in monsoon rainfall inferred from environmental proxies. One possible reason for this model deficiency is that global climate models have difficulty simulating small-scale circulations associated with convective clouds, and these small-scale circulations have important effects on the large-scale flow. In this project, we will use a numerical model to investigate the role that small-scale circulations associated with convection play in determining the large-scale climate in monsoon regions. In particular, the potential role of the diurnal cycle of convection in determing the strength and position of the monsoon will be investigated. This project is suitable for a PhD student with a stong mathematical and computational background.
Understanding trends in tropical upper-tropospheric temperature
Climate models predict that the temperature of the tropical upper troposphere will warm faster than the surface in response to increased greenhouse-gas concentrations. However, this upper tropospheric “amplification" of warming is weaker or not present in many observational datasets. Furthermore, the degree of amplification varies substantially across different climate models used in the IPCC assessments. This project will seek to understand the origin of these differences by examining the output of climate models and comparing this output to a simple theoretical prediction for the tropical temperature profile. We will examine to what extent different assumptions used in the theoretical model can explain the different amplification factors among climate models. Furthermore, we will investigate the sensitivity of the upper-tropospheric warming pattern to different patterns of surface warming and to different physical processes. This project is suitable for an honours or PhD student with a strong mathematical background.
