Transport, Stirring and Mixing
The transport, stirring and mixing of tracers is relevant to many applications of fluid dynamics and exploits much interesting mathematics. I am interested in some fundamental aspects of transport, stirring and mixing, as well as implications for atmospheric chemistry and oceanic biology.
There is much current interest on how changes to the stratosphere might affect the tropospheric circulation, or how prediction of changes to the tropospheric circulation might be limited by poor representation of the stratosphere in models. I have been investigating how dynamical sensitivity of the stratospheric circulation might allow changes imposed in the middle and upper stratosphere to penetrate downwards to the lower stratosphere and troposphere, and also how best to make quantitative predictions of the change in tropospheric circulation resulting from imposed perturbations (to the stratosphere or within the troposphere itself).
I am still working on the peculiar magnetostrophic fluid dynamics of the Sun's interior and on the great jetstreams in our atmosphere and oceans and on the planet Jupiter. For more detail, including the "hyperbalance equations" and a recent review written for plasma physicists interested in fusion power — and something on the recently-recognized DIMBO effect for ocean jets — see my home page: http://www.atm.damtp.cam.ac.uk/people/mem/.
Fluid Dynamics of the Ocean
I am particularly interested in ocean turbulence and mixing, ocean fronts and the surface boundary layer, and the impact of turbulence on micro-organisms. Recent work has uncovered a fascinating and poorly-understood collection of processes occurring at relatively small scales (<O(10km)) where the vertical motion is strong but stratification and the Earth's rotation are important factors. Since these motions are too small to be directly resolved by global ocean and climate models, understanding their impact on the structure and dynamics of the ocean is one of the most pressing topics in physical oceanography. Currently, I am studying upper ocean fronts and their impact on boundary layer turbulence, the role of physics in triggering phytoplankton blooms, the impact of turbulence on swimming bacteria, and mixing driven by breaking internal waves. My work primarily uses computational methods to address these questions.
When simulating large scale geophysical flows the effects of small scale turbulence must be parametrised because the resolution of any simulation is restricted by the available computational power. My current focus is to derive parametrisations of turbulence that conserve energy and momentum in order to increase the accuracy of these simulations.
The fluctuation-dissipation theorem relates the fluctuations present in a dynamical system to its response to a forcing. I am interested in extending the fluctuation-dissipation theorem with the eventual goal of applying it to estimate the future climate of the Earth. An intermediate goal is to test the fluctuation-dissipation theorem against climate models.
Mixing, Transport and Jets in the Southern Ocean
I am studying for my PhD as part of the international DIMES project — a large field program aimed at measuring mixing rates in the Southern Ocean, an area of extreme importance to ocean circulation and the earth system as a whole. Specifically, I am interested in looking at how mixing and transport varies around ocean jets near topography in the Southern Ocean, using both simplistic numerical models as well as large global circulation models such as the MITgcm. I am a joint student of the British Antarctic Survey in Polar Oceans group.
Extratropical Upper Troposphere/Lower Stratosphere Dynamics
The Upper Troposphere-Lower Stratosphere (UTLS) region is characterised by a strong connectivity between radiative, dynamical, chemical and microphysical processes and as a result is highly sensitive to climate change. A feature of the extratropical UTLS is the presence of a stable layer of air a few kilometers thick. This feature, named the tropopause inversion layer or TIL, was seen to emerge in observational studies using high vertical resolution radiosonde measurements after a specific type of averaging with respect to the tropopause is performed. I am currently extending the research done in my masters project and trying to model a TIL using a simplified global circulation model. My PhD work will involve studying the interactions in the UTLS with a particular focus on the chemistry. My PhD is joint with John Pyle's group at the Chemistry department.
Fluid Dynamics of Planetary Atmospheres
My PhD research focuses on the dynamics of atmospheres of planets other than the Earth with particular regard to both Jupiter and Mars. My research on Jupiter is currently concerned with the stability and driving mechanisms behind Jupiter's Zonal-Winds. I am using a shallow-water model with some simple forcing and damping to study how the jets on Jupiter are able to be quite as stable as we have observed them to be. I also have interests in the study of Mars' atmosphere, particularly its polar regions during the on-set and breakup of the polar vortex. Having undertaken work in my master's project with Professor Peter Read and Dr Luca Montabone whilst at the University of Oxford, I am hoping to continue working on the dynamics of the polar vortex, particularly during large dust storms. My work is in collaboration with the Astrophysical Fluid Dynamics group.