The RAS - Blackwell Prize
Winners of the Thesis Prizes, 2004: Biographies
(williams<-at->atm.ox.ac.uk; thesis studies in Atmospheric, Oceanic & Planetary Physics, Clarendon Laboratory, University of Oxford)
Nonlinear interactions of fast and slow modes in rotating, stratified fluid flows
I studied the behaviour of waves in the Earth's atmosphere. Rossby waves are responsible for the familiar pressure variations seen on weather maps, but the atmosphere also contains inertia-gravity waves, which are much smaller in wavelength. It was conventionally thought that Rossby waves and inertia-gravity waves did not significantly interact with each other. This was convenient for atmospheric modellers because inertia-gravity waves are too short to be explicitly included in computer models.
During my D.Phil. I used a laboratory experiment to show that inertia-gravity waves are actually able to cause major transitions in the spatial patterns of the Rossby waves. This was direct evidence that the interaction could be stronger than previously thought. I also showed that the transitions could be simulated in computer models by including a stochastic representation of the inertia-gravity waves. This finding adds to the evidence that numerical models of planetary atmospheres may be improved by adding random noise, a counter-intuitive concept that meteorologists are beginning to take seriously.
I currently hold a postdoctoral Research Fellowship in the Centre for Global Atmospheric Modelling at Reading University. My research forms part of a UK-wide programme which aims to improve our ability to quantify the probability and magnitude of future rapid changes in the Earth's climate. This involves a study of the physics not only of the atmosphere, but also of the ocean, and of interactions between the two. Of particular interest is the ocean's thermohaline circulation, which may rapidly collapse in response to anthropogenic greenhouse gas emissions.
(jwookey<-at->earth.leeds.ac.uk; thesis studies at the School of Earth Sciences, University of Leeds)
Modelling and interpreting seismograms for 3D Earth structure: A study of mid-mantle anisotropy
The research in my thesis concentrated on prospect of significant seismic anisotropy in the mid-Mantle region of the Earth. This region has long be considered isotropic, but recent global studies have shown widespread evidence that anisotropy is present on a large scale. My work concentrated on looking for evidence of mid-mantle anisotropy on a local scale using body-wave S-phases from deep Earthquakes in the Tonga-Kermadec subduction zones. I also developed and applied forward-modelling techniques to interpret the data. We found clear evidence of anisotropy attributable to the mid-mantle (most likely just below the 660 km discontinuity) for the first time in a local study.
Now a postdoc at School of Earth Sciences, University of Leeds, my main current research is still focussed on deep Earth anisotropy, but I am now working deeper still in the Earth on the enigmatic D" layer (the lowermost ~250 km of the mantle). We have developed techniques to make large improvements on the type of studies currently used to study anisotropy in this region, and have piloted these on a dataset from the Canadian National Seismic Network. This work has already produced some interesting results, and we hope to go on and apply this to a much larger, global dataset.