Research

Jones

With postgrads Sleep and Underwood, examining whether Earth-analogues in the habitable zone (HZ) can survive the gravitational buffeting of the giant planet(s) during the main-sequence lifetime of the exosystem's star, rather than being removed from the HZ perhaps colliding with the star or a giant planet. By studying representative systems in great detail, establishing simple criteria for orbital stability, and assessing the habitability of all known exoplanetary systems.

The figure shows the habitable zone of HD73526 and the giant planet's gravitational reach (at 1.3 times minimum giant mass), extending to 2.5 Hill radii inside its periastron and 8 Hil radii outside its apastron.

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Haswell

With postgrad Enoch, working with other members of the WASP consortium to develop a sophisticated automated pipeline reduction system to process data from the Wide Area Search for Planets in order to discover tens of transitting extrasolar planets over the next few years.

The image shows the SuperWASP telescope on La Palma, in its 5 camera configuration during 2004

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Lewis

Modelling planetary atmospheres and climates

Planetary atmospheres, oceans and even fluid interiors, are examples of stratified fluids, moving under the influence of rotation. Motions are driven ultimately by buoyancy forces generated by differential heating and cooling. These are highly complex, nonlinear systems and are generally coupled with many feedbacks within the whole climate system. Models are employed in order to conduct experiments and to test hypotheses on such systems. These models range from relatively simple process models to full simulations on supercomputers, such as may be employed for weather forecasting or for climate prediction on Earth. A full hierarchy of models is important for developing an understanding of the processes involved and for interpreting and testing the most complex of the models, known as general circulation models (GCMs).

Research in this area involves modelling the atmospheres of several different planets, and of the Earth itself in the distant past. The atmospheres of other planets are intriguing as diverse systems in their own right and an improved understanding may be vital in planning future spacecraft missions, e.g. to Mars. In addition, modelling other planets and paleoclimates offers the opportunity to test the same techniques employed to model the present day weather and climate of the Earth under a range of more extreme conditions.

The figure shows the north pole of Mars, showing several dust storms around the edge of the polar ice cap.

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Mars

A Mars general circulation model has been developed over more than ten years, initially based at Oxford University and involving collaboration with researchers at Laboratoire de M鴩orologie Dynamique (LMD) du CNRS in Paris and Istituto de Astrofisica de Andalucia in Spain. Current research topics include:

Venus and Titan

A Venus GCM with simplified physical schemes is presently under development. Research topics include an investigation of the remarkable atmospheric super-rotation on this slowly rotating planet; the atmosphere at the level of the cloud decks rotates sixty times faster than the underlying solid surface.

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Giant planets and exoplanets

Simpler, reduced physics models have been developed of limited regions in the upper tropospheres of the giant planets, investigating long-lived eddies, such as Jupiter's Great Red Spot, and the processes which govern the spacing of the belts and zones. In addition to numerical modelling, laboratory analogues have been investigated, employing fluids in rotating containers with similar ranges of parameters.

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Terrestrial paleoclimate

In the distant past (several 100 million years before the present) there is evidence that the Earth has experienced both extremely warm and cold climates, including the possibility of an almost totally frozen, ?Snowball Earth?. A modern coupled ocean-atmosphere climate model has been used to investigate the stability of such states, far removed from the climate experienced in the last few thousand years.

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